clang-format: Be more conservative about column layout formatting.

Specifically, if a braced list has at least one nested braced list,
format it either all on one line or in one column (i.e. one item per
line).

This seems in general to be an improvement as the structure of nested
braced lists can make a tightly packed outer braced list hard to read.

llvm-svn: 193345

2 files changed, 17 insertions, 7 deletions

diff --git a/clang/lib/Format/FormatToken.cpp b/clang/lib/Format/FormatToken.cpp
index 4ca4edbe158..8ac704a3bb6 100644
--- a/clang/lib/Format/FormatToken.cpp
+++ b/clang/lib/Format/FormatToken.cpp
@@ -99,12 +99,15 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
   // trailing comments which are otherwise ignored for column alignment.
   SmallVector<unsigned, 8> EndOfLineItemLength;
 
+  bool HasNestedBracedList = false;
   for (unsigned i = 0, e = Commas.size() + 1; i != e; ++i) {
     // Skip comments on their own line.
     while (ItemBegin->HasUnescapedNewline && ItemBegin->isTrailingComment())
       ItemBegin = ItemBegin->Next;
 
     MustBreakBeforeItem.push_back(ItemBegin->MustBreakBefore);
+    if (ItemBegin->is(tok::l_brace))
+      HasNestedBracedList = true;
     const FormatToken *ItemEnd = NULL;
     if (i == Commas.size()) {
       ItemEnd = Token->MatchingParen;
@@ -142,7 +145,7 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
     ColumnFormat Format;
     Format.Columns = Columns;
     Format.ColumnSizes.resize(Columns);
-    Format.LineCount = 0;
+    Format.LineCount = 1;
     bool HasRowWithSufficientColumns = false;
     unsigned Column = 0;
     for (unsigned i = 0, e = ItemLengths.size(); i != e; ++i) {
@@ -172,6 +175,11 @@ void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
     if (Format.TotalWidth > Style.ColumnLimit)
       continue;
 
+    // If this braced list has nested braced list, we format it either with one
+    // element per line or with all elements on one line.
+    if (HasNestedBracedList && Columns > 1 && Format.LineCount > 1)
+      continue;
+
     Formats.push_back(Format);
   }
 }
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index f6e42ca211d..9b24f040d16 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -1864,14 +1864,14 @@ TEST_F(FormatTest, NestedStaticInitializers) {
       "      333333333333333333333333333333}},\n"
       "    {{1, 2, 3}}, {{1, 2, 3}}};");
 
-  // FIXME: We might at some point want to handle this similar to parameter
-  // lists, where we have an option to put each on a single line.
   verifyFormat(
       "struct {\n"
       "  unsigned bit;\n"
       "  const char *const name;\n"
-      "} kBitsToOs[] = { { kOsMac, \"Mac\" },     { kOsWin, \"Windows\" },\n"
-      "                  { kOsLinux, \"Linux\" }, { kOsCrOS, \"Chrome OS\" } };");
+      "} kBitsToOs[] = { { kOsMac, \"Mac\" },\n"
+      "                  { kOsWin, \"Windows\" },\n"
+      "                  { kOsLinux, \"Linux\" },\n"
+      "                  { kOsCrOS, \"Chrome OS\" } };");
 }
 
 TEST_F(FormatTest, FormatsSmallMacroDefinitionsInSingleLine) {
@@ -4539,8 +4539,10 @@ TEST_F(FormatTest, FormatsBracedListsinColumnLayout) {
                "                  1, 1, 1, 1,\n"
                "                  /**/ /**/ };",
                getLLVMStyleWithColumns(39));
-  verifyFormat("return { { aaaaaaaaaaaaaaaaaaaaa }, { aaaaaaaaaaaaaaaaaaa },\n"
-               "         { aaaaaaaaaaaaaaaaaaaaa }, { aaaaaaaaaaaaaaaaa } };",
+  verifyFormat("return { { aaaaaaaaaaaaaaaaaaaaa },\n"
+               "         { aaaaaaaaaaaaaaaaaaa },\n"
+               "         { aaaaaaaaaaaaaaaaaaaaa },\n"
+               "         { aaaaaaaaaaaaaaaaa } };",
                getLLVMStyleWithColumns(60));
 }