[clang-format] Add support of consecutive declarations alignment

This allows clang-format to align identifiers in consecutive
declarations. This is useful for increasing the readability of the code
in the same way the alignment of assignations is.

The code is a slightly modified version of the consecutive assignment
alignment code. Currently only the identifiers are aligned, and there is
no support of alignment of the pointer star or reference symbol.

The patch also solve the issue of alignments not being possible due to
the ColumnLimit for both the existing AlignConsecutiveAligments and the
new AlignConsecutiveDeclarations.

Patch by Beren Minor, thank you.

Review: http://reviews.llvm.org/D12362
llvm-svn: 248999

3 files changed, 146 insertions, 11 deletions

diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index aa227a1f00a..d8a15e4cdfb 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -201,6 +201,8 @@ template <> struct MappingTraits<FormatStyle> {
     IO.mapOptional("AlignAfterOpenBracket", Style.AlignAfterOpenBracket);
     IO.mapOptional("AlignConsecutiveAssignments",
                    Style.AlignConsecutiveAssignments);
+    IO.mapOptional("AlignConsecutiveDeclarations",
+                   Style.AlignConsecutiveDeclarations);
     IO.mapOptional("AlignEscapedNewlinesLeft", Style.AlignEscapedNewlinesLeft);
     IO.mapOptional("AlignOperands", Style.AlignOperands);
     IO.mapOptional("AlignTrailingComments", Style.AlignTrailingComments);
@@ -416,6 +418,7 @@ FormatStyle getLLVMStyle() {
   LLVMStyle.AlignOperands = true;
   LLVMStyle.AlignTrailingComments = true;
   LLVMStyle.AlignConsecutiveAssignments = false;
+  LLVMStyle.AlignConsecutiveDeclarations = false;
   LLVMStyle.AllowAllParametersOfDeclarationOnNextLine = true;
   LLVMStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_All;
   LLVMStyle.AllowShortBlocksOnASingleLine = false;
diff --git a/clang/lib/Format/WhitespaceManager.cpp b/clang/lib/Format/WhitespaceManager.cpp
index 3d6040e90cd..18d73b553e6 100644
--- a/clang/lib/Format/WhitespaceManager.cpp
+++ b/clang/lib/Format/WhitespaceManager.cpp
@@ -29,13 +29,15 @@ WhitespaceManager::Change::Change(
     bool CreateReplacement, const SourceRange &OriginalWhitespaceRange,
     unsigned IndentLevel, int Spaces, unsigned StartOfTokenColumn,
     unsigned NewlinesBefore, StringRef PreviousLinePostfix,
-    StringRef CurrentLinePrefix, tok::TokenKind Kind, bool ContinuesPPDirective)
+    StringRef CurrentLinePrefix, tok::TokenKind Kind, bool ContinuesPPDirective,
+    bool IsStartOfDeclName)
     : CreateReplacement(CreateReplacement),
       OriginalWhitespaceRange(OriginalWhitespaceRange),
       StartOfTokenColumn(StartOfTokenColumn), NewlinesBefore(NewlinesBefore),
       PreviousLinePostfix(PreviousLinePostfix),
       CurrentLinePrefix(CurrentLinePrefix), Kind(Kind),
-      ContinuesPPDirective(ContinuesPPDirective), IndentLevel(IndentLevel),
+      ContinuesPPDirective(ContinuesPPDirective),
+      IsStartOfDeclName(IsStartOfDeclName), IndentLevel(IndentLevel),
       Spaces(Spaces), IsTrailingComment(false), TokenLength(0),
       PreviousEndOfTokenColumn(0), EscapedNewlineColumn(0),
       StartOfBlockComment(nullptr), IndentationOffset(0) {}
@@ -52,19 +54,21 @@ void WhitespaceManager::replaceWhitespace(FormatToken &Tok, unsigned Newlines,
   if (Tok.Finalized)
     return;
   Tok.Decision = (Newlines > 0) ? FD_Break : FD_Continue;
-  Changes.push_back(Change(true, Tok.WhitespaceRange, IndentLevel, Spaces,
-                           StartOfTokenColumn, Newlines, "", "",
-                           Tok.Tok.getKind(), InPPDirective && !Tok.IsFirst));
+  Changes.push_back(
+      Change(true, Tok.WhitespaceRange, IndentLevel, Spaces, StartOfTokenColumn,
+             Newlines, "", "", Tok.Tok.getKind(), InPPDirective && !Tok.IsFirst,
+             Tok.is(TT_StartOfName) || Tok.is(TT_FunctionDeclarationName)));
 }
 
