[clang-format] Do not break after ObjC category open paren

Summary:
Previously, `clang-format` would break Objective-C
category extensions after the opening parenthesis to avoid
breaking the protocol list:

```
% echo "@interface ccccccccccccc (ccccccccccc) <ccccccccccccc> { }" | \
  clang-format -assume-filename=foo.h -style="{BasedOnStyle: llvm, \
  ColumnLimit: 40}"
@interface ccccccccccccc (
    ccccccccccc) <ccccccccccccc> {
}
```

This looks fairly odd, as we could have kept the category extension
on the previous line.

Category extensions are a single item, so they are generally very
short compared to protocol lists. We should prefer breaking after the
opening `<` of the protocol list over breaking after the opening `(`
of the category extension.

With this diff, we now avoid breaking after the category extension's
open paren, which causes us to break after the protocol list's
open angle bracket:

```
% echo "@interface ccccccccccccc (ccccccccccc) <ccccccccccccc> { }" | \
  ./bin/clang-format -assume-filename=foo.h -style="{BasedOnStyle: llvm, \
  ColumnLimit: 40}"
@interface ccccccccccccc (ccccccccccc) <
    ccccccccccccc> {
}
```

Test Plan: New test added. Confirmed test failed before diff and
  passed after diff by running:
  % make -j16 FormatTests && ./tools/clang/unittests/Format/FormatTests

Reviewers: djasper, jolesiak

Reviewed By: djasper

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D45526

llvm-svn: 329919

clang/lib/Format/TokenAnnotator.cpp

@@ -2272,6 +2272,13 @@ unsigned TokenAnnotator::splitPenalty(const AnnotatedLine &Line,
   if (Left.is(tok::colon) && Left.is(TT_ObjCMethodExpr))
     return Line.MightBeFunctionDecl ? 50 : 500;
 
+  // In Objective-C type declarations, avoid breaking after the category's
+  // open paren (we'll prefer breaking after the protocol list's opening
+  // angle bracket, if present).
+  if (Line.Type == LT_ObjCDecl && Left.is(tok::l_paren) && Left.Previous &&
+      Left.Previous->isOneOf(tok::identifier, tok::greater))
+    return 500;
+
   if (Left.is(tok::l_paren) && InFunctionDecl &&
       Style.AlignAfterOpenBracket != FormatStyle::BAS_DontAlign)
     return 100;

clang/unittests/Format/FormatTestObjC.cpp

@@ -334,6 +334,9 @@ TEST_F(FormatTestObjC, FormatObjCInterface) {
                "    ccccccccccccc, ccccccccccccc,\n"
                "    ccccccccccccc, ccccccccccccc> {\n"
                "}");
+  verifyFormat("@interface ccccccccccccc (ccccccccccc) <\n"
+               "    ccccccccccccc> {\n"
+               "}");
   Style.ObjCBinPackProtocolList = FormatStyle::BPS_Never;
   verifyFormat("@interface ddddddddddddd () <\n"
                "    ddddddddddddd,\n"