[clang-tools-extra] Fixes clangd/clangd#1797 (PR #158461)
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Sat Sep 13 23:52:00 PDT 2025
https://github.com/JVApen created https://github.com/llvm/llvm-project/pull/158461
Do not restrict HeaderSourceSwitch to switching between .h and .cpp. For templates, the relevant 'source' is the header containing the implementation of the templated functions.
Instead of considering every symbol in the current file as relevant, we restrict it to those that either have the declaration or definition in that file.
>From d828397b1ece13b9617b54e5bd75f00c2c69fd64 Mon Sep 17 00:00:00 2001
From: JVApen <vanantwerpenjeroen at gmail.com>
Date: Sat, 13 Sep 2025 10:22:28 +0200
Subject: [PATCH] Fixes clangd/clangd#1797
Do not restrict HeaderSourceSwitch to switching between .h and .cpp.
For templates, the relevant 'source' is the header containing the implementation of the templated functions.
Instead of considering every symbol in the current file as relevant, we restrict it to those that either have the declaration or definition in that file.
---
.../clangd/HeaderSourceSwitch.cpp | 42 +++--
.../unittests/HeaderSourceSwitchTests.cpp | 158 +++++++++++++++++-
2 files changed, 183 insertions(+), 17 deletions(-)
diff --git a/clang-tools-extra/clangd/HeaderSourceSwitch.cpp b/clang-tools-extra/clangd/HeaderSourceSwitch.cpp
index ee4bea1401490..494760d6ffdd3 100644
--- a/clang-tools-extra/clangd/HeaderSourceSwitch.cpp
+++ b/clang-tools-extra/clangd/HeaderSourceSwitch.cpp
@@ -82,26 +82,36 @@ std::optional<Path> getCorrespondingHeaderOrSource(PathRef OriginalFile,
Request.IDs.insert(ID);
}
llvm::StringMap<int> Candidates; // Target path => score.
- auto AwardTarget = [&](const char *TargetURI) {
- if (auto TargetPath = URI::resolve(TargetURI, OriginalFile)) {
- if (!pathEqual(*TargetPath, OriginalFile)) // exclude the original file.
- ++Candidates[*TargetPath];
- } else {
- elog("Failed to resolve URI {0}: {1}", TargetURI, TargetPath.takeError());
- }
- };
- // If we switch from a header, we are looking for the implementation
- // file, so we use the definition loc; otherwise we look for the header file,
- // we use the decl loc;
+ // When in the implementation file, we always search for the header file,
+ // using the decl loc. When we are in a header, this usually implies searching
+ // for implementation, for which we use the definition loc. For templates, we
+ // can have separate implementation headers, which behave as an implementation
+ // file. As such, we always have to add the decl loc and conditionally
+ // definition loc.
//
// For each symbol in the original file, we get its target location (decl or
// def) from the index, then award that target file.
- const bool IsHeader = isHeaderFile(OriginalFile, AST.getLangOpts());
+#ifdef CLANGD_PATH_CASE_INSENSITIVE
+ auto pathEqual = [](const llvm::StringRef &l, const llvm::StringRef &r) {
+ return l.equals_insensitive(r);
+ };
+#else
+ auto pathEqual = [](const llvm::StringRef &l, const llvm::StringRef &r) {
+ return l.equals(r);
+ };
+#endif
Index->lookup(Request, [&](const Symbol &Sym) {
- if (IsHeader)
- AwardTarget(Sym.Definition.FileURI);
- else
- AwardTarget(Sym.CanonicalDeclaration.FileURI);
+ auto TargetPathDefinition =
+ URI::resolve(Sym.Definition.FileURI, OriginalFile);
+ auto TargetPathDeclaration =
+ URI::resolve(Sym.CanonicalDeclaration.FileURI, OriginalFile);
+ if (!TargetPathDefinition || !TargetPathDeclaration)
+ return;
+ if (pathEqual(*TargetPathDefinition, OriginalFile)) {
+ if (!pathEqual(*TargetPathDeclaration, OriginalFile))
+ ++Candidates[*TargetPathDeclaration];
+ } else if (pathEqual(*TargetPathDeclaration, OriginalFile))
+ ++Candidates[*TargetPathDefinition];
});
// FIXME: our index doesn't have any interesting information (this could be
// that the background-index is not finished), we should use the decl/def
diff --git a/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp b/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp
index e600207de458a..8dd480968fdc6 100644
--- a/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp
+++ b/clang-tools-extra/clangd/unittests/HeaderSourceSwitchTests.cpp
@@ -223,6 +223,162 @@ TEST(HeaderSourceSwitchTest, FromHeaderToSource) {
}
}
+TEST(HeaderSourceSwitchTest, FromHeaderToImplHeader) {
+ // build a proper index, which contains symbols:
+ // A_Sym1, declared in TestTU.h, defined in a_ext.h
+ // B_Sym[1-2], declared in TestTU.h, defined in b_ext.h
+ SymbolSlab::Builder AllSymbols;
+ auto addHeader = [&](auto implName, auto declarationContent,
+ auto implContent) {
+ TestTU Testing;
+ Testing.ExtraArgs.push_back(
+ "-xc++-header"); // inform clang this is a header.
