1 //===--- Transport.h - sending and receiving LSP messages -------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // The language server protocol is usually implemented by writing messages as 10 // JSON-RPC over the stdin/stdout of a subprocess. However other communications 11 // mechanisms are possible, such as XPC on mac. 12 // 13 // The Transport interface allows the mechanism to be replaced, and the JSONRPC 14 // Transport is the standard implementation. 15 // 16 //===----------------------------------------------------------------------===// 17 18 #ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_TRANSPORT_H_ 19 #define LLVM_CLANG_TOOLS_EXTRA_CLANGD_TRANSPORT_H_ 20 21 #include "llvm/ADT/StringRef.h" 22 #include "llvm/Support/JSON.h" 23 #include "llvm/Support/raw_ostream.h" 24 25 namespace clang { 26 namespace clangd { 27 28 // A transport is responsible for maintaining the connection to a client 29 // application, and reading/writing structured messages to it. 30 // 31 // Transports have limited thread safety requirements: 32 // - messages will not be sent concurrently 33 // - messages MAY be sent while loop() is reading, or its callback is active 34 class Transport { 35 public: 36 virtual ~Transport() = default; 37 38 // Called by Clangd to send messages to the client. 39 virtual void notify(llvm::StringRef Method, llvm::json::Value Params) = 0; 40 virtual void call(llvm::StringRef Method, llvm::json::Value Params, 41 llvm::json::Value ID) = 0; 42 virtual void reply(llvm::json::Value ID, 43 llvm::Expected<llvm::json::Value> Result) = 0; 44 45 // Implemented by Clangd to handle incoming messages. (See loop() below). 46 class MessageHandler { 47 public: 48 virtual ~MessageHandler() = default; 49 // Handler returns true to keep processing messages, or false to shut down. 50 virtual bool onNotify(llvm::StringRef Method, llvm::json::Value) = 0; 51 virtual bool onCall(llvm::StringRef Method, llvm::json::Value Params, 52 llvm::json::Value ID) = 0; 53 virtual bool onReply(llvm::json::Value ID, 54 llvm::Expected<llvm::json::Value> Result) = 0; 55 }; 56 // Called by Clangd to receive messages from the client. 57 // The transport should in turn invoke the handler to process messages. 58 // If handler returns false, the transport should immediately exit the loop. 59 // (This is used to implement the `exit` notification). 60 // Otherwise, it returns an error when the transport becomes unusable. 61 virtual llvm::Error loop(MessageHandler &) = 0; 62 }; 63 64 // Controls the way JSON-RPC messages are encoded (both input and output). 65 enum JSONStreamStyle { 66 // Encoding per the LSP specification, with mandatory Content-Length header. 67 Standard, 68 // Messages are delimited by a '---' line. Comment lines start with #. 69 Delimited 70 }; 71 72 // Returns a Transport that speaks JSON-RPC over a pair of streams. 73 // The input stream must be opened in binary mode. 74 // If InMirror is set, data read will be echoed to it. 75 // 76 // The use of C-style std::FILE* input deserves some explanation. 77 // Previously, std::istream was used. When a debugger attached on MacOS, the 78 // process received EINTR, the stream went bad, and clangd exited. 79 // A retry-on-EINTR loop around reads solved this problem, but caused clangd to 80 // sometimes hang rather than exit on other OSes. The interaction between 81 // istreams and signals isn't well-specified, so it's hard to get this right. 82 // The C APIs seem to be clearer in this respect. 83 std::unique_ptr<Transport> 84 newJSONTransport(std::FILE *In, llvm::raw_ostream &Out, 85 llvm::raw_ostream *InMirror, bool Pretty, 86 JSONStreamStyle = JSONStreamStyle::Standard); 87 88 #if CLANGD_BUILD_XPC 89 // Returns a Transport for macOS based on XPC. 90 // Clangd with this transport is meant to be run as bundled XPC service. 91 std::unique_ptr<Transport> newXPCTransport(); 92 #endif 93 94 } // namespace clangd 95 } // namespace clang 96 97 #endif 98