[clangd] Add CLI flag "-clang-tidy" to enable/disable running clang-tidy checks.

[sammccall]

clangd/tool/ClangdMain.cpp

214

I thought we discussed making this init(false) for now, and flipping the flag after getting feedback?

(at head this is on, but not many people run from head)

[hokein]

Set the flag to false by default.

clangd/tool/ClangdMain.cpp

static llvm::cl::opt<bool> EnableFunctionArgSnippets(
     "function-arg-placeholders",
     llvm::cl::desc("When disabled, completions contain only parentheses for "
                    "function calls. When enabled, completions also contain "
                    "placeholders for method parameters."),
     llvm::cl::init(CodeCompleteOptions().EnableFunctionArgSnippets));
 
 static llvm::cl::opt<std::string> ClangTidyChecks(
     "clang-tidy-checks",
-    llvm::cl::desc("List of clang-tidy checks to run (this will override "
-                   ".clang-tidy files)"),
+    llvm::cl::desc(
+        "List of clang-tidy checks to run (this will override "
+        ".clang-tidy files). Only meaningful when -clang-tidy flag is on."),
     llvm::cl::init(""));
 
+static llvm::cl::opt<bool> EnableClangTidy(
+    "clang-tidy",
+    llvm::cl::desc("Enable clang-tidy diagnostics."),
+    llvm::cl::init(true));
+
 static llvm::cl::opt<bool> SuggestMissingIncludes(
     "suggest-missing-includes",
     llvm::cl::desc("Attempts to fix diagnostic errors caused by missing "
                    "includes using index."),
     llvm::cl::init(false));
 
 namespace {
 
#endif
   } else {
     TransportLayer = newJSONTransport(
         stdin, llvm::outs(),
         InputMirrorStream ? InputMirrorStream.getPointer() : nullptr,
         PrettyPrint, InputStyle);
   }
 
   // Create an empty clang-tidy option.
+  std::unique_ptr<tidy::ClangTidyOptionsProvider> ClangTidyOptProvider;
+  if (EnableClangTidy) {
     auto OverrideClangTidyOptions = tidy::ClangTidyOptions::getDefaults();
     OverrideClangTidyOptions.Checks = ClangTidyChecks;
-  tidy::FileOptionsProvider ClangTidyOptProvider(
+    ClangTidyOptProvider = llvm::make_unique<tidy::FileOptionsProvider>(
         tidy::ClangTidyGlobalOptions(),
         /* Default */ tidy::ClangTidyOptions::getDefaults(),
         /* Override */ OverrideClangTidyOptions, FSProvider.getFileSystem());
-  Opts.ClangTidyOptProvider = &ClangTidyOptProvider;
+  }
+  Opts.ClangTidyOptProvider = ClangTidyOptProvider.get();
   Opts.SuggestMissingIncludes = SuggestMissingIncludes;
   ClangdLSPServer LSPServer(
       *TransportLayer, FSProvider, CCOpts, CompileCommandsDirPath,
       /*UseDirBasedCDB=*/CompileArgsFrom == FilesystemCompileArgs, Opts);
   llvm::set_thread_name("clangd.main");
   return LSPServer.run() ? 0
                          : static_cast<int>(ErrorResultCode::NoShutdownRequest);
 }