[clangd] Disable typo correction when doing code completion.

[ilya-biryukov]

LGTM

clangd/CodeComplete.cpp

if (!SS) {
     //        "using namespace std; namespace foo {v^}" =>
     //        foo::value > std::vector > boost::variant
     return GetAllAccessibleScopes(CCContext).scopesForIndexQuery();
   }
 
   // Qualified completion ("std::vec^"), we have two cases depending on whether
   // the qualifier can be resolved by Sema.
   if ((*SS)->isValid()) { // Resolved qualifier.
-    // FIXME: Disable Sema typo correction during code completion.
-    // The resolved qualifier might not perfectly match the written qualifier.
-    // e.g. "namespace clang { clangd::^ }", we will get "clang" declaration
-    // for completion "clangd::".
     return GetAllAccessibleScopes(CCContext).scopesForIndexQuery();
   }
 
   // Unresolved qualifier.
   // FIXME: When Sema can resolve part of a scope chain (e.g.
   // "known::unknown::id"), we should expand the known part ("known::") rather
   // than treating the whole thing as unknown.
   SpecifiedScope Info;
Input.Preamble->CanReuse(*CI, ContentsBuffer.get(), Bounds,
                              Input.VFS.get());
   }
   auto Clang = prepareCompilerInstance(
       std::move(CI), Input.Preamble, std::move(ContentsBuffer),
       std::move(Input.PCHs), std::move(Input.VFS), DummyDiagsConsumer);
   auto &DiagOpts = Clang->getDiagnosticOpts();
   DiagOpts.IgnoreWarnings = true;
 
+  // Disable typo correction in Sema.
+  Clang->getLangOpts().SpellChecking = false;
+
   auto &FrontendOpts = Clang->getFrontendOpts();
   FrontendOpts.SkipFunctionBodies = true;
   FrontendOpts.CodeCompleteOpts = Options;
   FrontendOpts.CodeCompletionAt.FileName = Input.FileName;
   FrontendOpts.CodeCompletionAt.Line = Input.Pos.line + 1;
   FrontendOpts.CodeCompletionAt.Column = Input.Pos.character + 1;
 
   Clang->setCodeCompletionConsumer(Consumer.release());

unittests/clangd/CodeCompleteTests.cpp

TEST(CompletionTest, DynamicIndexMultiFile) {
   EXPECT_THAT(Results.items, Has("XYZ", CompletionItemKind::Class));
   EXPECT_THAT(Results.items, Has("foo", CompletionItemKind::Function));
   EXPECT_THAT(Results.items, Has("XXX", CompletionItemKind::Class));
   EXPECT_THAT(Results.items, Contains(AllOf(Named("fooooo"), Filter("fooooo"),
                                             Kind(CompletionItemKind::Function),
                                             Doc("Doooc"), Detail("void"))));
 }
 
+TEST(CodeCompleteTest, DisableTypoCorrection) {
+  auto Results = completions(R"cpp(
+     namespace clang { int v; }
+     void f() { clangd::^
+  )cpp");
+  EXPECT_TRUE(Results.items.empty());
+}
+
 SignatureHelp signatures(StringRef Text) {
   MockFSProvider FS;
   MockCompilationDatabase CDB;
   IgnoreDiagnostics DiagConsumer;
   ClangdServer Server(CDB, DiagConsumer, FS, getDefaultAsyncThreadsCount(),
                       /*StorePreamblesInMemory=*/true);
   auto File = getVirtualTestFilePath("foo.cpp");
   Annotations Test(Text);