[clangd] Implement "textDocument/documentLink" protocol support

Summary:
This adds an implementation for the "textDocument/documentLink" LSP request.

It returns links for all `#include` directives to the resolved target files.

Fixes clangd/clangd#217.

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70872

Author: MForster

clang-tools-extra/clangd/ClangdLSPServer.cpp

@@ -566,6 +566,10 @@ void ClangdLSPServer::onInitialize(const InitializeParams &Params,
             {"declarationProvider", true},
             {"definitionProvider", true},
             {"documentHighlightProvider", true},
+            {"documentLinkProvider",
+             llvm::json::Object{
+                 {"resolveProvider", false},
+             }},
             {"hoverProvider", true},
             {"renameProvider", std::move(RenameProvider)},
             {"selectionRangeProvider", true},
@@ -1200,6 +1204,25 @@ void ClangdLSPServer::onSelectionRange(
       });
 }
 
+void ClangdLSPServer::onDocumentLink(
+    const DocumentLinkParams &Params,
+    Callback<std::vector<DocumentLink>> Reply) {
+
+  // TODO(forster): This currently resolves all targets eagerly. This is slow,
+  // because it blocks on the preamble/AST being built. We could respond to the
+  // request faster by using string matching or the lexer to find the includes
+  // and resolving the targets lazily.
+  Server->documentLinks(
+      Params.textDocument.uri.file(),
+      [Reply = std::move(Reply)](
+          llvm::Expected<std::vector<DocumentLink>> Links) mutable {
+        if (!Links) {
+          return Reply(Links.takeError());
+        }
+        return Reply(std::move(Links));
+      });
+}
+
 ClangdLSPServer::ClangdLSPServer(
     class Transport &Transp, const FileSystemProvider &FSProvider,
     const clangd::CodeCompleteOptions &CCOpts,
@@ -1243,6 +1266,7 @@ ClangdLSPServer::ClangdLSPServer(
   MsgHandler->bind("textDocument/typeHierarchy", &ClangdLSPServer::onTypeHierarchy);
   MsgHandler->bind("typeHierarchy/resolve", &ClangdLSPServer::onResolveTypeHierarchy);
   MsgHandler->bind("textDocument/selectionRange", &ClangdLSPServer::onSelectionRange);
+  MsgHandler->bind("textDocument/documentLink", &ClangdLSPServer::onDocumentLink);
   // clang-format on
 }
 

clang-tools-extra/clangd/ClangdLSPServer.h

@@ -111,6 +111,8 @@ class ClangdLSPServer : private DiagnosticsConsumer {
                     Callback<std::vector<SymbolDetails>>);
   void onSelectionRange(const SelectionRangeParams &,
                         Callback<std::vector<SelectionRange>>);
+  void onDocumentLink(const DocumentLinkParams &,
+                      Callback<std::vector<DocumentLink>>);
 
   std::vector<Fix> getFixes(StringRef File, const clangd::Diagnostic &D);
 

clang-tools-extra/clangd/ClangdServer.cpp

@@ -611,6 +611,17 @@ void ClangdServer::semanticRanges(PathRef File, Position Pos,
   WorkScheduler.runWithAST("SemanticRanges", File, std::move(Action));
 }
 
+void ClangdServer::documentLinks(PathRef File,
+                                 Callback<std::vector<DocumentLink>> CB) {
+  auto Action =
+      [CB = std::move(CB)](llvm::Expected<InputsAndAST> InpAST) mutable {
+        if (!InpAST)
+          return CB(InpAST.takeError());
+        CB(clangd::getDocumentLinks(InpAST->AST));
+      };
+  WorkScheduler.runWithAST("DocumentLinks", File, std::move(Action));
+}
+
 std::vector<std::pair<Path, std::size_t>>
 ClangdServer::getUsedBytesPerFile() const {
   return WorkScheduler.getUsedBytesPerFile();

clang-tools-extra/clangd/ClangdServer.h

@@ -287,6 +287,9 @@ class ClangdServer {
   void semanticRanges(PathRef File, Position Pos,
                       Callback<std::vector<Range>> CB);
 
+  /// Get all document links in a file.
+  void documentLinks(PathRef File, Callback<std::vector<DocumentLink>> CB);
+ 
   /// Returns estimated memory usage for each of the currently open files.
   /// The order of results is unspecified.
   /// Overall memory usage of clangd may be significantly more than reported

clang-tools-extra/clangd/Protocol.cpp

@@ -1087,5 +1087,18 @@ llvm::json::Value toJSON(const SelectionRange &Out) {
   }
   return llvm::json::Object{{"range", Out.range}};
 }
+
+bool fromJSON(const llvm::json::Value &Params, DocumentLinkParams &R) {
+  llvm::json::ObjectMapper O(Params);
+  return O && O.map("textDocument", R.textDocument);
+}
+
+llvm::json::Value toJSON(const DocumentLink &DocumentLink) {
+  return llvm::json::Object{
+      {"range", DocumentLink.range},
+      {"target", DocumentLink.target},
+  };
+}
+
 } // namespace clangd
 } // namespace clang

clang-tools-extra/clangd/Protocol.h

@@ -1250,6 +1250,39 @@ struct SelectionRange {
 };
 llvm::json::Value toJSON(const SelectionRange &);
 
