[lldb][NFC] Remove WordComplete mode, make result array indexed from 0 and remove any undocumented/redundant return values

Summary:
We still have some leftovers of the old completion API in the internals of
LLDB that haven't been replaced by the new CompletionRequest. These leftovers
are:

* The return values (int/size_t) in all completion functions.
* Our result array that starts indexing at 1.
* `WordComplete` mode.

I didn't replace them back then because it's tricky to figure out what exactly they
are used for and the completion code is relatively untested. I finally got around
to writing more tests for the API and understanding the semantics, so I think it's
a good time to get rid of them.

A few words why those things should be removed/replaced:

* The return values are really cryptic, partly redundant and rarely documented.
  They are also completely ignored by Xcode, so whatever information they contain will end up
  breaking Xcode's completion mechanism. They are also partly impossible to even implement
  as we assign negative values special meaning and our completion API sometimes returns size_t.

  Completion functions are supposed to return -2 to rewrite the current line. We seem to use this
  in some untested code path to expand the history repeat character to the full command, but
  I haven't figured out why that doesn't work at the moment.
  Completion functions return -1 to 'insert the completion character', but that isn't implemented
  (even though we seem to activate this feature in LLDB sometimes).
  All positive values have to match the number of results. This is obviously just redundant information
  as the user can just look at the result list to get that information (which is what Xcode does).

* The result array that starts indexing at 1 is obviously unexpected. The first element of the array is
  reserved for the common prefix of all completions (e.g. "foobar" and "footar" -> "foo"). The idea is
  that we calculate this to make the life of the API caller easier, but obviously forcing people to have
  1-based indices is not helpful (or even worse, forces them to manually copy the results to make it
  0-based like Xcode has to do).

* The `WordComplete` mode indicates that LLDB should enter a space behind the completion. The
  idea is that we let the top-level API know that we just provided a full completion. Interestingly we
  `WordComplete` is just a single bool that somehow represents all N completions. And we always
  provide full completions in LLDB, so in theory it should always be true.
  The only use it currently serves is providing redundant information about whether we have a single
  definitive completion or not (which we already know from the number of results we get).

This patch essentially removes `WordComplete` mode and makes the result array indexed from 0.
It also removes all return values from all internal completion functions. The only non-redundant information
they contain is about rewriting the current line (which is broken), so that functionality was moved
to the CompletionRequest API. So you can now do `addCompletion("blub", "description", CompletionMode::RewriteLine)`
to do the same.

For the SB API we emulate the old behaviour by making the array indexed from 1 again with the common
prefix at index 0. I didn't keep the special negative return codes as we either never sent them before (e.g. -2) or we
didn't even implement them in the Editline handler (e.g. -1).

I tried to keep this patch minimal and I'm aware we can probably now even further simplify a bunch of related code,
but I would prefer doing this in follow-up NFC commits

Reviewers: JDevlieghere

Reviewed By: JDevlieghere

Subscribers: arphaman, abidh, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D66536

llvm-svn: 369624

34 files changed, 344 insertions, 478 deletions

diff --git a/lldb/source/API/SBCommandInterpreter.cpp b/lldb/source/API/SBCommandInterpreter.cpp
index ccc70b3ccdb..98354c414a7 100644
--- a/lldb/source/API/SBCommandInterpreter.cpp
+++ b/lldb/source/API/SBCommandInterpreter.cpp
@@ -353,8 +353,6 @@ int SBCommandInterpreter::HandleCompletionWithDescriptions(
                      current_line, cursor, last_char, match_start_point,
                      max_return_elements, matches, descriptions);
 
-  int num_completions = 0;
-
   // Sanity check the arguments that are passed in: cursor & last_char have to
   // be within the current_line.
   if (current_line == nullptr || cursor == nullptr || last_char == nullptr)
@@ -368,22 +366,50 @@ int SBCommandInterpreter::HandleCompletionWithDescriptions(
       last_char - current_line > static_cast<ptrdiff_t>(current_line_size))
     return 0;
 
+  if (!IsValid())
+    return 0;
 
-  if (IsValid()) {
-    lldb_private::StringList lldb_matches, lldb_descriptions;
-    CompletionResult result;
-    CompletionRequest request(current_line, cursor - current_line, result);
-    num_completions = m_opaque_ptr->HandleCompletion(request);
-    result.GetMatches(lldb_matches);
-    result.GetDescriptions(lldb_descriptions);
-
-    SBStringList temp_matches_list(&lldb_matches);
-    matches.AppendList(temp_matches_list);
-    SBStringList temp_descriptions_list(&lldb_descriptions);
-    descriptions.AppendList(temp_descriptions_list);
+  lldb_private::StringList lldb_matches, lldb_descriptions;
+  CompletionResult result;
+  CompletionRequest request(current_line, cursor - current_line, result);
+  m_opaque_ptr->HandleCompletion(request);
+  result.GetMatches(lldb_matches);
+  result.GetDescriptions(lldb_descriptions);
+
+  // Make the result array indexed from 1 again by adding the 'common prefix'
+  // of all completions as element 0. This is done to emulate the old API.
+  if (request.GetParsedLine().GetArgumentCount() == 0) {
+    // If we got an empty string, insert nothing.
+    lldb_matches.InsertStringAtIndex(0, "");
+    lldb_descriptions.InsertStringAtIndex(0, "");
+  } else {
+    // Now figure out if there is a common substring, and if so put that in
+    // element 0, otherwise put an empty string in element 0.
+    std::string command_partial_str = request.GetCursorArgumentPrefix().str();
+
+    std::string common_prefix = lldb_matches.LongestCommonPrefix();
+    const size_t partial_name_len = command_partial_str.size();
+    common_prefix.erase(0, partial_name_len);
+
+    // If we matched a unique single command, add a space... Only do this if
+    // the completer told us this was a complete word, however...
+    if (lldb_matches.GetSize() == 1) {
+      char quote_char = request.GetParsedArg().quote;
+      common_prefix =
+          Args::EscapeLLDBCommandArgument(common_prefix, quote_char);
+      if (request.GetParsedArg().IsQuoted())
+        common_prefix.push_back(quote_char);
+      common_prefix.push_back(' ');
+    }
+    lldb_matches.InsertStringAtIndex(0, common_prefix.c_str());
+    lldb_descriptions.InsertStringAtIndex(0, "");
   }
 
-  return num_completions;
+  SBStringList temp_matches_list(&lldb_matches);
+  matches.AppendList(temp_matches_list);
+  SBStringList temp_descriptions_list(&lldb_descriptions);
+  descriptions.AppendList(temp_descriptions_list);
+  return result.GetNumberOfResults();
 }
 
 int SBCommandInterpreter::HandleCompletionWithDescriptions(
diff --git a/lldb/source/Commands/CommandCompletions.cpp b/lldb/source/Commands/CommandCompletions.cpp
index 1cff39c3734..a06f9a4db53 100644
--- a/lldb/source/Commands/CommandCompletions.cpp
+++ b/lldb/source/Commands/CommandCompletions.cpp
@@ -71,10 +71,9 @@ bool CommandCompletions::InvokeCommonCompletionCallbacks(
   return handled;
 }
 
-int CommandCompletions::SourceFiles(CommandInterpreter &interpreter,
-                                    CompletionRequest &request,
-                                    SearchFilter *searcher) {
-  request.SetWordComplete(true);
+void CommandCompletions::SourceFiles(CommandInterpreter &interpreter,
+                                     CompletionRequest &request,
+                                     SearchFilter *searcher) {
   // Find some way to switch "include support files..."
   SourceFileCompleter completer(interpreter, false, request);
 
@@ -85,12 +84,11 @@ int CommandCompletions::SourceFiles(CommandInterpreter &interpreter,
   } else {
     completer.DoCompletion(searcher);
   }
-  return request.GetNumberOfMatches();
 }
 
-static int DiskFilesOrDirectories(const llvm::Twine &partial_name,
-                                  bool only_directories, StringList &matches,
-                                  TildeExpressionResolver &Resolver) {
+static void DiskFilesOrDirectories(const llvm::Twine &partial_name,
+                                   bool only_directories, StringList &matches,
+                                   TildeExpressionResolver &Resolver) {
   matches.Clear();
 
   llvm::SmallString<256> CompletionBuffer;
@@ -98,7 +96,7 @@ static int DiskFilesOrDirectories(const llvm::Twine &partial_name,
   partial_name.toVector(CompletionBuffer);
 
   if (CompletionBuffer.size() >= PATH_MAX)
-    return matches.GetSize();
+    return;
 
   namespace path = llvm::sys::path;
 
@@ -129,7 +127,7 @@ static int DiskFilesOrDirectories(const llvm::Twine &partial_name,
           matches.AppendString(Resolved);
         }
       }
-      return matches.GetSize();
+      return;
     }
 
     // If there was no trailing slash, then we're done as soon as we resolve
@@ -139,7 +137,7 @@ static int DiskFilesOrDirectories(const llvm::Twine &partial_name,
       // Make sure it ends with a separator.
       path::append(CompletionBuffer, path::get_separator());
       matches.AppendString(CompletionBuffer);
-      return matches.GetSize();
+      return;
     }
 