 void WhitespaceManager::addUntouchableToken(const FormatToken &Tok,
                                             bool InPPDirective) {
   if (Tok.Finalized)
     return;
-  Changes.push_back(Change(false, Tok.WhitespaceRange, /*IndentLevel=*/0,
-                           /*Spaces=*/0, Tok.OriginalColumn, Tok.NewlinesBefore,
-                           "", "", Tok.Tok.getKind(),
-                           InPPDirective && !Tok.IsFirst));
+  Changes.push_back(
+      Change(false, Tok.WhitespaceRange, /*IndentLevel=*/0,
+             /*Spaces=*/0, Tok.OriginalColumn, Tok.NewlinesBefore, "", "",
+             Tok.Tok.getKind(), InPPDirective && !Tok.IsFirst,
+             Tok.is(TT_StartOfName) || Tok.is(TT_FunctionDeclarationName)));
 }
 
 void WhitespaceManager::replaceWhitespaceInToken(
@@ -84,7 +88,8 @@ void WhitespaceManager::replaceWhitespaceInToken(
       // calculate the new length of the comment and to calculate the changes
       // for which to do the alignment when aligning comments.
       Tok.is(TT_LineComment) && Newlines > 0 ? tok::comment : tok::unknown,
-      InPPDirective && !Tok.IsFirst));
+      InPPDirective && !Tok.IsFirst,
+      Tok.is(TT_StartOfName) || Tok.is(TT_FunctionDeclarationName)));
 }
 
 const tooling::Replacements &WhitespaceManager::generateReplacements() {
@@ -93,6 +98,7 @@ const tooling::Replacements &WhitespaceManager::generateReplacements() {
 
   std::sort(Changes.begin(), Changes.end(), Change::IsBeforeInFile(SourceMgr));
   calculateLineBreakInformation();
+  alignConsecutiveDeclarations();
   alignConsecutiveAssignments();
   alignTrailingComments();
   alignEscapedNewlines();
@@ -152,6 +158,7 @@ void WhitespaceManager::alignConsecutiveAssignments() {
     return;
 
   unsigned MinColumn = 0;
+  unsigned MaxColumn = UINT_MAX;
   unsigned StartOfSequence = 0;
   unsigned EndOfSequence = 0;
   bool FoundAssignmentOnLine = false;
@@ -168,6 +175,7 @@ void WhitespaceManager::alignConsecutiveAssignments() {
     if (StartOfSequence > 0 && StartOfSequence < EndOfSequence)
       alignConsecutiveAssignments(StartOfSequence, EndOfSequence, MinColumn);
     MinColumn = 0;
+    MaxColumn = UINT_MAX;
     StartOfSequence = 0;
     EndOfSequence = 0;
   };
@@ -207,7 +215,18 @@ void WhitespaceManager::alignConsecutiveAssignments() {
         StartOfSequence = i;
 
       unsigned ChangeMinColumn = Changes[i].StartOfTokenColumn;
+      int LineLengthAfter = -Changes[i].Spaces;
+      for (unsigned j = i; j != e && Changes[j].NewlinesBefore == 0; ++j)
+        LineLengthAfter += Changes[j].Spaces + Changes[j].TokenLength;
+      unsigned ChangeMaxColumn = Style.ColumnLimit - LineLengthAfter;
+
+      if (ChangeMinColumn > MaxColumn || ChangeMaxColumn < MinColumn) {
+        AlignSequence();
+        StartOfSequence = i;
+      }
+
       MinColumn = std::max(MinColumn, ChangeMinColumn);
+      MaxColumn = std::min(MaxColumn, ChangeMaxColumn);
     }
   }
 
@@ -242,6 +261,110 @@ void WhitespaceManager::alignConsecutiveAssignments(unsigned Start,
   }
 }
 