+
+ Testing.Filename = implName;
+ Testing.Code = implContent;
+ Testing.HeaderFilename = "TestTU.h";
+ Testing.HeaderCode = declarationContent;
+
+ for (auto &Sym : Testing.headerSymbols())
+ AllSymbols.insert(Sym);
+ };
+
+ addHeader("a_ext.h", "template<typename T> void A_Sym1();",
+ "template<typename T> void A_Sym1() {};");
+ addHeader("b_ext.h", R"cpp(
+ template<typename T> void B_Sym1();
+ template<typename T> void B_Sym2();
+ template<typename T> void B_Sym3_NoDef();
+ )cpp",
+ R"cpp(
+ template<typename T> void B_Sym1() {}
+ template<typename T> void B_Sym2() {}
+ )cpp");
+ auto Index = MemIndex::build(std::move(AllSymbols).build(), {}, {});
+
+ // Test for switch from .h header to .cc source
+ struct {
+ llvm::StringRef HeaderCode;
+ std::optional<std::string> ExpectedSource;
+ } TestCases[] = {
+ {"// empty, no header found", std::nullopt},
+ {R"cpp(
+ // no definition found in the index.
+ template<typename T> void NonDefinition();
+ )cpp",
+ std::nullopt},
+ {R"cpp(
+ template<typename T> void A_Sym1();
+ )cpp",
+ testPath("a_ext.h")},
+ {R"cpp(
+ // b_ext.h wins.
+ template<typename T> void A_Sym1();
+ template<typename T> void B_Sym1();
+ template<typename T> void B_Sym2();
+ )cpp",
+ testPath("b_ext.h")},
+ {R"cpp(
+ // a_ext.h and b_ext.h have same scope, but a_ext.h because "a_ext.h" < "b_ext.h".
+ template<typename T> void A_Sym1();
+ template<typename T> void B_Sym1();
+ )cpp",
+ testPath("a_ext.h")},
+
+ {R"cpp(
+ // We don't have definition in the index, so stay in the header.
+ template<typename T> void B_Sym3_NoDef();
+ )cpp",
+ std::nullopt},
+ };
+ for (const auto &Case : TestCases) {
+ TestTU TU = TestTU::withCode(Case.HeaderCode);
+ TU.Filename = "TestTU.h";
+ TU.ExtraArgs.push_back("-xc++-header"); // inform clang this is a header.
+ auto HeaderAST = TU.build();
+ EXPECT_EQ(Case.ExpectedSource,
+ getCorrespondingHeaderOrSource(testPath(TU.Filename), HeaderAST,
+ Index.get()));
+ }
+}
+
+TEST(HeaderSourceSwitchTest, FromImplHeaderToHeader) {
+ // build a proper index, which contains symbols:
+ // A_Sym1, declared in TestTU.h, defined in a_ext.h
+ // B_Sym[1-2], declared in TestTU.h, defined in b_ext.h
+ SymbolSlab::Builder AllSymbols;
+ auto addHeader = [&](auto declName, auto declContent, auto implContent) {
+ TestTU Testing;
+ Testing.ExtraArgs.push_back(
+ "-xc++-header"); // inform clang this is a header.
+
+ Testing.Filename = "TestTU.h";
+ Testing.Code = implContent;
+ Testing.HeaderFilename = declName;
+ Testing.HeaderCode = declContent;
+
+ for (auto &Sym : Testing.headerSymbols())
+ AllSymbols.insert(Sym);
+ };
+
+ addHeader("a.h", "template<typename T> void A_Sym1();",
+ "template<typename T> void A_Sym1() {};");
+ addHeader("b.h", R"cpp(
+ template<typename T> void B_Sym1();
+ template<typename T> void B_Sym2();
+ template<typename T> void B_Sym3_NoDef();
+ )cpp",
+ R"cpp(
+ template<typename T> void B_Sym1() {}
+ template<typename T> void B_Sym2() {}
+ )cpp");
+ auto Index = MemIndex::build(std::move(AllSymbols).build(), {}, {});
+
+ // Test for switch from .h header to .cc source
+ struct {
+ llvm::StringRef HeaderCode;
+ std::optional<std::string> ExpectedSource;
+ } TestCases[] = {
+ {"// empty, no header found", std::nullopt},
+ {R"cpp(
+ // no definition found in the index.
+ template<typename T> void NonDefinition(){}
+ )cpp",
+ std::nullopt},
+ {R"cpp(
+ template<typename T> void A_Sym1(){}
+ )cpp",
+ testPath("a.h")},
+ {R"cpp(
+ // b.h wins.
+ template<typename T> void A_Sym1(){}
+ template<typename T> void B_Sym1(){}
+ template<typename T> void B_Sym2(){}
+ )cpp",
+ testPath("b.h")},
+ {R"cpp(
+ // a.h and b.h have same scope, but a.h because "a.h" < "b.h".
+ template<typename T> void A_Sym1(){}
+ template<typename T> void B_Sym1(){}
+ )cpp",
+ testPath("a.h")},
+
+ {R"cpp(
+ // We don't have definition in the index, so stay in the header.
+ template<typename T> void B_Sym3_NoDef();
+ )cpp",
+ std::nullopt},
+ };
+ for (const auto &Case : TestCases) {
+ TestTU TU = TestTU::withCode(Case.HeaderCode);
+ TU.Filename = "TestTU.h";
+ TU.ExtraArgs.push_back("-xc++-header"); // inform clang this is a header.
+ auto HeaderAST = TU.build();
+ EXPECT_EQ(Case.ExpectedSource,
+ getCorrespondingHeaderOrSource(testPath(TU.Filename), HeaderAST,
+ Index.get()));
+ }
+}
TEST(HeaderSourceSwitchTest, FromSourceToHeader) {
// build a proper index, which contains symbols:
// A_Sym1, declared in a.h, defined in TestTU.cpp
@@ -281,7 +437,7 @@ TEST(HeaderSourceSwitchTest, FromSourceToHeader) {
};
for (const auto &Case : TestCases) {
TestTU TU = TestTU::withCode(Case.SourceCode);
- TU.Filename = "Test.cpp";
+ TU.Filename = "TestTU.cpp";
auto AST = TU.build();
EXPECT_EQ(Case.ExpectedResult,
getCorrespondingHeaderOrSource(testPath(TU.Filename), AST,
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