     // We want to keep the form the user typed, so we special case this to
@@ -221,49 +219,44 @@ static int DiskFilesOrDirectories(const llvm::Twine &partial_name,
 
     matches.AppendString(CompletionBuffer);
   }
-
-  return matches.GetSize();
 }
 
-static int DiskFilesOrDirectories(CompletionRequest &request,
-                                  bool only_directories) {
-  request.SetWordComplete(false);
+static void DiskFilesOrDirectories(CompletionRequest &request,
+                                   bool only_directories) {
   StandardTildeExpressionResolver resolver;
   StringList matches;
   DiskFilesOrDirectories(request.GetCursorArgumentPrefix(), only_directories,
                          matches, resolver);
   request.AddCompletions(matches);
-  return request.GetNumberOfMatches();
 }
 
-int CommandCompletions::DiskFiles(CommandInterpreter &interpreter,
-                                  CompletionRequest &request,
-                                  SearchFilter *searcher) {
-  return DiskFilesOrDirectories(request, /*only_dirs*/ false);
+void CommandCompletions::DiskFiles(CommandInterpreter &interpreter,
+                                   CompletionRequest &request,
+                                   SearchFilter *searcher) {
+  DiskFilesOrDirectories(request, /*only_dirs*/ false);
 }
 
-int CommandCompletions::DiskFiles(const llvm::Twine &partial_file_name,
-                                  StringList &matches,
-                                  TildeExpressionResolver &Resolver) {
-  return DiskFilesOrDirectories(partial_file_name, false, matches, Resolver);
+void CommandCompletions::DiskFiles(const llvm::Twine &partial_file_name,
+                                   StringList &matches,
+                                   TildeExpressionResolver &Resolver) {
+  DiskFilesOrDirectories(partial_file_name, false, matches, Resolver);
 }
 
-int CommandCompletions::DiskDirectories(CommandInterpreter &interpreter,
-                                        CompletionRequest &request,
-                                        SearchFilter *searcher) {
-  return DiskFilesOrDirectories(request, /*only_dirs*/ true);
+void CommandCompletions::DiskDirectories(CommandInterpreter &interpreter,
+                                         CompletionRequest &request,
+                                         SearchFilter *searcher) {
+  DiskFilesOrDirectories(request, /*only_dirs*/ true);
 }
 
-int CommandCompletions::DiskDirectories(const llvm::Twine &partial_file_name,
-                                        StringList &matches,
-                                        TildeExpressionResolver &Resolver) {
-  return DiskFilesOrDirectories(partial_file_name, true, matches, Resolver);
+void CommandCompletions::DiskDirectories(const llvm::Twine &partial_file_name,
+                                         StringList &matches,
+                                         TildeExpressionResolver &Resolver) {
+  DiskFilesOrDirectories(partial_file_name, true, matches, Resolver);
 }
 
-int CommandCompletions::Modules(CommandInterpreter &interpreter,
-                                CompletionRequest &request,
-                                SearchFilter *searcher) {
-  request.SetWordComplete(true);
+void CommandCompletions::Modules(CommandInterpreter &interpreter,
+                                 CompletionRequest &request,
+                                 SearchFilter *searcher) {
   ModuleCompleter completer(interpreter, request);
 
   if (searcher == nullptr) {
@@ -273,13 +266,11 @@ int CommandCompletions::Modules(CommandInterpreter &interpreter,
   } else {
     completer.DoCompletion(searcher);
   }
-  return request.GetNumberOfMatches();
 }
 
-int CommandCompletions::Symbols(CommandInterpreter &interpreter,
-                                CompletionRequest &request,
-                                SearchFilter *searcher) {
-  request.SetWordComplete(true);
+void CommandCompletions::Symbols(CommandInterpreter &interpreter,
+                                 CompletionRequest &request,
+                                 SearchFilter *searcher) {
   SymbolCompleter completer(interpreter, request);
 
   if (searcher == nullptr) {
@@ -289,12 +280,11 @@ int CommandCompletions::Symbols(CommandInterpreter &interpreter,
   } else {
     completer.DoCompletion(searcher);
   }
-  return request.GetNumberOfMatches();
 }
 
-int CommandCompletions::SettingsNames(CommandInterpreter &interpreter,
-                                      CompletionRequest &request,
-                                      SearchFilter *searcher) {
+void CommandCompletions::SettingsNames(CommandInterpreter &interpreter,
+                                       CompletionRequest &request,
+                                       SearchFilter *searcher) {
   // Cache the full setting name list
   static StringList g_property_names;
   if (g_property_names.GetSize() == 0) {
@@ -309,44 +299,29 @@ int CommandCompletions::SettingsNames(CommandInterpreter &interpreter,
     }
   }
 
-  bool exact_match = false;
-
   for (const std::string &s : g_property_names) {
-    if (llvm::StringRef(s).startswith(request.GetCursorArgumentPrefix())) {
-      if (request.GetCursorArgumentPrefix() == s)
-        exact_match = true;
+    if (llvm::StringRef(s).startswith(request.GetCursorArgumentPrefix()))
       request.AddCompletion(s);
-    }
   }
-
-  request.SetWordComplete(exact_match);
-
-  return request.GetNumberOfMatches();
 }
 
-int CommandCompletions::PlatformPluginNames(CommandInterpreter &interpreter,
-                                            CompletionRequest &request,
-                                            SearchFilter *searcher) {
-  StringList new_matches;
-  std::size_t num_matches = PluginManager::AutoCompletePlatformName(
-      request.GetCursorArgumentPrefix(), new_matches);
-  request.SetWordComplete(num_matches == 1);
-  request.AddCompletions(new_matches);
-  return request.GetNumberOfMatches();
+void CommandCompletions::PlatformPluginNames(CommandInterpreter &interpreter,
+                                             CompletionRequest &request,
+                                             SearchFilter *searcher) {
+  PluginManager::AutoCompletePlatformName(request.GetCursorArgumentPrefix(),
+                                          request);
 }
 
-int CommandCompletions::ArchitectureNames(CommandInterpreter &interpreter,
-                                          CompletionRequest &request,
-                                          SearchFilter *searcher) {
-  const uint32_t num_matches = ArchSpec::AutoComplete(request);
-  request.SetWordComplete(num_matches == 1);
-  return num_matches;
+void CommandCompletions::ArchitectureNames(CommandInterpreter &interpreter,
+                                           CompletionRequest &request,
+                                           SearchFilter *searcher) {
+  ArchSpec::AutoComplete(request);
 }
 
-int CommandCompletions::VariablePath(CommandInterpreter &interpreter,
-                                     CompletionRequest &request,
-                                     SearchFilter *searcher) {
-  return Variable::AutoComplete(interpreter.GetExecutionContext(), request);
+void CommandCompletions::VariablePath(CommandInterpreter &interpreter,
+                                      CompletionRequest &request,
+                                      SearchFilter *searcher) {
+  Variable::AutoComplete(interpreter.GetExecutionContext(), request);
 }
 
 CommandCompletions::Completer::Completer(CommandInterpreter &interpreter,
@@ -417,15 +392,14 @@ CommandCompletions::SourceFileCompleter::SearchCallback(SearchFilter &filter,
   return Searcher::eCallbackReturnContinue;
 }
 
-size_t
-CommandCompletions::SourceFileCompleter::DoCompletion(SearchFilter *filter) {
+void CommandCompletions::SourceFileCompleter::DoCompletion(
+    SearchFilter *filter) {
   filter->Search(*this);
   // Now convert the filelist to completions:
   for (size_t i = 0; i < m_matching_files.GetSize(); i++) {
     m_request.AddCompletion(
         m_matching_files.GetFileSpecAtIndex(i).GetFilename().GetCString());
   }
-  return m_request.GetNumberOfMatches();
 }
 
 // SymbolCompleter
@@ -489,13 +463,11 @@ Searcher::CallbackReturn CommandCompletions::SymbolCompleter::SearchCallback(
   return Searcher::eCallbackReturnContinue;
 }
 
-size_t CommandCompletions::SymbolCompleter::DoCompletion(SearchFilter *filter) {
+void CommandCompletions::SymbolCompleter::DoCompletion(SearchFilter *filter) {
   filter->Search(*this);
   collection::iterator pos = m_match_set.begin(), end = m_match_set.end();
   for (pos = m_match_set.begin(); pos != end; pos++)
     m_request.AddCompletion((*pos).GetCString());
-
-  return m_request.GetNumberOfMatches();
 }
 
 // ModuleCompleter
@@ -536,7 +508,6 @@ Searcher::CallbackReturn CommandCompletions::ModuleCompleter::SearchCallback(
   return Searcher::eCallbackReturnContinue;
 }
 
-size_t CommandCompletions::ModuleCompleter::DoCompletion(SearchFilter *filter) {
+void CommandCompletions::ModuleCompleter::DoCompletion(SearchFilter *filter) {
   filter->Search(*this);
-  return m_request.GetNumberOfMatches();
 }
diff --git a/lldb/source/Commands/CommandObjectCommands.cpp b/lldb/source/Commands/CommandObjectCommands.cpp
index 65fc8869edf..4eb438f2b96 100644
--- a/lldb/source/Commands/CommandObjectCommands.cpp
+++ b/lldb/source/Commands/CommandObjectCommands.cpp
@@ -215,13 +215,12 @@ public:
     return "";
   }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eDiskFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
   Options *GetOptions() override { return &m_options; }
@@ -1388,13 +1387,12 @@ public:
 
