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 "Feature.h"
22#include "llvm/ADT/StringRef.h"
23#include "llvm/Support/JSON.h"
24#include "llvm/Support/raw_ostream.h"
25
26namespace clang {
27namespace clangd {
28
29// A transport is responsible for maintaining the connection to a client
30// application, and reading/writing structured messages to it.
31//
32// Transports have limited thread safety requirements:
33// - messages will not be sent concurrently
34// - messages MAY be sent while loop() is reading, or its callback is active
35class Transport {
36public:
37 virtual ~Transport() = default;
38
39 // Called by Clangd to send messages to the client.
40 virtual void notify(llvm::StringRef Method, llvm::json::Value Params) = 0;
41 virtual void call(llvm::StringRef Method, llvm::json::Value Params,
42 llvm::json::Value ID) = 0;
43 virtual void reply(llvm::json::Value ID,
44 llvm::Expected<llvm::json::Value> Result) = 0;
45
46 // Implemented by Clangd to handle incoming messages. (See loop() below).
47 class MessageHandler {
48 public:
49 virtual ~MessageHandler() = default;
50 // Handler returns true to keep processing messages, or false to shut down.
51 virtual bool onNotify(llvm::StringRef Method, llvm::json::Value) = 0;
52 virtual bool onCall(llvm::StringRef Method, llvm::json::Value Params,
53 llvm::json::Value ID) = 0;
54 virtual bool onReply(llvm::json::Value ID,
55 llvm::Expected<llvm::json::Value> Result) = 0;
56 };
57 // Called by Clangd to receive messages from the client.
58 // The transport should in turn invoke the handler to process messages.
59 // If handler returns false, the transport should immediately exit the loop.
60 // (This is used to implement the `exit` notification).
61 // Otherwise, it returns an error when the transport becomes unusable.
62 virtual llvm::Error loop(MessageHandler &) = 0;
63};
64
65// Controls the way JSON-RPC messages are encoded (both input and output).
66enum JSONStreamStyle {
67 // Encoding per the LSP specification, with mandatory Content-Length header.
68 Standard,
69 // Messages are delimited by a '---' line. Comment lines start with #.
70 Delimited
71};
72
73// Returns a Transport that speaks JSON-RPC over a pair of streams.
74// The input stream must be opened in binary mode.
75// If InMirror is set, data read will be echoed to it.
76//
77// The use of C-style std::FILE* input deserves some explanation.
78// Previously, std::istream was used. When a debugger attached on MacOS, the
79// process received EINTR, the stream went bad, and clangd exited.
80// A retry-on-EINTR loop around reads solved this problem, but caused clangd to
81// sometimes hang rather than exit on other OSes. The interaction between
82// istreams and signals isn't well-specified, so it's hard to get this right.
83// The C APIs seem to be clearer in this respect.
84std::unique_ptr<Transport>
85newJSONTransport(std::FILE *In, llvm::raw_ostream &Out,
86 llvm::raw_ostream *InMirror, bool Pretty,
87 JSONStreamStyle = JSONStreamStyle::Standard);
88
89#if CLANGD_BUILD_XPC
90// Returns a Transport for macOS based on XPC.
91// Clangd with this transport is meant to be run as bundled XPC service.
92std::unique_ptr<Transport> newXPCTransport();
93#endif
94
95} // namespace clangd
96} // namespace clang
97
98#endif
99

source code of clang-tools-extra/clangd/Transport.h