+// Walk through all of the changes and find sequences of declaration names to
+// align.  To do so, keep track of the lines and whether or not a name was found
+// on align. If a name is found on a line, extend the current sequence. If the
+// current line cannot be part of a sequence, e.g. because there is an empty
+// line before it or it contains non-declarations, finalize the previous
+// sequence.
+void WhitespaceManager::alignConsecutiveDeclarations() {
+  if (!Style.AlignConsecutiveDeclarations)
+    return;
+
+  unsigned MinColumn = 0;
+  unsigned MaxColumn = UINT_MAX;
+  unsigned StartOfSequence = 0;
+  unsigned EndOfSequence = 0;
+  bool FoundDeclarationOnLine = false;
+  bool FoundLeftBraceOnLine = false;
+  bool FoundLeftParenOnLine = false;
+
+  auto AlignSequence = [&] {
+    if (StartOfSequence > 0 && StartOfSequence < EndOfSequence)
+      alignConsecutiveDeclarations(StartOfSequence, EndOfSequence, MinColumn);
+    MinColumn = 0;
+    MaxColumn = UINT_MAX;
+    StartOfSequence = 0;
+    EndOfSequence = 0;
+  };
+
+  for (unsigned i = 0, e = Changes.size(); i != e; ++i) {
+    if (Changes[i].NewlinesBefore != 0) {
+      EndOfSequence = i;
+      if (Changes[i].NewlinesBefore > 1 || !FoundDeclarationOnLine ||
+          FoundLeftBraceOnLine || FoundLeftParenOnLine)
+        AlignSequence();
+      FoundDeclarationOnLine = false;
+      FoundLeftBraceOnLine = false;
+      FoundLeftParenOnLine = false;
+    }
+
+    if (Changes[i].Kind == tok::r_brace) {
+      if (!FoundLeftBraceOnLine)
+        AlignSequence();
+      FoundLeftBraceOnLine = false;
+    } else if (Changes[i].Kind == tok::l_brace) {
+      FoundLeftBraceOnLine = true;
+      if (!FoundDeclarationOnLine)
+        AlignSequence();
+    } else if (Changes[i].Kind == tok::r_paren) {
+      if (!FoundLeftParenOnLine)
+        AlignSequence();
+      FoundLeftParenOnLine = false;
+    } else if (Changes[i].Kind == tok::l_paren) {
+      FoundLeftParenOnLine = true;
+      if (!FoundDeclarationOnLine)
+        AlignSequence();
+    } else if (!FoundDeclarationOnLine && !FoundLeftBraceOnLine &&
+               !FoundLeftParenOnLine && Changes[i].IsStartOfDeclName) {
+      FoundDeclarationOnLine = true;
+      if (StartOfSequence == 0)
+        StartOfSequence = i;
+
+      unsigned ChangeMinColumn = Changes[i].StartOfTokenColumn;
+      int LineLengthAfter = -Changes[i].Spaces;
+      for (unsigned j = i; j != e && Changes[j].NewlinesBefore == 0; ++j)
+        LineLengthAfter += Changes[j].Spaces + Changes[j].TokenLength;
+      unsigned ChangeMaxColumn = Style.ColumnLimit - LineLengthAfter;
+
+      if (ChangeMinColumn > MaxColumn || ChangeMaxColumn < MinColumn) {
+        AlignSequence();
+        StartOfSequence = i;
+      }
+
+      MinColumn = std::max(MinColumn, ChangeMinColumn);
+      MaxColumn = std::min(MaxColumn, ChangeMaxColumn);
+    }
+  }
+
+  EndOfSequence = Changes.size();
+  AlignSequence();
+}
+
+void WhitespaceManager::alignConsecutiveDeclarations(unsigned Start,
+                                                     unsigned End,
+                                                     unsigned Column) {
+  bool FoundDeclarationOnLine = false;
+  int Shift = 0;
+  for (unsigned i = Start; i != End; ++i) {
+    if (Changes[i].NewlinesBefore != 0) {
+      FoundDeclarationOnLine = false;
+      Shift = 0;
+    }
+
+    if (!FoundDeclarationOnLine && Changes[i].IsStartOfDeclName) {
+      FoundDeclarationOnLine = true;
+      Shift = Column - Changes[i].StartOfTokenColumn;
+      Changes[i].Spaces += Shift;
+    }
+
+    assert(Shift >= 0);
+    Changes[i].StartOfTokenColumn += Shift;
+    if (i + 1 != Changes.size())
+      Changes[i + 1].PreviousEndOfTokenColumn += Shift;
+  }
+}
+
 void WhitespaceManager::alignTrailingComments() {
   unsigned MinColumn = 0;
   unsigned MaxColumn = UINT_MAX;
diff --git a/clang/lib/Format/WhitespaceManager.h b/clang/lib/Format/WhitespaceManager.h
index d9738383298..8e03c6d3fc7 100644
--- a/clang/lib/Format/WhitespaceManager.h
+++ b/clang/lib/Format/WhitespaceManager.h
@@ -110,7 +110,7 @@ private:
            unsigned IndentLevel, int Spaces, unsigned StartOfTokenColumn,
            unsigned NewlinesBefore, StringRef PreviousLinePostfix,
            StringRef CurrentLinePrefix, tok::TokenKind Kind,
-           bool ContinuesPPDirective);
+           bool ContinuesPPDirective, bool IsStartOfDeclName);
 
     bool CreateReplacement;
     // Changes might be in the middle of a token, so we cannot just keep the
@@ -126,6 +126,7 @@ private:
     // the \c BreakableToken is still doing its own alignment.
     tok::TokenKind Kind;
     bool ContinuesPPDirective;
+    bool IsStartOfDeclName;
 
     // The number of nested blocks the token is in. This is used to add tabs
     // only for the indentation, and not for alignment, when
@@ -173,6 +174,14 @@ private:
   void alignConsecutiveAssignments(unsigned Start, unsigned End,
                                    unsigned Column);
 
+  /// \brief Align consecutive declarations over all \c Changes.
+  void alignConsecutiveDeclarations();
+
+  /// \brief Align consecutive declarations from change \p Start to change \p
+  /// End at the specified \p Column.
+  void alignConsecutiveDeclarations(unsigned Start, unsigned End,
+                                    unsigned Column);
+
   /// \brief Align trailing comments over all \c Changes.
   void alignTrailingComments();