[clang-format] Do not break Objective-C string literals inside array literals

Summary:
Concatenating Objective-C string literals inside an array literal
raises the warning -Wobjc-string-concatenation (which is enabled by default).

clang-format currently splits and concatenates string literals like
the following:

  NSArray *myArray = @[ @"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ];

into:

  NSArray *myArray =
        @[ @"aaaaaaaaaaaaaaaaaaaaaaaaaaaa"
           @"aaaaaaaaa" ];

which raises the warning. This is https://bugs.llvm.org/show_bug.cgi?id=36153 .

The options I can think of to fix this are:

1) Have clang-format disable Wobjc-string-concatenation by emitting
pragmas around the formatted code
2) Have clang-format wrap the string literals in a macro (which
disables the warning)
3) Disable string splitting for Objective-C string literals inside
array literals

I think 1) has no precedent, and I couldn't find a good
identity() macro for 2). So, this diff implements 3).

Test Plan: make -j12 FormatTests && ./tools/clang/unittests/Format/FormatTests

Reviewers: jolesiak, stephanemoore, djasper

Reviewed By: jolesiak

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D42704

llvm-svn: 324618

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Format/ContinuationIndenter.h b/clang/lib/Format/ContinuationIndenter.h
index bb2b7320fd4..64b3a3eba9f 100644
--- a/clang/lib/Format/ContinuationIndenter.h
+++ b/clang/lib/Format/ContinuationIndenter.h
@@ -208,7 +208,8 @@ struct ParenState {
         NoLineBreakInOperand(false), LastOperatorWrapped(true),
         ContainsLineBreak(false), ContainsUnwrappedBuilder(false),
         AlignColons(true), ObjCSelectorNameFound(false),
-        HasMultipleNestedBlocks(false), NestedBlockInlined(false) {}
+        HasMultipleNestedBlocks(false), NestedBlockInlined(false),
+        IsInsideObjCArrayLiteral(false) {}
 
   /// \brief The position to which a specific parenthesis level needs to be
   /// indented.
@@ -318,6 +319,10 @@ struct ParenState {
   /// "function" in JavaScript) is not wrapped to a new line.
   bool NestedBlockInlined : 1;
 
+  /// \brief \c true if the current \c ParenState represents an Objective-C
+  /// array literal.
+  bool IsInsideObjCArrayLiteral : 1;
+
   bool operator<(const ParenState &Other) const {
     if (Indent != Other.Indent)
       return Indent < Other.Indent;