   ~CommandObjectCommandsScriptImport() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eDiskFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
   Options *GetOptions() override { return &m_options; }
diff --git a/lldb/source/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index 46f12d8685b..79003d324c6 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -294,7 +294,7 @@ CommandObjectExpression::~CommandObjectExpression() = default;
 
 Options *CommandObjectExpression::GetOptions() { return &m_option_group; }
 
-int CommandObjectExpression::HandleCompletion(CompletionRequest &request) {
+void CommandObjectExpression::HandleCompletion(CompletionRequest &request) {
   EvaluateExpressionOptions options;
   options.SetCoerceToId(m_varobj_options.use_objc);
   options.SetLanguage(m_command_options.language);
@@ -311,7 +311,7 @@ int CommandObjectExpression::HandleCompletion(CompletionRequest &request) {
   // This didn't work, so let's get out before we start doing things that
   // expect a valid frame pointer.
   if (m_interpreter.GetExecutionContext().GetFramePtr() == nullptr)
-    return 0;
+    return;
 
   ExecutionContext exe_ctx(m_interpreter.GetExecutionContext());
 
@@ -321,7 +321,7 @@ int CommandObjectExpression::HandleCompletion(CompletionRequest &request) {
     target = GetDummyTarget();
 
   if (!target)
-    return 0;
+    return;
 
   unsigned cursor_pos = request.GetRawCursorPos();
   llvm::StringRef code = request.GetRawLine();
@@ -341,7 +341,7 @@ int CommandObjectExpression::HandleCompletion(CompletionRequest &request) {
   // exit.
   // FIXME: We should complete the options here.
   if (cursor_pos < raw_start)
-    return 0;
+    return;
 
   // Make the cursor_pos again relative to the start of the code string.
   assert(cursor_pos >= raw_start);
@@ -354,10 +354,9 @@ int CommandObjectExpression::HandleCompletion(CompletionRequest &request) {
       code, llvm::StringRef(), language, UserExpression::eResultTypeAny,
       options, nullptr, error));
   if (error.Fail())
-    return 0;
+    return;
 
   expr->Complete(exe_ctx, request, cursor_pos);
-  return request.GetNumberOfMatches();
 }
 
 static lldb_private::Status
diff --git a/lldb/source/Commands/CommandObjectExpression.h b/lldb/source/Commands/CommandObjectExpression.h
index 89c8e1dbece..8ef76423906 100644
--- a/lldb/source/Commands/CommandObjectExpression.h
+++ b/lldb/source/Commands/CommandObjectExpression.h
@@ -54,7 +54,7 @@ public:
 
   Options *GetOptions() override;
 
-  int HandleCompletion(CompletionRequest &request) override;
+  void HandleCompletion(CompletionRequest &request) override;
 
 protected:
   // IOHandler::Delegate functions
diff --git a/lldb/source/Commands/CommandObjectFrame.cpp b/lldb/source/Commands/CommandObjectFrame.cpp
index 1087c611169..6cbf341d674 100644
--- a/lldb/source/Commands/CommandObjectFrame.cpp
+++ b/lldb/source/Commands/CommandObjectFrame.cpp
@@ -451,14 +451,13 @@ public:
 
   Options *GetOptions() override { return &m_option_group; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     // Arguments are the standard source file completer.
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eVariablePathCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
 protected:
diff --git a/lldb/source/Commands/CommandObjectHelp.cpp b/lldb/source/Commands/CommandObjectHelp.cpp
index 1100ddfe18e..811841fa47a 100644
--- a/lldb/source/Commands/CommandObjectHelp.cpp
+++ b/lldb/source/Commands/CommandObjectHelp.cpp
@@ -201,10 +201,10 @@ bool CommandObjectHelp::DoExecute(Args &command, CommandReturnObject &result) {
   return result.Succeeded();
 }
 
-int CommandObjectHelp::HandleCompletion(CompletionRequest &request) {
+void CommandObjectHelp::HandleCompletion(CompletionRequest &request) {
   // Return the completions of the commands in the help system:
   if (request.GetCursorIndex() == 0) {
-    return m_interpreter.HandleCompletionMatches(request);
+    m_interpreter.HandleCompletionMatches(request);
   } else {
     CommandObject *cmd_obj =
         m_interpreter.GetCommandObject(request.GetParsedLine()[0].ref);
@@ -216,9 +216,9 @@ int CommandObjectHelp::HandleCompletion(CompletionRequest &request) {
     if (cmd_obj) {
       request.GetParsedLine().Shift();
       request.SetCursorIndex(request.GetCursorIndex() - 1);
-      return cmd_obj->HandleCompletion(request);
+      cmd_obj->HandleCompletion(request);
     } else {
-      return m_interpreter.HandleCompletionMatches(request);
+      m_interpreter.HandleCompletionMatches(request);
     }
   }
 }
diff --git a/lldb/source/Commands/CommandObjectHelp.h b/lldb/source/Commands/CommandObjectHelp.h
index a641b19a46d..826cd1e18a8 100644
--- a/lldb/source/Commands/CommandObjectHelp.h
+++ b/lldb/source/Commands/CommandObjectHelp.h
@@ -23,7 +23,7 @@ public:
 
   ~CommandObjectHelp() override;
 
-  int HandleCompletion(CompletionRequest &request) override;
+  void HandleCompletion(CompletionRequest &request) override;
 
   static void GenerateAdditionalHelpAvenuesMessage(
       Stream *s, llvm::StringRef command, llvm::StringRef prefix,
diff --git a/lldb/source/Commands/CommandObjectMultiword.cpp b/lldb/source/Commands/CommandObjectMultiword.cpp
index eeda1fed25c..ecc73a8cbe9 100644
--- a/lldb/source/Commands/CommandObjectMultiword.cpp
+++ b/lldb/source/Commands/CommandObjectMultiword.cpp
@@ -179,11 +179,7 @@ void CommandObjectMultiword::GenerateHelpText(Stream &output_stream) {
                            "'help <command> <subcommand>'.\n");
 }
 
-int CommandObjectMultiword::HandleCompletion(CompletionRequest &request) {
-  // Any of the command matches will provide a complete word, otherwise the
-  // individual completers will override this.
-  request.SetWordComplete(true);
-
+void CommandObjectMultiword::HandleCompletion(CompletionRequest &request) {
   auto arg0 = request.GetParsedLine()[0].ref;
   if (request.GetCursorIndex() == 0) {
     StringList new_matches, descriptions;
@@ -197,23 +193,19 @@ int CommandObjectMultiword::HandleCompletion(CompletionRequest &request) {
       StringList temp_matches;
       CommandObject *cmd_obj = GetSubcommandObject(arg0, &temp_matches);
       if (cmd_obj != nullptr) {
-        if (request.GetParsedLine().GetArgumentCount() == 1) {
-          request.SetWordComplete(true);
-        } else {
+        if (request.GetParsedLine().GetArgumentCount() != 1) {
           request.GetParsedLine().Shift();
           request.SetCursorCharPosition(0);
           request.GetParsedLine().AppendArgument(llvm::StringRef());
-          return cmd_obj->HandleCompletion(request);
+          cmd_obj->HandleCompletion(request);
         }
       }
     }
-    return new_matches.GetSize();
   } else {
     StringList new_matches;
     CommandObject *sub_command_object = GetSubcommandObject(arg0, &new_matches);
     if (sub_command_object == nullptr) {
       request.AddCompletions(new_matches);
-      return request.GetNumberOfMatches();
     } else {
       // Remove the one match that we got from calling GetSubcommandObject.
       new_matches.DeleteStringAtIndex(0);
@@ -360,19 +352,17 @@ Options *CommandObjectProxy::GetOptions() {
   return nullptr;
 }
 
-int CommandObjectProxy::HandleCompletion(CompletionRequest &request) {
+void CommandObjectProxy::HandleCompletion(CompletionRequest &request) {
   CommandObject *proxy_command = GetProxyCommandObject();
   if (proxy_command)
-    return proxy_command->HandleCompletion(request);
-  return 0;
+    proxy_command->HandleCompletion(request);
 }
 
-int CommandObjectProxy::HandleArgumentCompletion(
+void CommandObjectProxy::HandleArgumentCompletion(
     CompletionRequest &request, OptionElementVector &opt_element_vector) {
   CommandObject *proxy_command = GetProxyCommandObject();
   if (proxy_command)
-    return proxy_command->HandleArgumentCompletion(request, opt_element_vector);
-  return 0;
+    proxy_command->HandleArgumentCompletion(request, opt_element_vector);
 }
 
 const char *CommandObjectProxy::GetRepeatCommand(Args &current_command_args,
diff --git a/lldb/source/Commands/CommandObjectPlatform.cpp b/lldb/source/Commands/CommandObjectPlatform.cpp
index 9080ced54ff..4d0b02ad39b 100644
--- a/lldb/source/Commands/CommandObjectPlatform.cpp
+++ b/lldb/source/Commands/CommandObjectPlatform.cpp
@@ -158,10 +158,9 @@ public:
 
   ~CommandObjectPlatformSelect() override = default;
 
