[clang-format] Fix putting ObjC message arguments in one line for multiline receiver

[jolesiak]

Summary

Currently BreakBeforeParameter is set to true everytime message receiver spans multiple lines, e.g.:

[[object block:^{
  return 42;
}] aa:42 bb:42];

will be formatted:

[[object block:^{
  return 42;
}] aa:42
   bb:42];

even though arguments could fit into one line. This change fixes this behavior.

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

lib/Format/ContinuationIndenter.cpp

unsigned ContinuationIndenter::moveStateToNextToken(LineState &State,
   }
   if (!Current.opensScope() && !Current.closesScope() &&
       !Current.is(TT_PointerOrReference))
     State.LowestLevelOnLine =
         std::min(State.LowestLevelOnLine, Current.NestingLevel);
   if (Current.isMemberAccess())
     State.Stack.back().StartOfFunctionCall =
         !Current.NextOperator ? 0 : State.Column;
-  if (Current.is(TT_SelectorName))
+  if (Current.is(TT_SelectorName) &&
+      !State.Stack.back().ObjCSelectorNameFound) {
     State.Stack.back().ObjCSelectorNameFound = true;
+
+    // Reevaluate whether ObjC message arguments fit into one line.
+    // If a receiver spans multiple lines, e.g.:
+    //   [[object block:^{
+    //     return 42;
+    //   }] a:42 b:42];
+    // BreakBeforeParameter is calculated based on an incorrect assumption
+    // (it is checked whether the whole expression fits into one line without
+    // considering a line break inside a message receiver).
+    if (Current.Previous && Current.Previous->closesScope() &&
+        Current.Previous->MatchingParen &&
+        Current.Previous->MatchingParen->Previous) {
+      const FormatToken &CurrentScopeOpener =
+          *Current.Previous->MatchingParen->Previous;
+      if (CurrentScopeOpener.is(TT_ObjCMethodExpr) &&
+          CurrentScopeOpener.MatchingParen) {
+        int NecessarySpaceInLine =
+            getLengthToMatchingParen(CurrentScopeOpener, State.Stack) +
+            CurrentScopeOpener.TotalLength - Current.TotalLength - 1;
+        if (State.Column + Current.ColumnWidth + NecessarySpaceInLine <=
+            Style.ColumnLimit)
+          State.Stack.back().BreakBeforeParameter = false;
+      }
+    }
+  }
   if (Current.is(TT_CtorInitializerColon) &&
       Style.BreakConstructorInitializers != FormatStyle::BCIS_AfterColon) {
     // Indent 2 from the column, so:
     // SomeClass::SomeClass()
     //     : First(...), ...
     //       Next(...)
     //       ^ line up here.
     State.Stack.back().Indent =

unittests/Format/FormatTestObjC.cpp

verifyFormat("[object\n"
                "    firstBlock:^{\n"
                "      a = 42;\n"
                "    }\n"
                "    notBlock:42\n"
                "    secondBlock:^{\n"
                "      a = 42;\n"
                "    }];");
 
+  // Message receiver taking multiple lines.
+  Style.ColumnLimit = 20;
+  // Non-corner case.
+  verifyFormat("[[object block:^{\n"
+               "  return 42;\n"
+               "}] a:42 b:42];");
+  // Arguments just fit into one line.
+  verifyFormat("[[object block:^{\n"
+               "  return 42;\n"
+               "}] aaaaaaa:42 b:42];");
+  // Arguments just over a column limit.
+  verifyFormat("[[object block:^{\n"
+               "  return 42;\n"
+               "}] aaaaaaa:42\n"
+               "        bb:42];");
+  // Non-corner case.
+  verifyFormat("[[object aaa:42\n"
+               "           b:42]\n"
+               "    cc:42 d:42];");
+  // Arguments just fit into one line.
+  verifyFormat("[[object aaa:42\n"
+               "           b:42]\n"
+               "    cccccc:42 d:42];");
+  // Arguments just over a column limit.
+  verifyFormat("[[object aaa:42\n"
+               "           b:42]\n"
+               "    cccccc:42\n"
+               "        dd:42];");
+
   Style.ColumnLimit = 70;
   verifyFormat(
       "void f() {\n"
       "  popup_wdow_.reset([[RenderWidgetPopupWindow alloc]\n"
       "      iniithContentRect:NSMakRet(origin_global.x, origin_global.y,\n"
       "                                 pos.width(), pos.height())\n"
       "                syeMask:NSBorderlessWindowMask\n"
       "                  bking:NSBackingStoreBuffered\n"