clang-format: Several improvements around formatting braced lists.

In particular:
* If the difference between the longest and shortest element, we copped
  out of column format completely. Now, we instead allow to arrange
  these in a single column, essentially enforcing a one-per-line format.
* Allow column layout even if there are braced lists. Especially, if
  there are many short lists, this can be beneficial. The bad case,
  where there is a long nested init list is usually caught as we now
  limit the length difference of the longest and shortest element.

llvm-svn: 236851

2 files changed, 33 insertions, 10 deletions

diff --git a/clang/lib/Format/FormatToken.cpp b/clang/lib/Format/FormatToken.cpp
index 0addbfed0ce..cc1ef55fa4f 100644
--- a/clang/lib/Format/FormatToken.cpp
+++ b/clang/lib/Format/FormatToken.cpp
@@ -199,13 +199,14 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
   // create a column layout. If it has a nested list, column layout ensures one
   // list element per line. If the difference between the shortest and longest
   // element is too large, column layout would create too much whitespace.
-  if (HasNestedBracedList || Commas.size() < 5 || Token->NestingLevel != 0 ||
-      MaxItemLength - MinItemLength > 10)
+  if (Commas.size() < 5 || Token->NestingLevel != 0)
     return;
 
   // We can never place more than ColumnLimit / 3 items in a row (because of the
   // spaces and the comma).
-  for (unsigned Columns = 1; Columns <= Style.ColumnLimit / 3; ++Columns) {
+  unsigned MaxColumns =
+      MaxItemLength - MinItemLength > 10 ? 1 : Style.ColumnLimit / 3;
+  for (unsigned Columns = 1; Columns <= MaxColumns; ++Columns) {
     ColumnFormat Format;
     Format.Columns = Columns;
     Format.ColumnSizes.resize(Columns);
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 0995bb162a0..9d29a268485 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -6223,9 +6223,18 @@ TEST_F(FormatTest, LayoutCxx11BraceInitializers) {
       ExtraSpaces);
   verifyFormat(
       "std::vector<MyValues> aaaaaaaaaaaaaaaaaaa{\n"
-      "    aaaaaaa, aaaaaaaaaa, aaaaa, aaaaaaaaaaaaaaa, aaa, aaaaaaaaaa, a,\n"
-      "    aaaaaaaaaaaaaaaaaaaaa, aaaaaaaaaaaa,\n"
-      "    aaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaa, aaaaaaa, a};");
+      "    aaaaaaa,\n"
+      "    aaaaaaaaaa,\n"
+      "    aaaaa,\n"
+      "    aaaaaaaaaaaaaaa,\n"
+      "    aaa,\n"
+      "    aaaaaaaaaa,\n"
+      "    a,\n"
+      "    aaaaaaaaaaaaaaaaaaaaa,\n"
+      "    aaaaaaaaaaaa,\n"
+      "    aaaaaaaaaaaaaaaaaaa + aaaaaaaaaaaaaaaaaaa,\n"
+      "    aaaaaaa,\n"
+      "    a};");
   verifyFormat("vector<int> foo = { ::SomeGlobalFunction() };", ExtraSpaces);
 }
 
@@ -6263,6 +6272,19 @@ TEST_F(FormatTest, FormatsBracedListsInColumnLayout) {
   verifyFormat("vector<int> aaaaaaaaaaaaaaaaaaaaaa = {\n"
                "    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};",
                getLLVMStyleWithColumns(43));
+  verifyFormat(
+      "static unsigned SomeValues[10][3] = {\n"
+      "    {1, 4, 0},  {4, 9, 0},  {4, 5, 9},  {8, 5, 4}, {1, 8, 4},\n"
+      "    {10, 1, 6}, {11, 0, 9}, {2, 11, 9}, {5, 2, 9}, {11, 2, 7}};");
+  verifyFormat("static auto fields = new vector<string>{\n"
+               "    \"aaaaaaaaaaaaa\",\n"
+               "    \"aaaaaaaaaaaaa\",\n"
+               "    \"aaaaaaaaaaaa\",\n"
+               "    \"aaaaaaaaaaaaaa\",\n"
+               "    \"aaaaaaaaaaaaaaaaaaaaaaaaa\",\n"
+               "    \"aaaaaaaaaaaa\",\n"
+               "    \"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\",\n"
+               "};");
 
   // Trailing commas.
   verifyFormat("vector<int> x = {\n"
@@ -6277,15 +6299,15 @@ TEST_F(FormatTest, FormatsBracedListsInColumnLayout) {
                "                 1, 1, 1, 1,\n"
                "                 /**/ /**/};",
                getLLVMStyleWithColumns(39));
+
+  // With nested lists, we should either format one item per line or all nested
+  // lists one on line.
+  // FIXME: For some nested lists, we can do better.
   verifyFormat("return {{aaaaaaaaaaaaaaaaaaaaa},\n"
                "        {aaaaaaaaaaaaaaaaaaa},\n"
                "        {aaaaaaaaaaaaaaaaaaaaa},\n"
                "        {aaaaaaaaaaaaaaaaa}};",
                getLLVMStyleWithColumns(60));
-
-  // With nested lists, we should either format one item per line or all nested
-  // lists one one line.
-  // FIXME: For some nested lists, we can do better.
   verifyFormat(
       "SomeStruct my_struct_array = {\n"
       "    {aaaaaa, aaaaaaaa, aaaaaaaaaa, aaaaaaaaa, aaaaaaaaa, aaaaaaaaaa,\n"