[clangd] Fix LineFoldingOnly flag is not propagated correctly to ClangdServer.

[hokein]

Summary

The Opts.LineFoldingOnly must be set before the clangdServer
construction, otherwise this flag is always false when using clangd in VSCode.

[usaxena95]

Thanks. Sorry I missed this.

clang-tools-extra/clangd/ClangdLSPServer.cpp

487–497

I think we should do this after the Opts has been fully set to avoid the confusion

[hokein]

address comment: create the ClangdServer when Opts is fully initialized.

clang-tools-extra/clangd/ClangdLSPServer.cpp

void ClangdLSPServer::onInitialize(const InitializeParams &Params,
   }
 
   if (Params.capabilities.TheiaSemanticHighlighting &&
       !Params.capabilities.SemanticTokens) {
     elog("Client requested legacy semanticHighlights notification, which is "
          "no longer supported. Migrate to standard semanticTokens request");
   }
 
+  // Must be initialized before creating a ClangdServer object!
+  Opts.LineFoldingOnly = Params.capabilities.LineFoldingOnly;
+
   if (Params.rootUri && *Params.rootUri)
     Opts.WorkspaceRoot = std::string(Params.rootUri->file());
   else if (Params.rootPath && !Params.rootPath->empty())
     Opts.WorkspaceRoot = *Params.rootPath;
   if (Server)
     return Reply(llvm::make_error<LSPError>("server already initialized",
                                             ErrorCode::InvalidRequest));
   if (Opts.UseDirBasedCDB) {
     DirectoryBasedGlobalCompilationDatabase::Options CDBOpts(TFS);
     if (const auto &Dir = Params.initializationOptions.compilationDatabasePath)
       CDBOpts.CompileCommandsDir = Dir;
     CDBOpts.ContextProvider = Opts.ContextProvider;
     BaseCDB =
         std::make_unique<DirectoryBasedGlobalCompilationDatabase>(CDBOpts);
     BaseCDB = getQueryDriverDatabase(llvm::makeArrayRef(Opts.QueryDriverGlobs),
                                      std::move(BaseCDB));
   }
   auto Mangler = CommandMangler::detect();
   if (Opts.ResourceDir)
     Mangler.ResourceDir = *Opts.ResourceDir;
   CDB.emplace(BaseCDB.get(), Params.initializationOptions.fallbackFlags,
               tooling::ArgumentsAdjuster(std::move(Mangler)));
   {
     // 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.
     WithContext MainContext(BackgroundContext.clone());
     llvm::Optional<WithContextValue> WithOffsetEncoding;
     if (Opts.Encoding)
       WithOffsetEncoding.emplace(kCurrentOffsetEncoding, *Opts.Encoding);
     Server.emplace(*CDB, TFS, Opts,
                    static_cast<ClangdServer::Callbacks *>(this));
   }
 
   Opts.CodeComplete.EnableSnippets = Params.capabilities.CompletionSnippets;
   Opts.CodeComplete.IncludeFixIts = Params.capabilities.CompletionFixes;
   if (!Opts.CodeComplete.BundleOverloads)
     Opts.CodeComplete.BundleOverloads = Params.capabilities.HasSignatureHelp;
   Opts.CodeComplete.DocumentationFormat =
       Params.capabilities.CompletionDocumentationFormat;
   Opts.SignatureHelpDocumentationFormat =
       Params.capabilities.SignatureHelpDocumentationFormat;
   DiagOpts.EmbedFixesInDiagnostics = Params.capabilities.DiagnosticFixes;
   DiagOpts.SendDiagnosticCategory = Params.capabilities.DiagnosticCategory;
   DiagOpts.EmitRelatedLocations =
       Params.capabilities.DiagnosticRelatedInformation;
   if (Params.capabilities.WorkspaceSymbolKinds)
     SupportedSymbolKinds |= *Params.capabilities.WorkspaceSymbolKinds;
   if (Params.capabilities.CompletionItemKinds)
     SupportedCompletionItemKinds |= *Params.capabilities.CompletionItemKinds;
   SupportsCodeAction = Params.capabilities.CodeActionStructure;
   SupportsHierarchicalDocumentSymbol =
       Params.capabilities.HierarchicalDocumentSymbol;
   SupportFileStatus = Params.initializationOptions.FileStatus;
   HoverContentFormat = Params.capabilities.HoverContentFormat;
-  Opts.LineFoldingOnly = Params.capabilities.LineFoldingOnly;
   SupportsOffsetsInSignatureHelp = Params.capabilities.OffsetsInSignatureHelp;
   if (Params.capabilities.WorkDoneProgress)
     BackgroundIndexProgressState = BackgroundIndexProgress::Empty;
   BackgroundIndexSkipCreate = Params.capabilities.ImplicitProgressCreation;
   Opts.ImplicitCancellation = !Params.capabilities.CancelsStaleRequests;
 
   llvm::json::Object ServerCaps{
       {"textDocumentSync",

clang-tools-extra/clangd/test/folding-range.test

+# RUN: clangd -lit-test < %s | FileCheck -strict-whitespace %s
+void f() {
+
+}
+---
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{"textDocument": {"foldingRange": {"lineFoldingOnly": true}}},"trace":"off"}}
+---
+{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"languageId":"cpp","text":"void f() {\n\n}\n","uri":"test:///foo.cpp","version":1}}}
+---
+{"id":1,"jsonrpc":"2.0","method":"textDocument/foldingRange","params":{"textDocument":{"uri":"test:///foo.cpp"}}}
+# CHECK:      "id": 1,
+# CHECK-NEXT: "jsonrpc": "2.0",
+# CHECK-NEXT: "result": [
+# CHECK-NEXT:   {
+# CHECK-NEXT:     "endLine": 1,
+# CHECK-NEXT:     "kind": "region", 
+# CHECK-NEXT:     "startCharacter": 10,
+# CHECK-NEXT:     "startLine": 0
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+---
+{"jsonrpc":"2.0","id":5,"method":"shutdown"}
+---
+{"jsonrpc":"2.0","method":"exit"}