+/// Parameters for the document link request.
+struct DocumentLinkParams {
+  /// The document to provide document links for.
+  TextDocumentIdentifier textDocument;
+};
+bool fromJSON(const llvm::json::Value &, DocumentLinkParams &);
+
+/// A range in a text document that links to an internal or external resource,
+/// like another text document or a web site.
+struct DocumentLink {
+  /// The range this link applies to.
+  Range range;
+
+  /// The uri this link points to. If missing a resolve request is sent later.
+  URIForFile target;
+
+  // TODO(forster): The following optional fields defined by the language
+  // server protocol are unsupported:
+  //
+  // data?: any - A data entry field that is preserved on a document link
+  //              between a DocumentLinkRequest and a
+  //              DocumentLinkResolveRequest.
+
+  friend bool operator==(const DocumentLink &LHS, const DocumentLink &RHS) {
+    return LHS.range == RHS.range && LHS.target == RHS.target;
+  }
+
+  friend bool operator!=(const DocumentLink &LHS, const DocumentLink &RHS) {
+    return !(LHS == RHS);
+  }
+};
+llvm::json::Value toJSON(const DocumentLink &DocumentLink);
+
 } // namespace clangd
 } // namespace clang
 

clang-tools-extra/clangd/XRefs.cpp

@@ -166,6 +166,26 @@ llvm::Optional<Location> makeLocation(ASTContext &AST, SourceLocation TokLoc,
 
 } // namespace
 
+std::vector<DocumentLink> getDocumentLinks(ParsedAST &AST) {
+  const auto &SM = AST.getSourceManager();
+  auto MainFilePath =
+      getCanonicalPath(SM.getFileEntryForID(SM.getMainFileID()), SM);
+  if (!MainFilePath) {
+    elog("Failed to get a path for the main file, so no links");
+    return {};
+  }
+
+  std::vector<DocumentLink> Result;
+  for (auto &Inc : AST.getIncludeStructure().MainFileIncludes) {
+    if (!Inc.Resolved.empty()) {
+      Result.push_back(DocumentLink(
+          {Inc.R, URIForFile::canonicalize(Inc.Resolved, *MainFilePath)}));
+    }
+  }
+
+  return Result;
+}
+
 std::vector<LocatedSymbol> locateSymbolAt(ParsedAST &AST, Position Pos,
                                           const SymbolIndex *Index) {
   const auto &SM = AST.getSourceManager();

clang-tools-extra/clangd/XRefs.h

@@ -49,6 +49,9 @@ llvm::raw_ostream &operator<<(llvm::raw_ostream &, const LocatedSymbol &);
 std::vector<LocatedSymbol> locateSymbolAt(ParsedAST &AST, Position Pos,
                                           const SymbolIndex *Index = nullptr);
 
+/// Get all document links
+std::vector<DocumentLink> getDocumentLinks(ParsedAST &AST);
+
 /// Returns highlights for all usages of a symbol at \p Pos.
 std::vector<DocumentHighlight> findDocumentHighlights(ParsedAST &AST,
                                                       Position Pos);

clang-tools-extra/clangd/test/document-link.test

@@ -0,0 +1,42 @@
+# RUN: clangd -lit-test < %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:///main.cpp","languageId":"cpp","version":1,"text":"#include <stdint.h>\n#include <stddef.h>"}}}
+---
+{"jsonrpc":"2.0","id":2,"method":"textDocument/documentLink","params":{"textDocument":{"uri":"test:///main.cpp"}}}
+#      CHECK:  "id": 2,
+# CHECK-NEXT:  "jsonrpc": "2.0",
+# CHECK-NEXT:  "result": [
+# CHECK-NEXT:    {
+# CHECK-NEXT:      "range": {
+# CHECK-NEXT:        "end": {
+# CHECK-NEXT:          "character": 19,
+# CHECK-NEXT:          "line": 0
+# CHECK-NEXT:        },
+# CHECK-NEXT:        "start": {
+# CHECK-NEXT:          "character": 9,
+# CHECK-NEXT:          "line": 0
+# CHECK-NEXT:        }
+# CHECK-NEXT:      },
+# CHECK-NEXT:      "target": "file://{{.*}}/stdint.h"
+# CHECK-NEXT:    },
+# CHECK-NEXT:    {
+# CHECK-NEXT:      "range": {
+# CHECK-NEXT:        "end": {
+# CHECK-NEXT:          "character": 19,
+# CHECK-NEXT:          "line": 1
+# CHECK-NEXT:        },
+# CHECK-NEXT:        "start": {
+# CHECK-NEXT:          "character": 9,
+# CHECK-NEXT:          "line": 1
+# CHECK-NEXT:        }
+# CHECK-NEXT:      },
+# CHECK-NEXT:      "target": "file://{{.*}}/stddef.h"
+# CHECK-NEXT:    }
+# CHECK-NEXT:  ]
+# CHECK-NEXT:}
+
+---
+{"jsonrpc":"2.0","id":3,"method":"shutdown"}
+---
+{"jsonrpc":"2.0","method":"exit"}

clang-tools-extra/clangd/test/initialize-params.test

@@ -18,6 +18,9 @@
 # CHECK-NEXT:      "definitionProvider": true,
 # CHECK-NEXT:      "documentFormattingProvider": true,
 # CHECK-NEXT:      "documentHighlightProvider": true,
+# CHECK-NEXT:      "documentLinkProvider": {
+# CHECK-NEXT:        "resolveProvider": false
+# CHECK-NEXT:      }
 # CHECK-NEXT:      "documentOnTypeFormattingProvider": {
 # CHECK-NEXT:        "firstTriggerCharacter": "\n",
 # CHECK-NEXT:        "moreTriggerCharacter": []