[clang] [clang][ExtractAPI] combine typedef records if the underlying type's name is underscored (PR #125964)

[via cfe-commits]

https://github.com/QuietMisdreavus created https://github.com/llvm/llvm-project/pull/125964

fixes rdar://137214218

When 'typedef struct' decls are encountered, the records are combined if the underlying type is either anonymous or has the same name as the typedef. Extend this behavior to also combine records when the underlying type has an underscored name that is equivalent to the typedef name when the leading underscores are removed.

>From 75a724eacae70cb73906474a842f88d6cf22bf8f Mon Sep 17 00:00:00 2001
From: Vera Mitchell <vgm at apple.com>
Date: Wed, 5 Feb 2025 16:53:08 -0700
Subject: [PATCH] combine typedef records if the underlying type's name is
 underscored

fixes rdar://137214218

When 'typedef struct' decls are encountered, the records are combined if
the underlying type is either anonymous or has the same name as the
typedef. Extend this behavior to also combine records when the
underlying type has an underscored name that is equivalent to the
typedef name when the leading underscores are removed.
---
 .../clang/ExtractAPI/ExtractAPIVisitor.h      | 26 ++++++-
 clang/test/ExtractAPI/typedef_underscore.c    | 69 +++++++++++++++++++
 2 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 clang/test/ExtractAPI/typedef_underscore.c

diff --git a/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h b/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
index aa86e4180671144..6442b234cd929f2 100644
--- a/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
+++ b/clang/include/clang/ExtractAPI/ExtractAPIVisitor.h
@@ -1146,11 +1146,30 @@ bool ExtractAPIVisitorBase<Derived>::VisitTypedefNameDecl(
 
   StringRef Name = Decl->getName();
 
+  auto nameMatches = [&Name](TagDecl *TagDecl) {
+    StringRef TagName = TagDecl->getName();
+
+    if (TagName == Name)
+      return true;
+
+    // Also check whether the tag decl's name is the same as the typedef name
+    // with prefixed underscores
+    if (TagName.starts_with('_')) {
+      StringRef StrippedName =
+          TagName.drop_while([](char c) { return c == '_'; });
+
+      if (StrippedName == Name)
+        return true;
+    }
+
+    return false;
+  };
+
   // If the underlying type was defined as part of the typedef modify it's
   // fragments directly and pretend the typedef doesn't exist.
   if (auto *TagDecl = Decl->getUnderlyingType()->getAsTagDecl()) {
     if (TagDecl->isEmbeddedInDeclarator() && TagDecl->isCompleteDefinition() &&
-        Decl->getName() == TagDecl->getName()) {
+        nameMatches(TagDecl)) {
       SmallString<128> TagUSR;
       index::generateUSRForDecl(TagDecl, TagUSR);
       if (auto *Record = API.findRecordForUSR(TagUSR)) {
@@ -1164,6 +1183,11 @@ bool ExtractAPIVisitorBase<Derived>::VisitTypedefNameDecl(
             .append(Name, DeclarationFragments::FragmentKind::Identifier)
             .appendSemicolon();
 
+        // Replace the name and subheading in case it's underscored so we can
+        // use the non-underscored version
+        Record->Name = Name;
+        Record->SubHeading = DeclarationFragmentsBuilder::getSubHeading(Decl);
+
         return true;
       }
     }
diff --git a/clang/test/ExtractAPI/typedef_underscore.c b/clang/test/ExtractAPI/typedef_underscore.c
new file mode 100644
index 000000000000000..a42046907b46de8
--- /dev/null
+++ b/clang/test/ExtractAPI/typedef_underscore.c
@@ -0,0 +1,69 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -extract-api --pretty-sgf --emit-sgf-symbol-labels-for-testing \
+// RUN:   --product-name=TypedefChain -triple arm64-apple-macosx -x c-header %s -o %t/typedefchain-c.symbols.json -verify
+// RUN: %clang_cc1 -extract-api --pretty-sgf --emit-sgf-symbol-labels-for-testing \
+// RUN:   --product-name=TypedefChain -triple arm64-apple-macosx -x c++-header %s -o %t/typedefchain-cxx.symbols.json -verify
+
+// RUN: FileCheck %s --input-file %t/typedefchain-c.symbols.json --check-prefix MYSTRUCT
+// RUN: FileCheck %s --input-file %t/typedefchain-cxx.symbols.json --check-prefix MYSTRUCT
+typedef struct _MyStruct { } MyStruct;
+
+// MYSTRUCT-LABEL: "!testLabel": "c:@S at _MyStruct"
+// MYSTRUCT:      "accessLevel": "public",
+// MYSTRUCT:      "declarationFragments": [
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "keyword",
+// MYSTRUCT-NEXT:     "spelling": "typedef"
+// MYSTRUCT-NEXT:   },
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "text",
+// MYSTRUCT-NEXT:     "spelling": " "
+// MYSTRUCT-NEXT:   },
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "keyword",
+// MYSTRUCT-NEXT:     "spelling": "struct"
+// MYSTRUCT-NEXT:   },
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "text",
+// MYSTRUCT-NEXT:     "spelling": " "
+// MYSTRUCT-NEXT:   },
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "identifier",
+// MYSTRUCT-NEXT:     "spelling": "_MyStruct"
+// MYSTRUCT-NEXT:   },
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "text",
+// MYSTRUCT-NEXT:     "spelling": " { ... } "
+// MYSTRUCT-NEXT:   },
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "identifier",
+// MYSTRUCT-NEXT:     "spelling": "MyStruct"
+// MYSTRUCT-NEXT:   },
+// MYSTRUCT-NEXT:   {
+// MYSTRUCT-NEXT:     "kind": "text",
+// MYSTRUCT-NEXT:     "spelling": ";"
+// MYSTRUCT-NEXT:   }
+// MYSTRUCT-NEXT: ],
+// MYSTRUCT:      "kind": {
+// MYSTRUCT-NEXT:   "displayName": "Structure",
+// MYSTRUCT-NEXT:   "identifier": "c{{(\+\+)?}}.struct"
+// MYSTRUCT:           "names": {
+// MYSTRUCT-NEXT:        "navigator": [
+// MYSTRUCT-NEXT:          {
+// MYSTRUCT-NEXT:            "kind": "identifier",
+// MYSTRUCT-NEXT:            "spelling": "MyStruct"
+// MYSTRUCT-NEXT:          }
+// MYSTRUCT-NEXT:        ],
+// MYSTRUCT-NEXT:        "subHeading": [
+// MYSTRUCT-NEXT:          {
+// MYSTRUCT-NEXT:            "kind": "identifier",
+// MYSTRUCT-NEXT:            "spelling": "MyStruct"
+// MYSTRUCT-NEXT:          }
+// MYSTRUCT-NEXT:        ],
+// MYSTRUCT-NEXT:        "title": "MyStruct"
+// MYSTRUCT-NEXT:      },
+// MYSTRUCT:      "pathComponents": [
+// MYSTRUCT-NEXT:    "MyStruct"
+// MYSTRUCT-NEXT:  ]
+
+// expected-no-diagnostics