[clang-format/ObjC] Improve split priorities for ObjC methods

Reduce penalty for aligning ObjC method arguments using the colon alignment as
this is the canonical way.

Trying to fit a whole expression into one line should not force other line
breaks (e.g. when ObjC method expression is a part of other expression).

llvm-svn: 336520

clang/lib/Format/FormatToken.h

@@ -248,6 +248,11 @@ struct FormatToken {
   /// selector consist of.
   unsigned ObjCSelectorNameParts = 0;
 
+  /// The 0-based index of the parameter/argument. For ObjC it is set
+  /// for the selector name token.
+  /// For now calculated only for ObjC.
+  unsigned ParameterIndex = 0;
+
   /// Stores the number of required fake parentheses and the
   /// corresponding operator precedence.
   ///

clang/lib/Format/TokenAnnotator.cpp

@@ -725,6 +725,8 @@ private:
                    Contexts.back().LongestObjCSelectorName)
             Contexts.back().LongestObjCSelectorName =
                 Tok->Previous->ColumnWidth;
+          Tok->Previous->ParameterIndex =
+              Contexts.back().FirstObjCSelectorName->ObjCSelectorNameParts;
           ++Contexts.back().FirstObjCSelectorName->ObjCSelectorNameParts;
         }
       } else if (Contexts.back().ColonIsForRangeExpr) {
@@ -2142,8 +2144,20 @@ void TokenAnnotator::calculateFormattingInformation(AnnotatedLine &Line) {
     // FIXME: Only calculate this if CanBreakBefore is true once static
     // initializers etc. are sorted out.
     // FIXME: Move magic numbers to a better place.
-    Current->SplitPenalty = 20 * Current->BindingStrength +
-                            splitPenalty(Line, *Current, InFunctionDecl);
+
+    // Reduce penalty for aligning ObjC method arguments using the colon
+    // alignment as this is the canonical way (still prefer fitting everything
+    // into one line if possible). Trying to fit a whole expression into one
+    // line should not force other line breaks (e.g. when ObjC method
+    // expression is a part of other expression).
+    Current->SplitPenalty = splitPenalty(Line, *Current, InFunctionDecl);
+    if (Style.Language == FormatStyle::LK_ObjC &&
+        Current->is(TT_SelectorName) && Current->ParameterIndex > 0) {
+      if (Current->ParameterIndex == 1)
+        Current->SplitPenalty += 5 * Current->BindingStrength;
+    } else {
+      Current->SplitPenalty += 20 * Current->BindingStrength;
+    }
 
     Current = Current->Next;
   }

clang/unittests/Format/FormatTestObjC.cpp

@@ -678,6 +678,18 @@ TEST_F(FormatTestObjC, FormatObjCMethodExpr) {
   verifyFormat("[(id)foo bar:(id) ? baz : quux];");
   verifyFormat("4 > 4 ? (id)a : (id)baz;");
 
+  unsigned PreviousColumnLimit = Style.ColumnLimit;
+  Style.ColumnLimit = 50;
+  // Instead of:
+  // bool a =
+  //     ([object a:42] == 0 || [object a:42
+  //                                    b:42] == 0);
+  verifyFormat("bool a = ([object a:42] == 0 ||\n"
+               "          [object a:42 b:42] == 0);");
+  Style.ColumnLimit = PreviousColumnLimit;
+  verifyFormat("bool a = ([aaaaaaaa aaaaa] == aaaaaaaaaaaaaaaaa ||\n"
+               "          [aaaaaaaa aaaaa] == aaaaaaaaaaaaaaaaaaaa);");
+
   // This tests that the formatter doesn't break after "backing" but before ":",
   // which would be at 80 columns.
   verifyFormat(
@@ -754,11 +766,10 @@ TEST_F(FormatTestObjC, FormatObjCMethodExpr) {
       "[self aaaaaaaaaaaaa:aaaaaaaaaaaaaaa, aaaaaaaaaaaaaaa, aaaaaaaaaaaaaaa,\n"
       "                    aaaaaaaaaaaaaaa, aaaaaaaaaaaaaaa, aaaaaaaaaaaaaaa,\n"
       "                    aaaaaaaaaaaaaaa, aaaaaaaaaaaaaaa];");
+
   verifyFormat("[self // break\n"
                "      a:a\n"
                "    aaa:aaa];");
-  verifyFormat("bool a = ([aaaaaaaa aaaaa] == aaaaaaaaaaaaaaaaa ||\n"
-               "          [aaaaaaaa aaaaa] == aaaaaaaaaaaaaaaaaaaa);");
 
   // Formats pair-parameters.
   verifyFormat("[I drawRectOn:surface ofSize:aa:bbb atOrigin:cc:dd];");
@@ -803,6 +814,12 @@ TEST_F(FormatTestObjC, FormatObjCMethodExpr) {
   verifyFormat("[((Foo *)foo) bar];");
   verifyFormat("[((Foo *)foo) bar:1 blech:2];");
 
+  Style.ColumnLimit = 20;
+  verifyFormat("aaaaa = [a aa:aa\n"
+               "           aa:aa];");
+  verifyFormat("aaaaaa = [aa aa:aa\n"
+               "             aa:aa];");
+
   Style.ColumnLimit = 70;
   verifyFormat(
       "void f() {\n"