[clang-format/ObjC] Prohibit breaking after a bracket opening ObjC method expression

[jolesiak]

Summary

Don't break after a "[" opening ObjC method expression.
Tests are added in D48719 where formatting is improved (to avoid adding and changing tests immediately).

[benhamilton]

Can you add a test, please?

[jolesiak]

In D48718#1146805, @benhamilton wrote:

Can you add a test, please?

The test could look like:

aaaaa = [a aa:aa
           aa:aa];

with appropriate column limit.
Right now, however, this would be formatted:

aaaaa =
    [a aa:aa aa:aa];

This behavior is improved in D48719. To avoid adding

aaaaa =
    [a aa:aa aa:aa];

test in this change and changing it to:

aaaaa = [a aa:aa
           aa:aa];

in D48719 I decided to omit it altogether in this change.

Sorry for the confusion. If you prefer me to add this test and modify in later commit I'll do it.

[benhamilton]

Sorry for the confusion. If you prefer me to add this test and modify in later commit I'll do it.

I see. Just mentioning what you did in the diff description is probably OK.

lib/Format/ContinuationIndenter.cpp

bool ContinuationIndenter::canBreak(const LineState &State) {
   }
 
   // If binary operators are moved to the next line (including commas for some
   // styles of constructor initializers), that's always ok.
   if (!Current.isOneOf(TT_BinaryOperator, tok::comma) &&
       State.Stack.back().NoLineBreakInOperand)
     return false;
 
+  if (Previous.is(tok::l_square) && Previous.is(TT_ObjCMethodExpr))
+    return false;
+
   return !State.Stack.back().NoLineBreak;
 }
 
 bool ContinuationIndenter::mustBreak(const LineState &State) {
   const FormatToken &Current = *State.NextToken;
   const FormatToken &Previous = *Current.Previous;
   if (Current.MustBreakBefore || Current.is(TT_InlineASMColon))
     return true;