[clang] [clang-format] Allow ternary in all templates (PR #96801)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-format

Author: Emilia Kond (rymiel)

<details>
<summary>Changes</summary>

Currently, question mark and colon tokens are not allowed between angle brackets, as a template argument, if we are in an expression context.

However, expressions can still allowed in non-expression contexts, leading to inconsistent formatting.

Removing this check entirely fixes this issue, and, surprisingly, breaks no tests.

Fixes https://github.com/llvm/llvm-project/issues/81385

---
Full diff: https://github.com/llvm/llvm-project/pull/96801.diff


2 Files Affected:

- (modified) clang/lib/Format/TokenAnnotator.cpp (+1-8) 
- (modified) clang/unittests/Format/TokenAnnotatorTest.cpp (+18) 


``````````diff
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 89e134144d433..03082cd2742c8 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -176,10 +176,6 @@ class AnnotatingParser {
     Left->ParentBracket = Contexts.back().ContextKind;
     ScopedContextCreator ContextCreator(*this, tok::less, 12);
 
-    // If this angle is in the context of an expression, we need to be more
-    // hesitant to detect it as opening template parameters.
-    bool InExprContext = Contexts.back().IsExpression;
-
     Contexts.back().IsExpression = false;
     // If there's a template keyword before the opening angle bracket, this is a
     // template parameter, not an argument.
@@ -231,11 +227,8 @@ class AnnotatingParser {
         next();
         continue;
       }
-      if (CurrentToken->isOneOf(tok::r_paren, tok::r_square, tok::r_brace) ||
-          (CurrentToken->isOneOf(tok::colon, tok::question) && InExprContext &&
-           !Style.isCSharp() && !Style.isProto())) {
+      if (CurrentToken->isOneOf(tok::r_paren, tok::r_square, tok::r_brace))
         return false;
-      }
       // If a && or || is found and interpreted as a binary operator, this set
       // of angles is likely part of something like "a < b && c > d". If the
       // angles are inside an expression, the ||/&& might also be a binary
diff --git a/clang/unittests/Format/TokenAnnotatorTest.cpp b/clang/unittests/Format/TokenAnnotatorTest.cpp
index d3b310fe59527..5d83d8a0c4429 100644
--- a/clang/unittests/Format/TokenAnnotatorTest.cpp
+++ b/clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -567,6 +567,24 @@ TEST_F(TokenAnnotatorTest, UnderstandsGreaterAfterTemplateCloser) {
   EXPECT_TOKEN(Tokens[8], tok::greater, TT_BinaryOperator);
 }
 
+TEST_F(TokenAnnotatorTest, UnderstandsTernaryInTemplate) {
+  // IsExpression = false
+  auto Tokens = annotate("foo<true ? 1 : 2>();");
+  ASSERT_EQ(Tokens.size(), 12u) << Tokens;
+  EXPECT_TOKEN(Tokens[1], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[3], tok::question, TT_ConditionalExpr);
+  EXPECT_TOKEN(Tokens[5], tok::colon, TT_ConditionalExpr);
+  EXPECT_TOKEN(Tokens[7], tok::greater, TT_TemplateCloser);
+
+  // IsExpression = true
+  Tokens = annotate("return foo<true ? 1 : 2>();");
+  ASSERT_EQ(Tokens.size(), 13u) << Tokens;
+  EXPECT_TOKEN(Tokens[2], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[4], tok::question, TT_ConditionalExpr);
+  EXPECT_TOKEN(Tokens[6], tok::colon, TT_ConditionalExpr);
+  EXPECT_TOKEN(Tokens[8], tok::greater, TT_TemplateCloser);
+}
+
 TEST_F(TokenAnnotatorTest, UnderstandsNonTemplateAngleBrackets) {
   auto Tokens = annotate("return a < b && c > d;");
   ASSERT_EQ(Tokens.size(), 10u) << Tokens;

``````````

</details>


https://github.com/llvm/llvm-project/pull/96801