clang-format: fix formatting of ObjC @synchronized blocks

[Typz]

Summary

The blocks used to be formatted using the "default" behavior, and would
thus be mistaken for function calls followed by blocks: this could lead
to unexpected inlining of the block and extra line-break before the
opening brace.

They are now formatted similarly to @autoreleasepool blocks, as
expected:

@synchronized(self) {
    f();
}

[Typz]

lib/Format/UnwrappedLineParser.cpp

1130

Wondering if formatting with this style is appropriate: the clang-format doc points in that direction, but it seems to me both @synchronized and @autoreleasepool are more akin to "control statements".

For consistency (esp. in ObjC++ code), as a user, I would tend to have these blocks indented like control statements while interfaces/implementations blocks would be indented like classes/structs.

So maybe it would be better to introduce a new BraceWrapping style 'AfterObjCSpecialBlock` to control these cases, matching the possibilities that are given for control statements vs classes. What do you think?

[benhamilton]

lib/Format/UnwrappedLineParser.cpp

1130

Hmm, I definitely agree with that logic. I don't see them acting as declarations in any way, they are definitely like control statements.

[Typz]

lib/Format/UnwrappedLineParser.cpp

1130

Ok, i can change this. Two questions though:

• Should I do this in this patch, or a separate patch? (won't be a big change in any case, but it can still be seen as 2 separate issues/changes)
• Should I introduce a new BraceWrapping flag (AfterObjCSpecialBlock), or simply apply AfterControlStatement to these blocks?

[benhamilton]

lib/Format/UnwrappedLineParser.cpp

1130

Personally, I feel AfterControlStatement applies to these. I'm not an expert on this, though, so I will defer to others on the review.

[Typz]

lib/Format/UnwrappedLineParser.cpp

1130

I created another diff to change the field that is used to control brace wrapping after these blocks: https://reviews.llvm.org/D43232

This patch here should now only relate to the parsing of @synchronized blocks.

[benhamilton]

Just a question on the test.

unittests/Format/FormatTestObjC.cpp

193–198

Why is the block repeated twice?

200–207

Same question.

[Typz]

unittests/Format/FormatTestObjC.cpp

193–198

not sure why, I just copied the @autoreleasepool test code.
this may be to detect some more 'internal' error, which would lead to any visible effect on the first statement itself...

lib/Format/UnwrappedLineParser.cpp

case tok::at:
         nextToken();
         if (FormatTok->Tok.is(tok::l_brace)) {
           if (Style.BraceWrapping.AfterObjCDeclaration)
             addUnwrappedLine();
           parseBlock(/*MustBeDeclaration=*/false);
         }
         addUnwrappedLine();
         return;
+      case tok::objc_synchronized:
+        nextToken();
+        if (FormatTok->Tok.is(tok::l_paren))
+           // Skip synchronization object
+           parseParens();
+        if (FormatTok->Tok.is(tok::l_brace)) {
+          if (Style.BraceWrapping.AfterObjCDeclaration)
+            addUnwrappedLine();
+          parseBlock(/*MustBeDeclaration=*/false);
+        }
+        addUnwrappedLine();
+        return;
       case tok::objc_try:
         // This branch isn't strictly necessary (the kw_try case below would
         // do this too after the tok::at is parsed above).  But be explicit.
         parseTryCatch();
         return;
       default:
         break;
       }

unittests/Format/FormatTestObjC.cpp

verifyFormat("@autoreleasepool\n"
                "  f();\n"
                "}\n"
                "@autoreleasepool\n"
                "{\n"
                "  f();\n"
                "}\n");
 }
 
+TEST_F(FormatTestObjC, FormatObjCSynchronized) {
+  verifyFormat("@synchronized(self) {\n"
+               "  f();\n"
+               "}\n"
+               "@synchronized(self) {\n"
+               "  f();\n"
+               "}\n");
+  Style.BreakBeforeBraces = FormatStyle::BS_Allman;
+  verifyFormat("@synchronized(self)\n"
+               "{\n"
+               "  f();\n"
+               "}\n"
+               "@synchronized(self)\n"
+               "{\n"
+               "  f();\n"
+               "}\n");
+}
+
 TEST_F(FormatTestObjC, FormatObjCInterface) {
   verifyFormat("@interface Foo : NSObject <NSSomeDelegate> {\n"
                "@public\n"
                "  int field1;\n"
                "@protected\n"
                "  int field2;\n"
                "@private\n"
                "  int field3;\n"