-  int HandleCompletion(CompletionRequest &request) override {
+  void HandleCompletion(CompletionRequest &request) override {
     CommandCompletions::PlatformPluginNames(GetCommandInterpreter(), request,
                                             nullptr);
-    return request.GetNumberOfMatches();
   }
 
   Options *GetOptions() override { return &m_option_group; }
diff --git a/lldb/source/Commands/CommandObjectPlugin.cpp b/lldb/source/Commands/CommandObjectPlugin.cpp
index 89e01ba5202..670835c3049 100644
--- a/lldb/source/Commands/CommandObjectPlugin.cpp
+++ b/lldb/source/Commands/CommandObjectPlugin.cpp
@@ -37,13 +37,12 @@ public:
 
   ~CommandObjectPluginLoad() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eDiskFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
 protected:
diff --git a/lldb/source/Commands/CommandObjectProcess.cpp b/lldb/source/Commands/CommandObjectProcess.cpp
index 3d7a59951b5..620be4e5586 100644
--- a/lldb/source/Commands/CommandObjectProcess.cpp
+++ b/lldb/source/Commands/CommandObjectProcess.cpp
@@ -127,14 +127,13 @@ public:
 
   ~CommandObjectProcessLaunch() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
 
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eDiskFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
   Options *GetOptions() override { return &m_options; }
diff --git a/lldb/source/Commands/CommandObjectSettings.cpp b/lldb/source/Commands/CommandObjectSettings.cpp
index 2bdbcd52bc1..b9a7b64f91c 100644
--- a/lldb/source/Commands/CommandObjectSettings.cpp
+++ b/lldb/source/Commands/CommandObjectSettings.cpp
@@ -126,9 +126,9 @@ insert-before or insert-after.");
     bool m_force;
   };
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
 
     const size_t argc = request.GetParsedLine().GetArgumentCount();
     const char *arg = nullptr;
@@ -164,7 +164,6 @@ insert-before or insert-after.");
         }
       }
     }
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -271,13 +270,12 @@ public:
 
   ~CommandObjectSettingsShow() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -527,13 +525,12 @@ public:
 
   ~CommandObjectSettingsList() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -615,14 +612,13 @@ public:
 
   bool WantsCompletion() override { return true; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     if (request.GetCursorIndex() < 2)
       CommandCompletions::InvokeCommonCompletionCallbacks(
           GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
           request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -728,16 +724,14 @@ public:
   // !WantsRawCommandString.
   bool WantsCompletion() override { return true; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     // Attempting to complete variable name
     if (request.GetCursorIndex() < 2)
       CommandCompletions::InvokeCommonCompletionCallbacks(
           GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
           request, nullptr);
-
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -826,16 +820,14 @@ public:
   // !WantsRawCommandString.
   bool WantsCompletion() override { return true; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     // Attempting to complete variable name
     if (request.GetCursorIndex() < 2)
       CommandCompletions::InvokeCommonCompletionCallbacks(
           GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
           request, nullptr);
-
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -929,16 +921,14 @@ public:
   // !WantsRawCommandString.
   bool WantsCompletion() override { return true; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     // Attempting to complete variable name
     if (request.GetCursorIndex() < 2)
       CommandCompletions::InvokeCommonCompletionCallbacks(
           GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
           request, nullptr);
-
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -1021,16 +1011,14 @@ public:
   // !WantsRawCommandString.
   bool WantsCompletion() override { return true; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     // Attempting to complete variable name
     if (request.GetCursorIndex() < 2)
       CommandCompletions::InvokeCommonCompletionCallbacks(
           GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
           request, nullptr);
-
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -1100,16 +1088,14 @@ public:
 
   ~CommandObjectSettingsClear() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     // Attempting to complete variable name
     if (request.GetCursorIndex() < 2)
       CommandCompletions::InvokeCommonCompletionCallbacks(
           GetCommandInterpreter(), CommandCompletions::eSettingsNameCompletion,
           request, nullptr);
-
-    return request.GetNumberOfMatches();
   }
 
 protected:
diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
index b1879c12904..325926373a4 100644
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -258,13 +258,12 @@ public:
 
   Options *GetOptions() override { return &m_option_group; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eDiskFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -1844,13 +1843,12 @@ public:
 
   ~CommandObjectTargetModulesModuleAutoComplete() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eModuleCompletion, request,
         nullptr);
-    return request.GetNumberOfMatches();
   }
 };
 
@@ -1883,13 +1881,12 @@ public:
 
   ~CommandObjectTargetModulesSourceFileAutoComplete() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eSourceFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 };
 
@@ -2534,13 +2531,12 @@ public:
 
   Options *GetOptions() override { return &m_option_group; }
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eDiskFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
 protected:
@@ -4090,13 +4086,12 @@ public:
 
   ~CommandObjectTargetSymbolsAdd() override = default;
 
-  int HandleArgumentCompletion(
-      CompletionRequest &request,
-      OptionElementVector &opt_element_vector) override {
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), CommandCompletions::eDiskFileCompletion,
         request, nullptr);
-    return request.GetNumberOfMatches();
   }
 
   Options *GetOptions() override { return &m_option_group; }
diff --git a/lldb/source/Core/FormatEntity.cpp b/lldb/source/Core/FormatEntity.cpp
index de61c641a56..c90828f4098 100644
--- a/lldb/source/Core/FormatEntity.cpp
+++ b/lldb/source/Core/FormatEntity.cpp
@@ -2346,33 +2346,31 @@ static void AddMatches(const FormatEntity::Entry::Definition *def,
   }
 }
 
-size_t FormatEntity::AutoComplete(CompletionRequest &request) {
+void FormatEntity::AutoComplete(CompletionRequest &request) {
   llvm::StringRef str = request.GetCursorArgumentPrefix();
 
-  request.SetWordComplete(false);
-
   const size_t dollar_pos = str.rfind('$');
   if (dollar_pos == llvm::StringRef::npos)
-    return 0;
+    return;
 
   // Hitting TAB after $ at the end of the string add a "{"
   if (dollar_pos == str.size() - 1) {
     std::string match = str.str();
     match.append("{");
     request.AddCompletion(match);
-    return 1;
+    return;
   }
 
   if (str[dollar_pos + 1] != '{')
-    return 0;
+    return;
 
   const size_t close_pos = str.find('}', dollar_pos + 2);
   if (close_pos != llvm::StringRef::npos)
-    return 0;
+    return;
 
   const size_t format_pos = str.find('%', dollar_pos + 2);
   if (format_pos != llvm::StringRef::npos)
-    return 0;
+    return;
 
   llvm::StringRef partial_variable(str.substr(dollar_pos + 2));
   if (partial_variable.empty()) {
@@ -2380,7 +2378,7 @@ size_t FormatEntity::AutoComplete(CompletionRequest &request) {
     StringList new_matches;
     AddMatches(&g_root, str, llvm::StringRef(), new_matches);
     request.AddCompletions(new_matches);
-    return request.GetNumberOfMatches();
+    return;
   }
 
   // We have a partially specified variable, find it
@@ -2388,7 +2386,7 @@ size_t FormatEntity::AutoComplete(CompletionRequest &request) {
   const FormatEntity::Entry::Definition *entry_def =
       FindEntry(partial_variable, &g_root, remainder);
   if (!entry_def)
-    return 0;
+    return;
 
   const size_t n = entry_def->num_children;
 
@@ -2400,7 +2398,6 @@ size_t FormatEntity::AutoComplete(CompletionRequest &request) {
     } else {
       // "${thread.id" <TAB>
       request.AddCompletion(MakeMatch(str, "}"));
-      request.SetWordComplete(true);
     }
   } else if (remainder.equals(".")) {
     // "${thread." <TAB>
@@ -2414,5 +2411,4 @@ size_t FormatEntity::AutoComplete(CompletionRequest &request) {
     AddMatches(entry_def, str, remainder, new_matches);
     request.AddCompletions(new_matches);
   }
-  return request.GetNumberOfMatches();
 }
diff --git a/lldb/source/Core/IOHandler.cpp b/lldb/source/Core/IOHandler.cpp
index 1a35f300e52..a95e4c17f08 100644
--- a/lldb/source/Core/IOHandler.cpp
+++ b/lldb/source/Core/IOHandler.cpp
@@ -170,15 +170,14 @@ IOHandlerConfirm::IOHandlerConfirm(Debugger &debugger, llvm::StringRef prompt,
 
 IOHandlerConfirm::~IOHandlerConfirm() = default;
 
-int IOHandlerConfirm::IOHandlerComplete(IOHandler &io_handler,
-                                        CompletionRequest &request) {
+void IOHandlerConfirm::IOHandlerComplete(IOHandler &io_handler,
+                                         CompletionRequest &request) {
   if (request.GetRawCursorPos() == 0) {
     if (m_default_response)
       request.AddCompletion("y");
     else
       request.AddCompletion("n");
   }
-  return request.GetNumberOfMatches();
 }
 
 void IOHandlerConfirm::IOHandlerInputComplete(IOHandler &io_handler,
@@ -216,47 +215,20 @@ void IOHandlerConfirm::IOHandlerInputComplete(IOHandler &io_handler,
   }
 }
 
