[clang] [clang-format] Skip PP directives when determining brace kind (PR #69473)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-format

Author: Emilia Kond (rymiel)

<details>
<summary>Changes</summary>

Pull request #<!-- -->65409 changed the brace kind heuristic to not treat a preprocessor if directive as a in statement, however, this caused some regressions.

If the contents of a brace don't immediately determine the brace kind, the heuristic will look at the characters immediately before and after the closing brace to determine the brace type.

Unfortunately, if the closing brace was preceded by a preprocessor directive, for example `#endif`, the preceding token was `endif`, seen as just an identifier, so the braces were understood as a braced list.

This patch fixes this behaviour by skipping all preprocessor directives when calculating brace types. Comments were already being skipped, so now preprocessor lines are skipped alongside comments.

Fixes https://github.com/llvm/llvm-project/issues/68404

---
Full diff: https://github.com/llvm/llvm-project/pull/69473.diff


2 Files Affected:

- (modified) clang/lib/Format/UnwrappedLineParser.cpp (+14-9) 
- (modified) clang/unittests/Format/TokenAnnotatorTest.cpp (+15) 


``````````diff
diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 708b70489a114e3..90e68e875fd462b 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -491,11 +491,19 @@ void UnwrappedLineParser::calculateBraceTypes(bool ExpectClassBody) {
   SmallVector<StackEntry, 8> LBraceStack;
   assert(Tok->is(tok::l_brace));
   do {
-    // Get next non-comment token.
-    FormatToken *NextTok;
-    do {
-      NextTok = Tokens->getNextToken();
-    } while (NextTok->is(tok::comment));
+    // Get next non-comment, non-preprocessor token.
+    FormatToken *NextTok = Tokens->getNextToken();
+    while (NextTok->is(tok::comment) ||
+           (NextTok->is(tok::hash) && isOnNewLine(*NextTok))) {
+      while (NextTok->is(tok::comment))
+        NextTok = Tokens->getNextToken();
+      while (NextTok->is(tok::hash) && isOnNewLine(*NextTok)) {
+        ScopedMacroState MacroState(*Line, Tokens, NextTok);
+        do {
+          NextTok = Tokens->getNextToken();
+        } while (NextTok->isNot(tok::eof));
+      }
+    }
 
     switch (Tok->Tok.getKind()) {
     case tok::l_brace:
@@ -611,12 +619,9 @@ void UnwrappedLineParser::calculateBraceTypes(bool ExpectClassBody) {
       if (Tok->isNot(TT_StatementMacro))
         break;
       [[fallthrough]];
-    case tok::kw_if:
-      if (PrevTok->is(tok::hash))
-        break;
-      [[fallthrough]];
     case tok::at:
     case tok::semi:
+    case tok::kw_if:
     case tok::kw_while:
     case tok::kw_for:
     case tok::kw_switch:
diff --git a/clang/unittests/Format/TokenAnnotatorTest.cpp b/clang/unittests/Format/TokenAnnotatorTest.cpp
index 2d046947996693f..8c76823fdeb6ecd 100644
--- a/clang/unittests/Format/TokenAnnotatorTest.cpp
+++ b/clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -2134,6 +2134,7 @@ TEST_F(TokenAnnotatorTest, UnderstandConstructors) {
   EXPECT_TOKEN(Tokens[11], tok::l_paren, TT_Unknown);
   EXPECT_TOKEN(Tokens[12], tok::r_paren, TT_Unknown);
   EXPECT_TOKEN(Tokens[13], tok::l_brace, TT_FunctionLBrace);
+  EXPECT_BRACE_KIND(Tokens[13], BK_Block);
 
   Tokens = annotate("Class::Class() : BaseClass{}, Member{} {}");
   ASSERT_EQ(Tokens.size(), 16u) << Tokens;
@@ -2146,6 +2147,20 @@ TEST_F(TokenAnnotatorTest, UnderstandConstructors) {
   EXPECT_TOKEN(Tokens[11], tok::l_brace, TT_Unknown);
   EXPECT_TOKEN(Tokens[12], tok::r_brace, TT_Unknown);
   EXPECT_TOKEN(Tokens[13], tok::l_brace, TT_FunctionLBrace);
+  EXPECT_BRACE_KIND(Tokens[13], BK_Block);
+
+  Tokens = annotate("class Class {\n"
+                    "  Class() : BaseClass() {\n"
+                    "#if 0\n"
+                    "    // comment\n"
+                    "#endif\n"
+                    "  }\n"
+                    "  Class f();\n"
+                    "}");
+  ASSERT_EQ(Tokens.size(), 25u) << Tokens;
+  EXPECT_TOKEN(Tokens[6], tok::colon, TT_CtorInitializerColon);
+  EXPECT_TOKEN(Tokens[10], tok::l_brace, TT_FunctionLBrace);
+  EXPECT_BRACE_KIND(Tokens[10], BK_Block);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsConditionParens) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/69473