clang-format: Do not binpack initialization lists

Summary:
This patch tries to avoid binpacking when initializing lists/arrays, to allow things like:

  static int types[] = {
      registerType1(),
      registerType2(),
      registerType3(),
  };
  std::map<int, std::string> x = {
      { 0, "foo fjakfjaklf kljj" },
      { 1, "bar fjakfjaklf kljj" },
      { 2, "stuff fjakfjaklf kljj" },
  };

This is similar to how dictionnaries are formatted, and actually corresponds to the same conditions: when initializing a container (and not just 'calling' a constructor).

Such formatting involves 2 things:
* Line breaks around the content of the block. This can be forced by adding a comma or comment after the last element
* Elements should not be binpacked

This patch considers the block is an initializer list if it either ends with a comma, or follows an assignment, which seems to provide a sensible approximation.

Reviewers: krasimir, djasper

Reviewed By: djasper

Subscribers: malcolm.parsons, klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D34238

llvm-svn: 306868

clang/lib/Format/ContinuationIndenter.cpp

@@ -1063,12 +1063,12 @@ void ContinuationIndenter::moveStatePastScopeOpener(LineState &State,
                        Current.MatchingParen->Previous &&
                        Current.MatchingParen->Previous->is(tok::comma);
     AvoidBinPacking =
-        (Current.is(TT_ArrayInitializerLSquare) && EndsInComma) ||
-        Current.is(TT_DictLiteral) ||
+        EndsInComma || Current.is(TT_DictLiteral) ||
         Style.Language == FormatStyle::LK_Proto || !Style.BinPackArguments ||
         (NextNoComment &&
          NextNoComment->isOneOf(TT_DesignatedInitializerPeriod,
                                 TT_DesignatedInitializerLSquare));
+    BreakBeforeParameter = EndsInComma;
     if (Current.ParameterCount > 1)
       NestedBlockIndent = std::max(NestedBlockIndent, State.Column + 1);
   } else {

clang/unittests/Format/FormatTest.cpp

@@ -6004,7 +6004,10 @@ TEST_F(FormatTest, LayoutBraceInitializersInReturnStatement) {
 TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
   verifyFormat("vector<int> x{1, 2, 3, 4};");
   verifyFormat("vector<int> x{\n"
-               "    1, 2, 3, 4,\n"
+               "    1,\n"
+               "    2,\n"
+               "    3,\n"
+               "    4,\n"
                "};");
   verifyFormat("vector<T> x{{}, {}, {}, {}};");
   verifyFormat("f({1, 2});");
@@ -6049,6 +6052,17 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
                "};");
   verifyFormat("#define A {a, a},");
 
+  // Binpacking only if there is no trailing comma
+  verifyFormat("const Aaaaaa aaaaa = {aaaaaaaaaa, bbbbbbbbbb,\n"
+               "                      cccccccccc, dddddddddd};",
+			   getLLVMStyleWithColumns(50));
+  verifyFormat("const Aaaaaa aaaaa = {\n"
+               "    aaaaaaaaaaa,\n"
+               "    bbbbbbbbbbb,\n"
+               "    ccccccccccc,\n"
+               "    ddddddddddd,\n"
+               "};", getLLVMStyleWithColumns(50));
+
   // Cases where distinguising braced lists and blocks is hard.
   verifyFormat("vector<int> v{12} GUARDED_BY(mutex);");
   verifyFormat("void f() {\n"
@@ -6128,10 +6142,12 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
                    "                           // Second element:\n"
                    "                           2};",
                    getLLVMStyleWithColumns(30)));
-  // A trailing comma should still lead to an enforced line break.
+  // A trailing comma should still lead to an enforced line break and no
+  // binpacking.
   EXPECT_EQ("vector<int> SomeVector = {\n"
             "    // aaa\n"
-            "    1, 2,\n"
+            "    1,\n"
+            "    2,\n"
             "};",
             format("vector<int> SomeVector = { // aaa\n"
                    "    1, 2, };"));
@@ -6297,7 +6313,7 @@ TEST_F(FormatTest, FormatsBracedListsInColumnLayout) {
       "     aaaaaaaaaaaa, a, aaaaaaaaaa, aaaaaaaaa, aaa}};");
 
   // No column layout should be used here.
-  verifyFormat("aaaaaaaaaaaaaaa = {aaaaaaaaaaaaaaaaaaaaaaaaaaa, 0, 0,\n"
+  verifyFormat("aaaaaaaaaaaaaaa = {aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, 0, 0,\n"
                "                   bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb};");
 
   verifyNoCrash("a<,");

clang/unittests/Format/FormatTestJava.cpp

@@ -237,7 +237,10 @@ TEST_F(FormatTestJava, EnumDeclarations) {
 TEST_F(FormatTestJava, ArrayInitializers) {
   verifyFormat("new int[] {1, 2, 3, 4};");
   verifyFormat("new int[] {\n"
-               "    1, 2, 3, 4,\n"
+               "    1,\n"
+               "    2,\n"
+               "    3,\n"
+               "    4,\n"
                "};");
 
   FormatStyle Style = getStyleWithColumns(65);