-int IOHandlerDelegate::IOHandlerComplete(IOHandler &io_handler,
-                                         CompletionRequest &request) {
+void IOHandlerDelegate::IOHandlerComplete(IOHandler &io_handler,
+                                          CompletionRequest &request) {
   switch (m_completion) {
   case Completion::None:
     break;
-
   case Completion::LLDBCommand:
-    return io_handler.GetDebugger().GetCommandInterpreter().HandleCompletion(
-        request);
-  case Completion::Expression: {
-    CompletionResult result;
-    CompletionRequest subrequest(request.GetRawLine(),
-                                 request.GetRawCursorPos(), result);
+    io_handler.GetDebugger().GetCommandInterpreter().HandleCompletion(request);
+    break;
+  case Completion::Expression:
     CommandCompletions::InvokeCommonCompletionCallbacks(
         io_handler.GetDebugger().GetCommandInterpreter(),
-        CommandCompletions::eVariablePathCompletion, subrequest, nullptr);
-    StringList matches;
-    StringList descriptions;
-    result.GetMatches(matches);
-    result.GetDescriptions(descriptions);
-
-    size_t num_matches = subrequest.GetNumberOfMatches();
-    if (num_matches > 0) {
-      std::string common_prefix = matches.LongestCommonPrefix();
-      const size_t partial_name_len =
-          subrequest.GetCursorArgumentPrefix().size();
-
-      // If we matched a unique single command, add a space... Only do this if
-      // the completer told us this was a complete word, however...
-      if (num_matches == 1 && subrequest.GetWordComplete()) {
-        common_prefix.push_back(' ');
-      }
-      common_prefix.erase(0, partial_name_len);
-      request.AddCompletion(common_prefix);
-    }
-    request.AddCompletions(matches, descriptions);
-    return request.GetNumberOfMatches();
-  } break;
+        CommandCompletions::eVariablePathCompletion, request, nullptr);
+    break;
   }
-
-  return 0;
 }
 
 IOHandlerEditline::IOHandlerEditline(
@@ -445,13 +417,11 @@ int IOHandlerEditline::FixIndentationCallback(Editline *editline,
       *editline_reader, lines, cursor_position);
 }
 
-int IOHandlerEditline::AutoCompleteCallback(CompletionRequest &request,
-                                            void *baton) {
+void IOHandlerEditline::AutoCompleteCallback(CompletionRequest &request,
+                                             void *baton) {
   IOHandlerEditline *editline_reader = (IOHandlerEditline *)baton;
   if (editline_reader)
-    return editline_reader->m_delegate.IOHandlerComplete(*editline_reader,
-                                                         request);
-  return 0;
+    editline_reader->m_delegate.IOHandlerComplete(*editline_reader, request);
 }
 #endif
 
diff --git a/lldb/source/Core/PluginManager.cpp b/lldb/source/Core/PluginManager.cpp
index 24cadcd85bf..e0026e3d001 100644
--- a/lldb/source/Core/PluginManager.cpp
+++ b/lldb/source/Core/PluginManager.cpp
@@ -1341,10 +1341,10 @@ PluginManager::GetPlatformCreateCallbackForPluginName(ConstString name) {
   return nullptr;
 }
 
-size_t PluginManager::AutoCompletePlatformName(llvm::StringRef name,
-                                               StringList &matches) {
+void PluginManager::AutoCompletePlatformName(llvm::StringRef name,
+                                             CompletionRequest &request) {
   if (name.empty())
-    return matches.GetSize();
+    return;
 
   std::lock_guard<std::recursive_mutex> guard(GetPlatformInstancesMutex());
   PlatformInstances &instances = GetPlatformInstances();
@@ -1354,9 +1354,8 @@ size_t PluginManager::AutoCompletePlatformName(llvm::StringRef name,
   for (pos = instances.begin(); pos != end; ++pos) {
     llvm::StringRef plugin_name(pos->name.GetCString());
     if (plugin_name.startswith(name_sref))
-      matches.AppendString(plugin_name.data());
+      request.AddCompletion(plugin_name.data());
   }
-  return matches.GetSize();
 }
 
 #pragma mark Process
diff --git a/lldb/source/Expression/REPL.cpp b/lldb/source/Expression/REPL.cpp
index d1e7b71e606..01350f3dd74 100644
--- a/lldb/source/Expression/REPL.cpp
+++ b/lldb/source/Expression/REPL.cpp
@@ -433,7 +433,8 @@ void REPL::IOHandlerInputComplete(IOHandler &io_handler, std::string &code) {
   }
 }
 
-int REPL::IOHandlerComplete(IOHandler &io_handler, CompletionRequest &request) {
+void REPL::IOHandlerComplete(IOHandler &io_handler,
+                             CompletionRequest &request) {
   // Complete an LLDB command if the first character is a colon...
   if (request.GetRawLine().startswith(":")) {
     Debugger &debugger = m_target.GetDebugger();
@@ -443,19 +444,19 @@ int REPL::IOHandlerComplete(IOHandler &io_handler, CompletionRequest &request) {
     CompletionResult sub_result;
     CompletionRequest sub_request(new_line, request.GetRawCursorPos() - 1,
                                   sub_result);
-    int result = debugger.GetCommandInterpreter().HandleCompletion(sub_request);
+    debugger.GetCommandInterpreter().HandleCompletion(sub_request);
     StringList matches, descriptions;
     sub_result.GetMatches(matches);
     sub_result.GetDescriptions(descriptions);
     request.AddCompletions(matches, descriptions);
-    return result;
+    return;
   }
 
   // Strip spaces from the line and see if we had only spaces
   if (request.GetRawLineUntilCursor().trim().empty()) {
     // Only spaces on this line, so just indent
     request.AddCompletion(m_indent_str);
-    return 1;
+    return;
   }
 
   std::string current_code;
@@ -482,8 +483,12 @@ int REPL::IOHandlerComplete(IOHandler &io_handler, CompletionRequest &request) {
 
   StringList matches;
   int result = CompleteCode(current_code, matches);
-  request.AddCompletions(matches);
-  return result;
+  if (result == -2) {
+    assert(matches.GetSize() == 1);
+    request.AddCompletion(matches.GetStringAtIndex(0), "",
+                          CompletionMode::RewriteLine);
+  } else
+    request.AddCompletions(matches);
 }
 
 bool QuitCommandOverrideCallback(void *baton, const char **argv) {
diff --git a/lldb/source/Host/common/Editline.cpp b/lldb/source/Host/common/Editline.cpp
index de6560c7af4..a2e8773f8f1 100644
--- a/lldb/source/Host/common/Editline.cpp
+++ b/lldb/source/Host/common/Editline.cpp
@@ -864,26 +864,59 @@ unsigned char Editline::BufferEndCommand(int ch) {
 
 /// Prints completions and their descriptions to the given file. Only the
 /// completions in the interval [start, end) are printed.
-static void PrintCompletion(FILE *output_file, size_t start, size_t end,
-                            StringList &completions, StringList &descriptions) {
-  // This is an 'int' because of printf.
-  int max_len = 0;
-
-  for (size_t i = start; i < end; i++) {
-    const char *completion_str = completions.GetStringAtIndex(i);
-    max_len = std::max((int)strlen(completion_str), max_len);
+static void
+PrintCompletion(FILE *output_file,
+                llvm::ArrayRef<CompletionResult::Completion> results,
+                size_t max_len) {
+  for (const CompletionResult::Completion &c : results) {
+    fprintf(output_file, "\t%-*s", (int)max_len, c.GetCompletion().c_str());
+    if (!c.GetDescription().empty())
+      fprintf(output_file, " -- %s", c.GetDescription().c_str());
+    fprintf(output_file, "\n");
   }
+}
+
+static void
+DisplayCompletions(::EditLine *editline, FILE *output_file,
+                   llvm::ArrayRef<CompletionResult::Completion> results) {
+  assert(!results.empty());
 
-  for (size_t i = start; i < end; i++) {
-    const char *completion_str = completions.GetStringAtIndex(i);
-    const char *description_str = descriptions.GetStringAtIndex(i);
+  fprintf(output_file, "\n" ANSI_CLEAR_BELOW "Available completions:\n");
+  const size_t page_size = 40;
+  bool all = false;
+
+  auto longest =
+      std::max_element(results.begin(), results.end(), [](auto &c1, auto &c2) {
+        return c1.GetCompletion().size() < c2.GetCompletion().size();
+      });
 
-    if (completion_str)
-      fprintf(output_file, "\n\t%-*s", max_len, completion_str);
+  const size_t max_len = longest->GetCompletion().size();
 
-    // Print the description if we got one.
-    if (description_str && strlen(description_str))
-      fprintf(output_file, " -- %s", description_str);
+  if (results.size() < page_size) {
+    PrintCompletion(output_file, results, max_len);
+    return;
+  }
+
+  size_t cur_pos = 0;
+  while (cur_pos < results.size()) {
+    size_t remaining = results.size() - cur_pos;
+    size_t next_size = all ? remaining : std::min(page_size, remaining);
+
+    PrintCompletion(output_file, results.slice(cur_pos, next_size), max_len);
+
+    cur_pos += next_size;
+
+    if (cur_pos >= results.size())
+      break;
+
+    fprintf(output_file, "More (Y/n/a): ");
+    char reply = 'n';
+    int got_char = el_getc(editline, &reply);
+    fprintf(output_file, "\n");
+    if (got_char == -1 || reply == 'n')
+      break;
+    if (reply == 'a')
+      all = true;
   }
 }
 
