[clangd] Propagate main context into ClangdServer

[kadircet]

Summary

Currently clangd initializes the ClangdServer lazily during
onInitialize request, and it results in propagation of caller's context rather
than the main context created ClangdLSPServer.

This patch changes the logic to store main context that created ClangdLSPServer
and pass it onto to ClangdServer and other objects like CDBs.

[merge_guards_bot]

Bulid results are available at http://results.llvm-merge-guard.org/Phabricator-35

See http://jenkins.llvm-merge-guard.org/job/Phabricator/35/ for more details.

[sammccall]

clang-tools-extra/clangd/ClangdLSPServer.cpp

463

As discussed offline: I think it'd be clearer to put this in a small block around the construction of clangd server. (Then we can avoid some ofthe Optional bits too)

[sammccall]

Otherwise LG

[kadircet]

• Move context swapping next to server creation

[merge_guards_bot]

Bulid results are available at http://results.llvm-merge-guard.org/Phabricator-39

See http://jenkins.llvm-merge-guard.org/job/Phabricator/39/ for more details.

[ilya-biryukov]

clang-tools-extra/clangd/ClangdLSPServer.h

135

NIT: Use tripple slash comments

clang-tools-extra/clangd/ClangdLSPServer.h

 //===--- ClangdLSPServer.h - LSP server --------------------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_CLANGDLSPSERVER_H
 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_CLANGDLSPSERVER_H
 
 #include "ClangdServer.h"
+#include "Context.h"
 #include "DraftStore.h"
 #include "Features.inc"
 #include "FindSymbols.h"
 #include "GlobalCompilationDatabase.h"
 #include "Path.h"
 #include "Protocol.h"
 #include "Transport.h"
 #include "clang/Tooling/Core/Replacement.h"
private:
 
   /// Sends a "publishSemanticHighlighting" notification to the LSP client.
   void publishSemanticHighlighting(SemanticHighlightingParams Params);
 
   /// Sends a "publishDiagnostics" notification to the LSP client.
   void publishDiagnostics(const URIForFile &File,
                           std::vector<clangd::Diagnostic> Diagnostics);
 
+  // Since initialization of CDBs and ClangdServer is done lazily, the following
+  // context captures the one used while creating ClangdLSPServer and passes it
+  // to above mentioned object instances to make sure they share the same state.
+  Context BackgroundContext;
+
   /// Used to indicate that the 'shutdown' request was received from the
   /// Language Server client.
   bool ShutdownRequestReceived = false;
 
   /// Used to indicate the ClangdLSPServer is being destroyed.
   std::atomic<bool> IsBeingDestroyed = {false};
 
   std::mutex FixItsMutex;

clang-tools-extra/clangd/ClangdLSPServer.cpp

 //===--- ClangdLSPServer.cpp - LSP server ------------------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "ClangdLSPServer.h"
+#include "Context.h"
 #include "Diagnostics.h"
 #include "DraftStore.h"
 #include "FormattedString.h"
 #include "GlobalCompilationDatabase.h"
 #include "Protocol.h"
 #include "SemanticHighlighting.h"
 #include "SourceCode.h"
 #include "Trace.h"

 void ClangdLSPServer::notify(llvm::StringRef Method, llvm::json::Value Params) {
   log("--> {0}", Method);
   std::lock_guard<std::mutex> Lock(TranspWriter);
   Transp.notify(Method, std::move(Params));
 }
 
 void ClangdLSPServer::onInitialize(const InitializeParams &Params,
                                    Callback<llvm::json::Value> Reply) {
+  // Switch caller's context with LSPServer's background context. Since we
+  // rather want to propagate information from LSPServer's context into the
+  // Server, CDB, etc.
+  llvm::Optional<WithContext> MainContext;
+  MainContext.emplace(BackgroundContext.clone());
   // Determine character encoding first as it affects constructed ClangdServer.
   if (Params.capabilities.offsetEncoding && !NegotiatedOffsetEncoding) {
     NegotiatedOffsetEncoding = OffsetEncoding::UTF16; // fallback
     for (OffsetEncoding Supported : *Params.capabilities.offsetEncoding)
       if (Supported != OffsetEncoding::UnsupportedEncoding) {
         NegotiatedOffsetEncoding = Supported;
         break;
       }
llvm::json::Object Result{
         }}}};
   if (NegotiatedOffsetEncoding)
     Result["offsetEncoding"] = *NegotiatedOffsetEncoding;
   if (Params.capabilities.SemanticHighlighting)
     Result.getObject("capabilities")
         ->insert(
             {"semanticHighlighting",
              llvm::json::Object{{"scopes", buildHighlightScopeLookupTable()}}});
+  // Restore caller's context.
+  MainContext.reset();
   Reply(std::move(Result));
 }
 
 void ClangdLSPServer::onShutdown(const ShutdownParams &Params,
                                  Callback<std::nullptr_t> Reply) {
   // Do essentially nothing, just say we're ready to exit.
   ShutdownRequestReceived = true;
   Reply(nullptr);

 }
 
 ClangdLSPServer::ClangdLSPServer(
     class Transport &Transp, const FileSystemProvider &FSProvider,
     const clangd::CodeCompleteOptions &CCOpts,
     llvm::Optional<Path> CompileCommandsDir, bool UseDirBasedCDB,
     llvm::Optional<OffsetEncoding> ForcedOffsetEncoding,
     const ClangdServer::Options &Opts)
-    : Transp(Transp), MsgHandler(new MessageHandler(*this)),
-      FSProvider(FSProvider), CCOpts(CCOpts),
-      SupportedSymbolKinds(defaultSymbolKinds()),
+    : BackgroundContext(Context::current().clone()), Transp(Transp),
+      MsgHandler(new MessageHandler(*this)), FSProvider(FSProvider),
+      CCOpts(CCOpts), SupportedSymbolKinds(defaultSymbolKinds()),
       SupportedCompletionItemKinds(defaultCompletionItemKinds()),
       UseDirBasedCDB(UseDirBasedCDB),
       CompileCommandsDir(std::move(CompileCommandsDir)), ClangdServerOpts(Opts),
       NegotiatedOffsetEncoding(ForcedOffsetEncoding) {
   // clang-format off
   MsgHandler->bind("initialize", &ClangdLSPServer::onInitialize);
   MsgHandler->bind("shutdown", &ClangdLSPServer::onShutdown);
   MsgHandler->bind("sync", &ClangdLSPServer::onSync);