[clangd] Don't perform rename when the refs result from index is incomplete.

[hokein]

Summary

Also do an early return if the number of affected files > limit to save
some unnecessary FileURI computations.

[ilya-biryukov]

LGTM

clang-tools-extra/clangd/refactor/Rename.cpp

Range toRange(const SymbolLocation &L) {
   R.start.character = L.Start.column();
   R.end.line = L.End.line();
   R.end.character = L.End.column();
   return R;
 };
 
 // Return all rename occurrences (per the index) outside of the main file,
 // grouped by the absolute file path.
-llvm::StringMap<std::vector<Range>>
+llvm::Expected<llvm::StringMap<std::vector<Range>>>
 findOccurrencesOutsideFile(const NamedDecl &RenameDecl,
                            llvm::StringRef MainFile, const SymbolIndex &Index) {
   RefsRequest RQuest;
   RQuest.IDs.insert(*getSymbolID(&RenameDecl));
 
-  // Absolute file path => rename ocurrences in that file.
+  // Absolute file path => rename occurrences in that file.
   llvm::StringMap<std::vector<Range>> AffectedFiles;
-  Index.refs(RQuest, [&](const Ref &R) {
+  // FIXME: make the limit customizable.
+  static constexpr size_t MaxLimitFiles = 50;
+  bool HasMore = Index.refs(RQuest, [&](const Ref &R) {
+    if (AffectedFiles.size() > MaxLimitFiles)
+      return;
     if (auto RefFilePath = filePath(R.Location, /*HintFilePath=*/MainFile)) {
       if (*RefFilePath != MainFile)
         AffectedFiles[*RefFilePath].push_back(toRange(R.Location));
     }
   });
+
+  if (AffectedFiles.size() > MaxLimitFiles)
+    return llvm::make_error<llvm::StringError>(
+        llvm::formatv("The number of affected files exceeds the max limit {0}",
+                      MaxLimitFiles),
+        llvm::inconvertibleErrorCode());
+  if (HasMore) {
+    return llvm::make_error<llvm::StringError>(
+        llvm::formatv("The symbol {0} has too many occurrences",
+                      RenameDecl.getQualifiedNameAsString()),
+        llvm::inconvertibleErrorCode());
+  }
+
   return AffectedFiles;
 }
 
 // Index-based rename, it renames all occurrences outside of the main file.
 //
 // The cross-file rename is purely based on the index, as we don't want to
 // build all ASTs for affected files, which may cause a performance hit.
 // We choose to trade off some correctness for performance and scalability.

 // FIXME: our index may return implicit references, which are non-eligitble
 //        for rename, we should filter out these references.
 llvm::Expected<FileEdits> renameOutsideFile(
     const NamedDecl &RenameDecl, llvm::StringRef MainFilePath,
     llvm::StringRef NewName, const SymbolIndex &Index,
     llvm::function_ref<llvm::Expected<std::string>(PathRef)> GetFileContent) {
   auto AffectedFiles =
       findOccurrencesOutsideFile(RenameDecl, MainFilePath, Index);
-  // FIXME: make the limit customizable.
-  static constexpr size_t MaxLimitFiles = 50;
-  if (AffectedFiles.size() >= MaxLimitFiles)
-    return llvm::make_error<llvm::StringError>(
-        llvm::formatv(
-            "The number of affected files exceeds the max limit {0}: {1}",
-            MaxLimitFiles, AffectedFiles.size()),
-        llvm::inconvertibleErrorCode());
-
+  if (!AffectedFiles)
+    return AffectedFiles.takeError();
   FileEdits Results;
-  for (auto &FileAndOccurrences : AffectedFiles) {
+  for (auto &FileAndOccurrences : *AffectedFiles) {
     llvm::StringRef FilePath = FileAndOccurrences.first();
 
     auto AffectedFileCode = GetFileContent(FilePath);
     if (!AffectedFileCode) {
       elog("Fail to read file content: {0}", AffectedFileCode.takeError());
       continue;
     }
     auto RenameEdit = buildRenameEdit(

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

TEST(RenameTests, CrossFile) {
   Results = rename({MainCode.point(), NewName, AST, MainFilePath, Index.get(),
                     /*CrossFile=*/true, GetDirtyBuffer});
   ASSERT_TRUE(bool(Results)) << Results.takeError();
   EXPECT_THAT(
       applyEdits(std::move(*Results)),
       UnorderedElementsAre(
           Pair(Eq(BarPath), Eq(expectedResult(BarCode, NewName))),
           Pair(Eq(MainFilePath), Eq(expectedResult(MainCode, NewName)))));
+
+  // Run rename on a pagination index which couldn't return all refs in one
+  // request, we reject rename on this case.
+  class PaginationIndex : public SymbolIndex {
+    bool refs(const RefsRequest &Req,
+              llvm::function_ref<void(const Ref &)> Callback) const override {
+      return true; // has more references
+    }
+
+    bool fuzzyFind(
+        const FuzzyFindRequest &Req,
+        llvm::function_ref<void(const Symbol &)> Callback) const override {
+      return false;
+    }
+    void
+    lookup(const LookupRequest &Req,
+           llvm::function_ref<void(const Symbol &)> Callback) const override {}
+
+    void relations(const RelationsRequest &Req,
+                   llvm::function_ref<void(const SymbolID &, const Symbol &)>
+                       Callback) const override {}
+    size_t estimateMemoryUsage() const override { return 0; }
+  } PIndex;
+  Results = rename({MainCode.point(), NewName, AST, MainFilePath, &PIndex,
+                    /*CrossFile=*/true, GetDirtyBuffer});
+  EXPECT_FALSE(Results);
+  EXPECT_THAT(llvm::toString(Results.takeError()),
+              testing::HasSubstr("too many occurrences"));
 }
 
 TEST(CrossFileRenameTests, CrossFileOnLocalSymbol) {
   // cross-file rename should work for function-local symbols, even there is no
   // index provided.
   Annotations Code("void f(int [[abc]]) { [[a^bc]] = 3; }");
   auto TU = TestTU::withCode(Code.code());
   auto Path = testPath(TU.Filename);