[clangd] Add command line option for ClangTidyConfig

[njames93]

Summary

Adds a command line flag clang-tidy-config for specifing configuration of checks, in much the same way that clang-tidy does.

[sammccall]

Good/bad news on timing here...

I'd like to introduce a config system (user config file, but also eventually in-project .clangd files, extensible over LSP etc).
It'll provide a generic way to apply different config to different files.
And it'll be YAML files on disk so it'll be simpler to supply such structured config (and still possible to provide config on the command-line).
I was literally going to send the design doc out today: http://tinyurl.com/clangd-config

This would replace most of our separate "user-pref"-like command-line flags (deprecate and maybe eventually remove).
As such I'm not sure introducing another one for fairly deep config is a good idea.

On the other hand, the scope for the config would be deliberately small for the LLVM 11 release, so we'd probably want to add clang-tidy config after the branch in a month, delaying it for one release cycle. How pressing is this?

[njames93]

Gotta say it's not hugely pressing.
The reason for it is clangd lets you specify some checks to run but it doesn't let you specify the options for those checks. Effectively forcing each project to require a .clang-tidy configuration file if you want to use checks where you require some configuration.
This isn't an issue on large scale established projects, but when starting out on small scale projects, it would be nice if clangd(tidy) was already set up how you like it without going through the need of setting up a .clang-tidy file.
Once D81949 lands it will also be useful on large scale projects that enforce certain tidy checks, but locally a developer may want extra configurable checks running in their editor.

Having said all of that your proposal does appear to do what this patch aims just in a much more user friendly way.

[njames93]

Small rebase

[njames93]

Abandoned in favour of the proposed clangd-config.

clang-tools-extra/clangd/test/clang-tidy-config.test

+# RUN: clangd -lit-test -clang-tidy-config="{CheckOptions: [{key: readability-identifier-naming.FunctionCase, value: camelBack}], Checks: '-*,readability-identifier-naming' }" < %s | FileCheck -strict-whitespace %s
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
+---
+{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"test:///foo.c","languageId":"c","text":"void BadName();"}}}
+#      CHECK:  "method": "textDocument/publishDiagnostics",
+# CHECK-NEXT:  "params": {
+# CHECK-NEXT:    "diagnostics": [
+# CHECK-NEXT:      {
+# CHECK-NEXT:        "code": "readability-identifier-naming",
+# CHECK-NEXT:        "message": "Invalid case style for function 'BadName' (fix available)",
+# CHECK-NEXT:        "range": {
+# CHECK-NEXT:          "end": {
+# CHECK-NEXT:            "character": 12,
+# CHECK-NEXT:            "line": 0
+# CHECK-NEXT:          },
+# CHECK-NEXT:          "start": {
+# CHECK-NEXT:            "character": 5,
+# CHECK-NEXT:            "line": 0
+# CHECK-NEXT:          }
+# CHECK-NEXT:        },
+# CHECK-NEXT:        "severity": 2,
+# CHECK-NEXT:        "source": "clang-tidy"
+# CHECK-NEXT:      }
+# CHECK-NEXT:    ],
+# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c",
+# CHECK-NEXT:    "version": 0
+# CHECK-NEXT:  }
+---
+{"jsonrpc":"2.0","id":2,"method":"sync","params":null}
+---
+{"jsonrpc":"2.0","method":"textDocument/didClose","params":{"textDocument":{"uri":"test:///foo.c"}}}
+#      CHECK:  "method": "textDocument/publishDiagnostics",
+# CHECK-NEXT:  "params": {
+# CHECK-NEXT:    "diagnostics": [],
+# CHECK-NEXT:    "uri": "file://{{.*}}/foo.c"
+# CHECK-NEXT:  }
+---
+{"jsonrpc":"2.0","id":5,"method":"shutdown"}
+---
+{"jsonrpc":"2.0","method":"exit"}

clang-tools-extra/clangd/tool/ClangdMain.cpp

 opt<std::string> ClangTidyChecks{
     "clang-tidy-checks",
     cat(Features),
     desc("List of clang-tidy checks to run (this will override "
          ".clang-tidy files). Only meaningful when -clang-tidy flag is on"),
     init(""),
 };
 
+opt<std::string> ClangTidyConfig{
+    "clang-tidy-config",
+    cat(Features),
+    desc("Specifies a YAML/JSON configuration for when running clang-tidy "
+         "checks (this will override clang-tidy files). Only meaningful when "
+         "-clang-tidy flag is on"),
+    init(""),
+};
+
 opt<CodeCompleteOptions::CodeCompletionParse> CodeCompletionParse{
     "completion-parse",
     cat(Features),
     desc("Whether the clang-parser is used for code-completion"),
     values(clEnumValN(CodeCompleteOptions::AlwaysParse, "always",
                       "Block until the parser can be used"),
            clEnumValN(CodeCompleteOptions::ParseIfReady, "auto",
                       "Use text-based completion if the parser "
#endif
   std::unique_ptr<tidy::ClangTidyOptionsProvider>
       ClangTidyOptProvider; /*GUARDED_BY(ClangTidyOptMu)*/
   if (EnableClangTidy) {
     auto EmptyDefaults = tidy::ClangTidyOptions::getDefaults();
     EmptyDefaults.Checks.reset(); // So we can tell if checks were ever set.
     tidy::ClangTidyOptions OverrideClangTidyOptions;
     if (!ClangTidyChecks.empty())
       OverrideClangTidyOptions.Checks = ClangTidyChecks;
+    if (ClangTidyConfig.empty()) {
       ClangTidyOptProvider = std::make_unique<tidy::FileOptionsProvider>(
           tidy::ClangTidyGlobalOptions(),
           /* Default */ EmptyDefaults,
-        /* Override */ OverrideClangTidyOptions, TFS.view(/*CWD=*/llvm::None));
+          /* Override */ OverrideClangTidyOptions,
+          TFS.view(/*CWD=*/llvm::None));
+    } else {
+      llvm::ErrorOr<tidy::ClangTidyOptions> ParsedConfig =
+          tidy::parseConfiguration(ClangTidyConfig);
+      if (!ParsedConfig) {
+        elog("Invalid -clang-tidy-config: {0}",
+             ParsedConfig.getError().message());
+        return 1;
+      }
+      ClangTidyOptProvider = std::make_unique<tidy::ConfigOptionsProvider>(
+          tidy::ClangTidyGlobalOptions(), EmptyDefaults, *ParsedConfig,
+          OverrideClangTidyOptions, TFS.view(/*CWD*/ llvm::None));
+    }
     Opts.GetClangTidyOptions = [&](llvm::vfs::FileSystem &,
                                    llvm::StringRef File) {
       // This function must be thread-safe and tidy option providers are not.
       tidy::ClangTidyOptions Opts;
       {
         std::lock_guard<std::mutex> Lock(ClangTidyOptMu);
         // FIXME: use the FS provided to the function.
         Opts = ClangTidyOptProvider->getOptions(File);