[clang-format] Fix DefSeparator empty line issues

- Add or remove empty lines surrounding union blocks.
- Fixes #53229, in which
  keywords like class and struct in a line ending with left brace or
  whose next line is left brace only, will be falsely recognized as
  definition line, causing extra empty lines inserted surrounding blocks
  with no need to be formatted.

Reviewed By: MyDeveloperDay, curdeius, HazardyKnusperkeks, owenpan
Differential Revision: https://reviews.llvm.org/D119067

(cherry picked from commit a70549a)

Author: ksyx

clang/lib/Format/DefinitionBlockSeparator.cpp

@@ -35,19 +35,31 @@ void DefinitionBlockSeparator::separateBlocks(
   const bool IsNeverStyle =
       Style.SeparateDefinitionBlocks == FormatStyle::SDS_Never;
   const AdditionalKeywords &ExtraKeywords = Tokens.getKeywords();
-  auto LikelyDefinition = [this, ExtraKeywords](const AnnotatedLine *Line,
-                                                bool ExcludeEnum = false) {
+  auto GetBracketLevelChange = [](const FormatToken *Tok) {
+    if (Tok->isOneOf(tok::l_brace, tok::l_paren, tok::l_square))
+      return 1;
+    if (Tok->isOneOf(tok::r_brace, tok::r_paren, tok::r_square))
+      return -1;
+    return 0;
+  };
+  auto LikelyDefinition = [&](const AnnotatedLine *Line,
+                              bool ExcludeEnum = false) {
     if ((Line->MightBeFunctionDecl && Line->mightBeFunctionDefinition()) ||
         Line->startsWithNamespace())
       return true;
-    FormatToken *CurrentToken = Line->First;
-    while (CurrentToken) {
-      if (CurrentToken->isOneOf(tok::kw_class, tok::kw_struct) ||
-          (Style.isJavaScript() && CurrentToken->is(ExtraKeywords.kw_function)))
-        return true;
-      if (!ExcludeEnum && CurrentToken->is(tok::kw_enum))
-        return true;
-      CurrentToken = CurrentToken->Next;
+    int BracketLevel = 0;
+    for (const FormatToken *CurrentToken = Line->First; CurrentToken;
+         CurrentToken = CurrentToken->Next) {
+      if (BracketLevel == 0) {
+        if ((CurrentToken->isOneOf(tok::kw_class, tok::kw_struct,
+                                   tok::kw_union) ||
+             (Style.isJavaScript() &&
+              CurrentToken->is(ExtraKeywords.kw_function))))
+          return true;
+        if (!ExcludeEnum && CurrentToken->is(tok::kw_enum))
+          return true;
+      }
+      BracketLevel += GetBracketLevelChange(CurrentToken);
     }
     return false;
   };
@@ -102,14 +114,17 @@ void DefinitionBlockSeparator::separateBlocks(
              IsPPConditional(OpeningLineIndex - 1);
     };
     const auto HasEnumOnLine = [&]() {
-      FormatToken *CurrentToken = CurrentLine->First;
       bool FoundEnumKeyword = false;
-      while (CurrentToken) {
-        if (CurrentToken->is(tok::kw_enum))
-          FoundEnumKeyword = true;
-        else if (FoundEnumKeyword && CurrentToken->is(tok::l_brace))
-          return true;
-        CurrentToken = CurrentToken->Next;
+      int BracketLevel = 0;
+      for (const FormatToken *CurrentToken = CurrentLine->First; CurrentToken;
+           CurrentToken = CurrentToken->Next) {
+        if (BracketLevel == 0) {
+          if (CurrentToken->is(tok::kw_enum))
+            FoundEnumKeyword = true;
+          else if (FoundEnumKeyword && CurrentToken->is(tok::l_brace))
+            return true;
+        }
+        BracketLevel += GetBracketLevelChange(CurrentToken);
       }
       return FoundEnumKeyword && I + 1 < Lines.size() &&
              Lines[I + 1]->First->is(tok::l_brace);

clang/unittests/Format/DefinitionBlockSeparatorTest.cpp

@@ -109,6 +109,15 @@ TEST_F(DefinitionBlockSeparatorTest, Basic) {
                "};",
                Style);
 
+  verifyFormat("union foo {\n"
+               "  int i, j;\n"
+               "};\n"
+               "\n"
+               "union bar {\n"
+               "  int j, k;\n"
+               "};",
+               Style);
+
   verifyFormat("class foo {\n"
                "  int i, j;\n"
                "};\n"
@@ -311,6 +320,9 @@ TEST_F(DefinitionBlockSeparatorTest, Always) {
                       "int bar3(int j, int k, const enum Bar b) {\n"
                       "  // A comment\n"
                       "  int r = j % k;\n"
+                      "  if (struct S = getS()) {\n"
+                      "    // if condition\n"
+                      "  }\n"
                       "  return r;\n"
                       "}\n";
   std::string Postfix = "\n"
@@ -364,6 +376,9 @@ TEST_F(DefinitionBlockSeparatorTest, Never) {
                         "int bar3(int j, int k, const enum Bar b) {\n"
                         "  // A comment\n"
                         "  int r = j % k;\n"
+                        "  if (struct S = getS()) {\n"
+                        "    // if condition\n"
+                        "  }\n"
                         "  return r;\n"
                         "}\n"
                         "} // namespace";
@@ -425,6 +440,10 @@ TEST_F(DefinitionBlockSeparatorTest, OpeningBracketOwnsLine) {
                "{\n"
                "  // A comment\n"
                "  int r = j % k;\n"
+               "  if (struct S = getS())\n"
+               "  {\n"
+               "    // if condition\n"
+               "  }\n"
                "  return r;\n"
                "}\n"
                "} // namespace NS",
@@ -473,6 +492,9 @@ TEST_F(DefinitionBlockSeparatorTest, Leave) {
                         "int bar3(int j, int k, const enum Bar b) {\n"
                         "  // A comment\n"
                         "  int r = j % k;\n"
+                        "  if (struct S = getS()) {\n"
+                        "    // if condition\n"
+                        "  }\n"
                         "  return r;\n"
                         "}\n"
                         "} // namespace";