@@ -892,8 +925,6 @@ unsigned char Editline::TabCommand(int ch) {
     return CC_ERROR;
 
   const LineInfo *line_info = el_line(m_editline);
-  StringList completions, descriptions;
-  int page_size = 40;
 
   llvm::StringRef line(line_info->buffer,
                        line_info->lastchar - line_info->buffer);
@@ -901,71 +932,51 @@ unsigned char Editline::TabCommand(int ch) {
   CompletionResult result;
   CompletionRequest request(line, cursor_index, result);
 
-  const int num_completions =
-      m_completion_callback(request, m_completion_callback_baton);
+  m_completion_callback(request, m_completion_callback_baton);
+
+  llvm::ArrayRef<CompletionResult::Completion> results = result.GetResults();
 
+  StringList completions;
   result.GetMatches(completions);
-  result.GetDescriptions(descriptions);
 
-  if (num_completions == 0)
+  if (results.size() == 0)
     return CC_ERROR;
-  //    if (num_completions == -1)
-  //    {
-  //        el_insertstr (m_editline, m_completion_key);
-  //        return CC_REDISPLAY;
-  //    }
-  //    else
-  if (num_completions == -2) {
-    // Replace the entire line with the first string...
-    el_deletestr(m_editline, line_info->cursor - line_info->buffer);
-    el_insertstr(m_editline, completions.GetStringAtIndex(0));
+
+  if (results.size() == 1) {
+    CompletionResult::Completion completion = results.front();
+    switch (completion.GetMode()) {
+    case CompletionMode::Normal: {
+      std::string to_add = completion.GetCompletion();
+      to_add = to_add.substr(request.GetCursorArgumentPrefix().size());
+      if (request.GetParsedArg().IsQuoted())
+        to_add.push_back(request.GetParsedArg().quote);
+      to_add.push_back(' ');
+      el_insertstr(m_editline, to_add.c_str());
+      break;
+    }
+    case CompletionMode::RewriteLine: {
+      el_deletestr(m_editline, line_info->cursor - line_info->buffer);
+      el_insertstr(m_editline, completion.GetCompletion().c_str());
+      break;
+    }
+    }
     return CC_REDISPLAY;
   }
 
   // If we get a longer match display that first.
-  const char *completion_str = completions.GetStringAtIndex(0);
-  if (completion_str != nullptr && *completion_str != '\0') {
-    el_insertstr(m_editline, completion_str);
+  std::string longest_prefix = completions.LongestCommonPrefix();
+  if (!longest_prefix.empty())
+    longest_prefix =
+        longest_prefix.substr(request.GetCursorArgumentPrefix().size());
+  if (!longest_prefix.empty()) {
+    el_insertstr(m_editline, longest_prefix.c_str());
     return CC_REDISPLAY;
   }
 
-  if (num_completions > 1) {
-    int num_elements = num_completions + 1;
-    fprintf(m_output_file, "\n" ANSI_CLEAR_BELOW "Available completions:");
-    if (num_completions < page_size) {
-      PrintCompletion(m_output_file, 1, num_elements, completions,
-                      descriptions);
-      fprintf(m_output_file, "\n");
-    } else {
-      int cur_pos = 1;
-      char reply;
-      int got_char;
-      while (cur_pos < num_elements) {
-        int endpoint = cur_pos + page_size;
-        if (endpoint > num_elements)
-          endpoint = num_elements;
-
-        PrintCompletion(m_output_file, cur_pos, endpoint, completions,
-                        descriptions);
-        cur_pos = endpoint;
-
-        if (cur_pos >= num_elements) {
-          fprintf(m_output_file, "\n");
-          break;
-        }
-
-        fprintf(m_output_file, "\nMore (Y/n/a): ");
-        reply = 'n';
-        got_char = el_getc(m_editline, &reply);
-        if (got_char == -1 || reply == 'n')
-          break;
-        if (reply == 'a')
-          page_size = num_elements - cur_pos;
-      }
-    }
-    DisplayInput();
-    MoveCursor(CursorLocation::BlockEnd, CursorLocation::EditingCursor);
-  }
+  DisplayCompletions(m_editline, m_output_file, results);
+
+  DisplayInput();
+  MoveCursor(CursorLocation::BlockEnd, CursorLocation::EditingCursor);
   return CC_REDISPLAY;
 }
 
diff --git a/lldb/source/Interpreter/CommandAlias.cpp b/lldb/source/Interpreter/CommandAlias.cpp
index 8c40574ee50..4281ba5338a 100644
--- a/lldb/source/Interpreter/CommandAlias.cpp
+++ b/lldb/source/Interpreter/CommandAlias.cpp
@@ -115,18 +115,16 @@ bool CommandAlias::WantsCompletion() {
   return false;
 }
 
-int CommandAlias::HandleCompletion(CompletionRequest &request) {
+void CommandAlias::HandleCompletion(CompletionRequest &request) {
   if (IsValid())
-    return m_underlying_command_sp->HandleCompletion(request);
-  return -1;
+    m_underlying_command_sp->HandleCompletion(request);
 }
 
-int CommandAlias::HandleArgumentCompletion(
+void CommandAlias::HandleArgumentCompletion(
     CompletionRequest &request, OptionElementVector &opt_element_vector) {
   if (IsValid())
-    return m_underlying_command_sp->HandleArgumentCompletion(
-        request, opt_element_vector);
-  return -1;
+    m_underlying_command_sp->HandleArgumentCompletion(request,
+                                                      opt_element_vector);
 }
 
 Options *CommandAlias::GetOptions() {
diff --git a/lldb/source/Interpreter/CommandInterpreter.cpp b/lldb/source/Interpreter/CommandInterpreter.cpp
index 86cca78241e..dc030d743b2 100644
--- a/lldb/source/Interpreter/CommandInterpreter.cpp
+++ b/lldb/source/Interpreter/CommandInterpreter.cpp
@@ -1754,19 +1754,17 @@ bool CommandInterpreter::HandleCommand(const char *command_line,
   return result.Succeeded();
 }
 
-int CommandInterpreter::HandleCompletionMatches(CompletionRequest &request) {
-  int num_command_matches = 0;
+void CommandInterpreter::HandleCompletionMatches(CompletionRequest &request) {
   bool look_for_subcommand = false;
 
   // For any of the command completions a unique match will be a complete word.
-  request.SetWordComplete(true);
 
   if (request.GetCursorIndex() == -1) {
     // We got nothing on the command line, so return the list of commands
     bool include_aliases = true;
     StringList new_matches, descriptions;
-    num_command_matches = GetCommandNamesMatchingPartialString(
-        "", include_aliases, new_matches, descriptions);
+    GetCommandNamesMatchingPartialString("", include_aliases, new_matches,
+                                         descriptions);
     request.AddCompletions(new_matches, descriptions);
   } else if (request.GetCursorIndex() == 0) {
     // The cursor is in the first argument, so just do a lookup in the
@@ -1776,15 +1774,12 @@ int CommandInterpreter::HandleCompletionMatches(CompletionRequest &request) {
         GetCommandObject(request.GetParsedLine().GetArgumentAtIndex(0),
                          &new_matches, &new_descriptions);
 
-    if (num_command_matches == 1 && cmd_obj && cmd_obj->IsMultiwordObject() &&
+    if (new_matches.GetSize() && cmd_obj && cmd_obj->IsMultiwordObject() &&
         new_matches.GetStringAtIndex(0) != nullptr &&
         strcmp(request.GetParsedLine().GetArgumentAtIndex(0),
                new_matches.GetStringAtIndex(0)) == 0) {
-      if (request.GetParsedLine().GetArgumentCount() == 1) {
-        request.SetWordComplete(true);
-      } else {
+      if (request.GetParsedLine().GetArgumentCount() != 1) {
         look_for_subcommand = true;
-        num_command_matches = 0;
         new_matches.DeleteStringAtIndex(0);
         new_descriptions.DeleteStringAtIndex(0);
         request.GetParsedLine().AppendArgument(llvm::StringRef());
@@ -1793,7 +1788,6 @@ int CommandInterpreter::HandleCompletionMatches(CompletionRequest &request) {
       }
     }
     request.AddCompletions(new_matches, new_descriptions);
-    num_command_matches = request.GetNumberOfMatches();
   }
 
   if (request.GetCursorIndex() > 0 || look_for_subcommand) {
@@ -1802,77 +1796,32 @@ int CommandInterpreter::HandleCompletionMatches(CompletionRequest &request) {
     // matching initial command:
     CommandObject *command_object =
         GetCommandObject(request.GetParsedLine().GetArgumentAtIndex(0));
-    if (command_object == nullptr) {
-      return 0;
-    } else {
+    if (command_object) {
       request.GetParsedLine().Shift();
       request.SetCursorIndex(request.GetCursorIndex() - 1);
-      num_command_matches = command_object->HandleCompletion(request);
+      command_object->HandleCompletion(request);
     }
   }
-
-  return num_command_matches;
 }
 
