[clangd] Fix header-name completion replace ranges (#225473)

Handle header-name completion as a special case for replace edits. Its
insert range already extends past the identifier, including delimiters
such as '"' and '>'. Reuse that range for replace edits so that the
insert range remains a prefix of the replace range, as required by the
LSP specification.

Add a unit test covering this case.

Fixes llvm/llvm-project#225326

(cherry picked from commit da43ad37dcc98427fe95039b75ca037d9995d3e8)

clang-tools-extra/clangd/CodeComplete.cpp

@@ -1833,9 +1833,13 @@ private:
     }
 
     if (Opts.EnableInsertReplace) {
-      ReplaceRange.emplace();
-      ReplaceRange->start = InsertRange.start;
-      ReplaceRange->end = getEndOfCodeCompletionReplace(SM);
+      // Header-name completion always provides a replace-like range,
+      // including delimiters, even in the Insert mode.
+      const Position ReplaceRangeEnd =
+          CCContextKind == CodeCompletionContext::CCC_IncludedFile
+              ? InsertRange.end
+              : getEndOfCodeCompletionReplace(SM);
+      ReplaceRange = Range{InsertRange.start, ReplaceRangeEnd};
     }
     Filter = FuzzyMatcher(
         Recorder->CCSema->getPreprocessor().getCodeCompletionFilter());

clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp

@@ -4327,6 +4327,62 @@ TEST(CompletionTest, ReplaceRangeNoCompile) {
   EXPECT_EQ(Results.ReplaceRange, std::nullopt);
 }
 
+TEST(CompletionTest, ReplaceRangeInclude) {
+  clangd::CodeCompleteOptions Opts;
+  Opts.EnableInsertReplace = true;
+
+  TestTU TU;
+  TU.AdditionalFiles["include/sub/foo.h"] = "";
+  TU.AdditionalFiles["include/sub/u00e9/bar.h"] = "";
+  TU.ExtraArgs = {"-Iinclude"};
+
+  // Replace range starts after a preceding path component and includes the
+  // closing angle bracket.
+  const char *NestedPath = R"cpp(#include <sub/[[fo^o.h>]])cpp";
+  Annotations A(NestedPath);
+  TU.Code = A.code();
+  CodeCompleteResult Results =
+      completions(TU, A.point(), /*IndexSymbols=*/{}, Opts);
+  EXPECT_EQ(Results.InsertRange, A.range());
+  EXPECT_EQ(Results.ReplaceRange, A.range());
+
+  // Replace range starts after a preceding path component and includes the
+  // closing quote.
+  const char *WithQuote = R"cpp(#include "sub/[[fo^o.h"]])cpp";
+  A = Annotations(WithQuote);
+  TU.Code = A.code();
+  Results = completions(TU, A.point(), /*IndexSymbols=*/{}, Opts);
+  EXPECT_EQ(Results.InsertRange, A.range());
+  EXPECT_EQ(Results.ReplaceRange, A.range());
+
+  // Replace range includes the path component and its trailing separator.
+  const char *PathComponent = R"cpp(#include "[[su^b/]]foo.h")cpp";
+  A = Annotations(PathComponent);
+  TU.Code = A.code();
+  Results = completions(TU, A.point(), /*IndexSymbols=*/{}, Opts);
+  EXPECT_EQ(Results.InsertRange, A.range());
+  EXPECT_EQ(Results.ReplaceRange, A.range());
+
+  // A UCN-like escape is not interpreted in a header name.
+  TU.ExtraArgs.push_back("-fno-ms-compatibility");
+  const char *UnicodeLike = R"cpp(#include "[[su^\u00e9/]]foo.h")cpp";
+  A = Annotations(UnicodeLike);
+  TU.Code = A.code();
+  Results = completions(TU, A.point(), /*IndexSymbols=*/{}, Opts);
+  EXPECT_EQ(Results.InsertRange, A.range());
+  EXPECT_EQ(Results.ReplaceRange, A.range());
+  TU.ExtraArgs.pop_back();
+
+  // In MSVC compatibility mode, backslash is a path separator.
+  TU.ExtraArgs.push_back("-fms-compatibility");
+  const char *UnicodeLikeMs = R"cpp(#include "[[su^\]]u00e9/bar.h")cpp";
+  A = Annotations(UnicodeLikeMs);
+  TU.Code = A.code();
+  Results = completions(TU, A.point(), /*IndexSymbols=*/{}, Opts);
+  EXPECT_EQ(Results.InsertRange, A.range());
+  EXPECT_EQ(Results.ReplaceRange, A.range());
+}
+
 TEST(NoCompileCompletionTest, Basic) {
   auto Results = completionsNoCompile(R"cpp(
     void func() {