[clang-format] Do not emit replacements while regrouping if Cpp includes are OK

Summary:
Currently clang-format would always emit a replacement for multi-block #include
sections if `IBS_Regroup`, even if the sections are correct:
```
% cat ~/test.h
#include <a.h>

#include "b.h"
% bin/clang-format --output-replacements-xml -style=google ~/test.h
<?xml version='1.0'?>
<replacements xml:space='preserve' incomplete_format='false'>
<replacement offset='0' length='30'>#include &lt;a.h>&#10;&#10;#include "b.h"</replacement>
</replacements>
%
```

This change makes clang-format not emit replacements in this case.
The logic is similar to the one implemented for Java in r354452.

Reviewers: ioeric

Reviewed By: ioeric

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D60199

llvm-svn: 357599

1 files changed, 16 insertions, 4 deletions

diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
index 4dee599fe01..49977b6eff8 100644
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -1753,6 +1753,7 @@ FindCursorIndex(const SmallVectorImpl<IncludeDirective> &Includes,
 static void sortCppIncludes(const FormatStyle &Style,
                             const SmallVectorImpl<IncludeDirective> &Includes,
                             ArrayRef<tooling::Range> Ranges, StringRef FileName,
+                            StringRef Code,
                             tooling::Replacements &Replaces, unsigned *Cursor) {
   unsigned IncludesBeginOffset = Includes.front().Offset;
   unsigned IncludesEndOffset =
@@ -1788,6 +1789,10 @@ static void sortCppIncludes(const FormatStyle &Style,
 
   // If the #includes are out of order, we generate a single replacement fixing
   // the entire block. Otherwise, no replacement is generated.
+  // In case Style.IncldueStyle.IncludeBlocks != IBS_Preserve, this check is not
+  // enough as additional newlines might be added or removed across #include
+  // blocks. This we handle below by generating the updated #imclude blocks and
+  // comparing it to the original.
   if (Indices.size() == Includes.size() &&
       std::is_sorted(Indices.begin(), Indices.end()) &&
       Style.IncludeStyle.IncludeBlocks == tooling::IncludeStyle::IBS_Preserve)
@@ -1808,6 +1813,11 @@ static void sortCppIncludes(const FormatStyle &Style,
     CurrentCategory = Includes[Index].Category;
   }
 
+  // If the #includes are out of order, we generate a single replacement fixing
+  // the entire range of blocks. Otherwise, no replacement is generated.
+  if (result == Code.substr(IncludesBeginOffset, IncludesBlockSize))
+    return;
+
   auto Err = Replaces.add(tooling::Replacement(
       FileName, Includes.front().Offset, IncludesBlockSize, result));
   // FIXME: better error handling. For now, just skip the replacement for the
@@ -1876,8 +1886,8 @@ tooling::Replacements sortCppIncludes(const FormatStyle &Style, StringRef Code,
           MainIncludeFound = true;
         IncludesInBlock.push_back({IncludeName, Line, Prev, Category});
       } else if (!IncludesInBlock.empty() && !EmptyLineSkipped) {
-        sortCppIncludes(Style, IncludesInBlock, Ranges, FileName, Replaces,
-                        Cursor);
+        sortCppIncludes(Style, IncludesInBlock, Ranges, FileName, Code,
+                        Replaces, Cursor);
         IncludesInBlock.clear();
         FirstIncludeBlock = false;
       }
@@ -1887,8 +1897,10 @@ tooling::Replacements sortCppIncludes(const FormatStyle &Style, StringRef Code,
       break;
     SearchFrom = Pos + 1;
   }
-  if (!IncludesInBlock.empty())
-    sortCppIncludes(Style, IncludesInBlock, Ranges, FileName, Replaces, Cursor);
+  if (!IncludesInBlock.empty()) {
+    sortCppIncludes(Style, IncludesInBlock, Ranges, FileName, Code, Replaces,
+                    Cursor);
+  }
   return Replaces;
 }