-int CommandInterpreter::HandleCompletion(CompletionRequest &orig_request) {
-  // Start a new subrequest we can modify.
-  CompletionResult result;
-  CompletionRequest request(orig_request.GetRawLine(),
-                            orig_request.GetRawCursorPos(), result);
+void CommandInterpreter::HandleCompletion(CompletionRequest &request) {
+
   // Don't complete comments, and if the line we are completing is just the
   // history repeat character, substitute the appropriate history line.
-  const char *first_arg = request.GetParsedLine().GetArgumentAtIndex(0);
-  StringList matches, descriptions;
-
-  if (first_arg) {
-    if (first_arg[0] == m_comment_char)
-      return 0;
-    else if (first_arg[0] == CommandHistory::g_repeat_char) {
-      if (auto hist_str = m_command_history.FindString(first_arg)) {
-        matches.InsertStringAtIndex(0, *hist_str);
-        descriptions.InsertStringAtIndex(0, "Previous command history event");
-        return -2;
-      } else
-        return 0;
+  llvm::StringRef first_arg = request.GetParsedLine().GetArgumentAtIndex(0);
+
+  if (!first_arg.empty()) {
+    if (first_arg.front() == m_comment_char)
+      return;
+    if (first_arg.front() == CommandHistory::g_repeat_char) {
+      if (auto hist_str = m_command_history.FindString(first_arg))
+        request.AddCompletion(*hist_str, "Previous command history event",
+                              CompletionMode::RewriteLine);
+      return;
     }
   }
 
-  int num_command_matches = HandleCompletionMatches(request);
-  result.GetMatches(matches);
-  result.GetDescriptions(descriptions);
-
-  if (num_command_matches <= 0)
-    return num_command_matches;
-
-  if (request.GetParsedLine().GetArgumentCount() == 0) {
-    // If we got an empty string, insert nothing.
-    matches.InsertStringAtIndex(0, "");
-    descriptions.InsertStringAtIndex(0, "");
-  } else {
-    // Now figure out if there is a common substring, and if so put that in
-    // element 0, otherwise put an empty string in element 0.
-    std::string command_partial_str = request.GetCursorArgumentPrefix().str();
-
-    std::string common_prefix = matches.LongestCommonPrefix();
-    const size_t partial_name_len = command_partial_str.size();
-    common_prefix.erase(0, partial_name_len);
-
-    // If we matched a unique single command, add a space... Only do this if
-    // the completer told us this was a complete word, however...
-    if (num_command_matches == 1 && request.GetWordComplete()) {
-      char quote_char = request.GetParsedLine()[request.GetCursorIndex()].quote;
-      common_prefix =
-          Args::EscapeLLDBCommandArgument(common_prefix, quote_char);
-      if (quote_char != '\0')
-        common_prefix.push_back(quote_char);
-      common_prefix.push_back(' ');
-    }
-    matches.InsertStringAtIndex(0, common_prefix.c_str());
-    descriptions.InsertStringAtIndex(0, "");
-  }
-  // Add completion to original request.
-  orig_request.AddCompletions(matches, descriptions);
-  return num_command_matches;
+  HandleCompletionMatches(request);
 }
 
 CommandInterpreter::~CommandInterpreter() {}
diff --git a/lldb/source/Interpreter/CommandObject.cpp b/lldb/source/Interpreter/CommandObject.cpp
index fe46b6faf84..eb38971e726 100644
--- a/lldb/source/Interpreter/CommandObject.cpp
+++ b/lldb/source/Interpreter/CommandObject.cpp
@@ -257,14 +257,14 @@ void CommandObject::Cleanup() {
     m_api_locker.unlock();
 }
 
-int CommandObject::HandleCompletion(CompletionRequest &request) {
+void CommandObject::HandleCompletion(CompletionRequest &request) {
   // Default implementation of WantsCompletion() is !WantsRawCommandString().
   // Subclasses who want raw command string but desire, for example, argument
   // completion should override WantsCompletion() to return true, instead.
   if (WantsRawCommandString() && !WantsCompletion()) {
     // FIXME: Abstract telling the completion to insert the completion
     // character.
-    return -1;
+    return;
   } else {
     // Can we do anything generic with the options?
     Options *cur_options = GetOptions();
@@ -278,11 +278,11 @@ int CommandObject::HandleCompletion(CompletionRequest &request) {
       bool handled_by_options = cur_options->HandleOptionCompletion(
           request, opt_element_vector, GetCommandInterpreter());
       if (handled_by_options)
-        return request.GetNumberOfMatches();
+        return;
     }
 
     // If we got here, the last word is not an option or an option argument.
-    return HandleArgumentCompletion(request, opt_element_vector);
+    HandleArgumentCompletion(request, opt_element_vector);
   }
 }
 
diff --git a/lldb/source/Interpreter/CommandObjectRegexCommand.cpp b/lldb/source/Interpreter/CommandObjectRegexCommand.cpp
index 94e52a36fb3..693d18ce7bd 100644
--- a/lldb/source/Interpreter/CommandObjectRegexCommand.cpp
+++ b/lldb/source/Interpreter/CommandObjectRegexCommand.cpp
@@ -84,13 +84,9 @@ bool CommandObjectRegexCommand::AddRegexCommand(const char *re_cstr,
   return false;
 }
 
-int CommandObjectRegexCommand::HandleCompletion(CompletionRequest &request) {
+void CommandObjectRegexCommand::HandleCompletion(CompletionRequest &request) {
   if (m_completion_type_mask) {
     CommandCompletions::InvokeCommonCompletionCallbacks(
         GetCommandInterpreter(), m_completion_type_mask, request, nullptr);
-    return request.GetNumberOfMatches();
-  } else {
-    request.SetWordComplete(false);
   }
-  return 0;
 }
diff --git a/lldb/source/Interpreter/OptionValue.cpp b/lldb/source/Interpreter/OptionValue.cpp
index 00c8642595b..bc929aa9dab 100644
--- a/lldb/source/Interpreter/OptionValue.cpp
+++ b/lldb/source/Interpreter/OptionValue.cpp
@@ -565,11 +565,8 @@ bool OptionValue::DumpQualifiedName(Stream &strm) const {
   return dumped_something;
 }
 
-size_t OptionValue::AutoComplete(CommandInterpreter &interpreter,
-                                 CompletionRequest &request) {
-  request.SetWordComplete(false);
-  return request.GetNumberOfMatches();
-}
+void OptionValue::AutoComplete(CommandInterpreter &interpreter,
+                               CompletionRequest &request) {}
 
 Status OptionValue::SetValueFromString(llvm::StringRef value,
                                        VarSetOperationType op) {
diff --git a/lldb/source/Interpreter/OptionValueArch.cpp b/lldb/source/Interpreter/OptionValueArch.cpp
index 92dc45d092b..7271c1471f9 100644
--- a/lldb/source/Interpreter/OptionValueArch.cpp
+++ b/lldb/source/Interpreter/OptionValueArch.cpp
@@ -68,11 +68,9 @@ lldb::OptionValueSP OptionValueArch::DeepCopy() const {
   return OptionValueSP(new OptionValueArch(*this));
 }
 
-size_t OptionValueArch::AutoComplete(CommandInterpreter &interpreter,
-                                     CompletionRequest &request) {
-  request.SetWordComplete(false);
+void OptionValueArch::AutoComplete(CommandInterpreter &interpreter,
+                                   CompletionRequest &request) {
   CommandCompletions::InvokeCommonCompletionCallbacks(
       interpreter, CommandCompletions::eArchitectureCompletion, request,
       nullptr);
-  return request.GetNumberOfMatches();
 }
diff --git a/lldb/source/Interpreter/OptionValueBoolean.cpp b/lldb/source/Interpreter/OptionValueBoolean.cpp
index 8be8220fb30..bfc7760e207 100644
--- a/lldb/source/Interpreter/OptionValueBoolean.cpp
+++ b/lldb/source/Interpreter/OptionValueBoolean.cpp
@@ -71,9 +71,8 @@ lldb::OptionValueSP OptionValueBoolean::DeepCopy() const {
   return OptionValueSP(new OptionValueBoolean(*this));
 }
 
-size_t OptionValueBoolean::AutoComplete(CommandInterpreter &interpreter,
-                                        CompletionRequest &request) {
-  request.SetWordComplete(false);
+void OptionValueBoolean::AutoComplete(CommandInterpreter &interpreter,
+                                      CompletionRequest &request) {
   static const llvm::StringRef g_autocomplete_entries[] = {
       "true", "false", "on", "off", "yes", "no", "1", "0"};
 
@@ -87,5 +86,4 @@ size_t OptionValueBoolean::AutoComplete(CommandInterpreter &interpreter,
     if (entry.startswith_lower(request.GetCursorArgumentPrefix()))
       request.AddCompletion(entry);
   }
-  return request.GetNumberOfMatches();
 }
diff --git a/lldb/source/Interpreter/OptionValueEnumeration.cpp b/lldb/source/Interpreter/OptionValueEnumeration.cpp
index 0b76bd0601a..3df0e27bab4 100644
--- a/lldb/source/Interpreter/OptionValueEnumeration.cpp
+++ b/lldb/source/Interpreter/OptionValueEnumeration.cpp
@@ -102,10 +102,8 @@ lldb::OptionValueSP OptionValueEnumeration::DeepCopy() const {
   return OptionValueSP(new OptionValueEnumeration(*this));
 }
 
-size_t OptionValueEnumeration::AutoComplete(CommandInterpreter &interpreter,
-                                            CompletionRequest &request) {
-  request.SetWordComplete(false);
-
+void OptionValueEnumeration::AutoComplete(CommandInterpreter &interpreter,
+                                          CompletionRequest &request) {
   const uint32_t num_enumerators = m_enumerations.GetSize();
   if (!request.GetCursorArgumentPrefix().empty()) {
     for (size_t i = 0; i < num_enumerators; ++i) {
@@ -118,5 +116,4 @@ size_t OptionValueEnumeration::AutoComplete(CommandInterpreter &interpreter,
     for (size_t i = 0; i < num_enumerators; ++i)
       request.AddCompletion(m_enumerations.GetCStringAtIndex(i).GetStringRef());
   }
-  return request.GetNumberOfMatches();
 }
diff --git a/lldb/source/Interpreter/OptionValueFileSpec.cpp b/lldb/source/Interpreter/OptionValueFileSpec.cpp
index 062d7ccdf2a..20d3d4e68e3 100644
--- a/lldb/source/Interpreter/OptionValueFileSpec.cpp
+++ b/lldb/source/Interpreter/OptionValueFileSpec.cpp
@@ -99,12 +99,10 @@ lldb::OptionValueSP OptionValueFileSpec::DeepCopy() const {
   return OptionValueSP(new OptionValueFileSpec(*this));
 }
 
-size_t OptionValueFileSpec::AutoComplete(CommandInterpreter &interpreter,
-                                         CompletionRequest &request) {
-  request.SetWordComplete(false);
+void OptionValueFileSpec::AutoComplete(CommandInterpreter &interpreter,
+                                       CompletionRequest &request) {
   CommandCompletions::InvokeCommonCompletionCallbacks(
       interpreter, m_completion_mask, request, nullptr);
-  return request.GetNumberOfMatches();
 }
 
 const lldb::DataBufferSP &OptionValueFileSpec::GetFileContents() {
diff --git a/lldb/source/Interpreter/OptionValueFormatEntity.cpp b/lldb/source/Interpreter/OptionValueFormatEntity.cpp
index 1bb8c9f6955..8dc52650a33 100644
--- a/lldb/source/Interpreter/OptionValueFormatEntity.cpp
+++ b/lldb/source/Interpreter/OptionValueFormatEntity.cpp
@@ -116,7 +116,7 @@ lldb::OptionValueSP OptionValueFormatEntity::DeepCopy() const {
   return OptionValueSP(new OptionValueFormatEntity(*this));
 }
 
-size_t OptionValueFormatEntity::AutoComplete(CommandInterpreter &interpreter,
-                                             CompletionRequest &request) {
-  return FormatEntity::AutoComplete(request);
+void OptionValueFormatEntity::AutoComplete(CommandInterpreter &interpreter,
+                                           CompletionRequest &request) {
+  FormatEntity::AutoComplete(request);
 }
diff --git a/lldb/source/Interpreter/OptionValueUUID.cpp b/lldb/source/Interpreter/OptionValueUUID.cpp
index f39b66b77bb..d2226ff3743 100644
--- a/lldb/source/Interpreter/OptionValueUUID.cpp
+++ b/lldb/source/Interpreter/OptionValueUUID.cpp
@@ -62,9 +62,8 @@ lldb::OptionValueSP OptionValueUUID::DeepCopy() const {
   return OptionValueSP(new OptionValueUUID(*this));
 }
 
-size_t OptionValueUUID::AutoComplete(CommandInterpreter &interpreter,
-                                     CompletionRequest &request) {
-  request.SetWordComplete(false);
+void OptionValueUUID::AutoComplete(CommandInterpreter &interpreter,
+                                   CompletionRequest &request) {
   ExecutionContext exe_ctx(interpreter.GetExecutionContext());
   Target *target = exe_ctx.GetTargetPtr();
   if (target) {
@@ -87,5 +86,4 @@ size_t OptionValueUUID::AutoComplete(CommandInterpreter &interpreter,
       }
     }
   }
-  return request.GetNumberOfMatches();
 }
diff --git a/lldb/source/Interpreter/Options.cpp b/lldb/source/Interpreter/Options.cpp
index ba15c020f2d..536cbaae5f2 100644
--- a/lldb/source/Interpreter/Options.cpp
+++ b/lldb/source/Interpreter/Options.cpp
@@ -645,8 +645,6 @@ bool Options::VerifyPartialOptions(CommandReturnObject &result) {
 bool Options::HandleOptionCompletion(CompletionRequest &request,
                                      OptionElementVector &opt_element_vector,
                                      CommandInterpreter &interpreter) {
-  request.SetWordComplete(true);
-
   // For now we just scan the completions to see if the cursor position is in
   // an option or its argument.  Otherwise we'll call HandleArgumentCompletion.
   // In the future we can use completion to validate options as well if we
@@ -739,7 +737,6 @@ bool Options::HandleOptionCompletion(CompletionRequest &request,
       if (opt_defs_index != -1) {
         HandleOptionArgumentCompletion(subrequest, opt_element_vector, i,
                                        interpreter);
-        request.SetWordComplete(subrequest.GetWordComplete());
         return true;
       } else {
         // No completion callback means no completions...
diff --git a/lldb/source/Symbol/Variable.cpp b/lldb/source/Symbol/Variable.cpp
index 72025fc0e3b..3ec97b1fce7 100644
--- a/lldb/source/Symbol/Variable.cpp
+++ b/lldb/source/Symbol/Variable.cpp
@@ -583,7 +583,6 @@ static void PrivateAutoComplete(
       case eTypeClassTypedef:
       case eTypeClassVector: {
         request.AddCompletion(prefix_path.str());
-        request.SetWordComplete(true);
       } break;
 
       case eTypeClassClass:
@@ -603,7 +602,6 @@ static void PrivateAutoComplete(
           request.AddCompletion((prefix_path + "->").str());
         else {
           request.AddCompletion(prefix_path.str());
-          request.SetWordComplete(true);
         }
       } break;
       }
@@ -749,12 +747,10 @@ static void PrivateAutoComplete(
   }
 }
 
-size_t Variable::AutoComplete(const ExecutionContext &exe_ctx,
-                              CompletionRequest &request) {
+void Variable::AutoComplete(const ExecutionContext &exe_ctx,
+                            CompletionRequest &request) {
   CompilerType compiler_type;
 
   PrivateAutoComplete(exe_ctx.GetFramePtr(), request.GetCursorArgumentPrefix(),
                       "", compiler_type, request);
-
-  return request.GetNumberOfMatches();
 }
diff --git a/lldb/source/Utility/ArchSpec.cpp b/lldb/source/Utility/ArchSpec.cpp
index 18e70e7ca07..fc2d43925a3 100644
--- a/lldb/source/Utility/ArchSpec.cpp
+++ b/lldb/source/Utility/ArchSpec.cpp
@@ -243,7 +243,7 @@ void ArchSpec::ListSupportedArchNames(StringList &list) {
     list.AppendString(g_core_definitions[i].name);
 }
 
-size_t ArchSpec::AutoComplete(CompletionRequest &request) {
+void ArchSpec::AutoComplete(CompletionRequest &request) {
   if (!request.GetCursorArgumentPrefix().empty()) {
     for (uint32_t i = 0; i < llvm::array_lengthof(g_core_definitions); ++i) {
       if (NameMatches(g_core_definitions[i].name, NameMatch::StartsWith,
@@ -255,7 +255,6 @@ size_t ArchSpec::AutoComplete(CompletionRequest &request) {
     ListSupportedArchNames(matches);
     request.AddCompletions(matches);
   }
-  return request.GetNumberOfMatches();
 }
 
 #define CPU_ANY (UINT32_MAX)
diff --git a/lldb/source/Utility/CompletionRequest.cpp b/lldb/source/Utility/CompletionRequest.cpp
index 6a8ab160c41..7fd5260f7d5 100644
--- a/lldb/source/Utility/CompletionRequest.cpp
+++ b/lldb/source/Utility/CompletionRequest.cpp
@@ -64,13 +64,16 @@ std::string CompletionResult::Completion::GetUniqueKey() const {
   std::string result;
   result.append(std::to_string(m_completion.size()));
   result.append(m_completion);
+  result.append(std::to_string(static_cast<int>(m_mode)));
+  result.append(":");
   result.append(m_descripton);
   return result;
 }
 
 void CompletionResult::AddResult(llvm::StringRef completion,
-                                 llvm::StringRef description) {
-  Completion r(completion, description);
+                                 llvm::StringRef description,
+                                 CompletionMode mode) {
+  Completion r(completion, description, mode);
 
   // Add the completion if we haven't seen the same value before.
   if (m_added_values.insert(r.GetUniqueKey()).second)
@@ -80,11 +83,11 @@ void CompletionResult::AddResult(llvm::StringRef completion,
 void CompletionResult::GetMatches(StringList &matches) const {
   matches.Clear();
   for (const Completion &completion : m_results)
-    matches.AppendString(completion.m_completion);
+    matches.AppendString(completion.GetCompletion());
 }
 
 void CompletionResult::GetDescriptions(StringList &descriptions) const {
   descriptions.Clear();
   for (const Completion &completion : m_results)
-    descriptions.AppendString(completion.m_descripton);
+    descriptions.AppendString(completion.GetDescription());
 }