1 //===--- JSONTransport.cpp - sending and receiving LSP messages over JSON -===//
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 #include "Logger.h"
9 #include "Protocol.h" // For LSPError
10 #include "Transport.h"
11 #include "llvm/Support/Errno.h"
12 
13 namespace clang {
14 namespace clangd {
15 namespace {
16 
17 llvm::json::Object encodeError(llvm::Error E) {
18   std::string Message;
19   ErrorCode Code = ErrorCode::UnknownErrorCode;
20   if (llvm::Error Unhandled = llvm::handleErrors(
21           std::move(E), [&](const LSPError &L) -> llvm::Error {
22             Message = L.Message;
23             Code = L.Code;
24             return llvm::Error::success();
25           }))
26     Message = llvm::toString(std::move(Unhandled));
27 
28   return llvm::json::Object{
29       {"message", std::move(Message)},
30       {"code", int64_t(Code)},
31   };
32 }
33 
34 llvm::Error decodeError(const llvm::json::Object &O) {
35   std::string Msg = O.getString("message").getValueOr("Unspecified error");
36   if (auto Code = O.getInteger("code"))
37     return llvm::make_error<LSPError>(std::move(Msg), ErrorCode(*Code));
38   return llvm::make_error<llvm::StringError>(std::move(Msg),
39                                              llvm::inconvertibleErrorCode());
40 }
41 
42 class JSONTransport : public Transport {
43 public:
44   JSONTransport(std::FILE *In, llvm::raw_ostream &Out,
45                 llvm::raw_ostream *InMirror, bool Pretty, JSONStreamStyle Style)
46       : In(In), Out(Out), InMirror(InMirror ? *InMirror : llvm::nulls()),
47         Pretty(Pretty), Style(Style) {}
48 
49   void notify(llvm::StringRef Method, llvm::json::Value Params) override {
50     sendMessage(llvm::json::Object{
51         {"jsonrpc", "2.0"},
52         {"method", Method},
53         {"params", std::move(Params)},
54     });
55   }
56   void call(llvm::StringRef Method, llvm::json::Value Params,
57             llvm::json::Value ID) override {
58     sendMessage(llvm::json::Object{
59         {"jsonrpc", "2.0"},
60         {"id", std::move(ID)},
61         {"method", Method},
62         {"params", std::move(Params)},
63     });
64   }
65   void reply(llvm::json::Value ID,
66              llvm::Expected<llvm::json::Value> Result) override {
67     if (Result) {
68       sendMessage(llvm::json::Object{
69           {"jsonrpc", "2.0"},
70           {"id", std::move(ID)},
71           {"result", std::move(*Result)},
72       });
73     } else {
74       sendMessage(llvm::json::Object{
75           {"jsonrpc", "2.0"},
76           {"id", std::move(ID)},
77           {"error", encodeError(Result.takeError())},
78       });
79     }
80   }
81 
82   llvm::Error loop(MessageHandler &Handler) override {
83     while (!feof(In)) {
84       if (ferror(In))
85         return llvm::errorCodeToError(
86             std::error_code(errno, std::system_category()));
87       if (auto JSON = readRawMessage()) {
88         if (auto Doc = llvm::json::parse(*JSON)) {
89           vlog(Pretty ? "<<< {0:2}\n" : "<<< {0}\n", *Doc);
90           if (!handleMessage(std::move(*Doc), Handler))
91             return llvm::Error::success(); // we saw the "exit" notification.
92         } else {
93           // Parse error. Log the raw message.
94           vlog("<<< {0}\n", *JSON);
95           elog("JSON parse error: {0}", llvm::toString(Doc.takeError()));
96         }
97       }
98     }
99     return llvm::errorCodeToError(std::make_error_code(std::errc::io_error));
100   }
101 
102 private:
103   // Dispatches incoming message to Handler onNotify/onCall/onReply.
104   bool handleMessage(llvm::json::Value Message, MessageHandler &Handler);
105   // Writes outgoing message to Out stream.
106   void sendMessage(llvm::json::Value Message) {
107     std::string S;
108     llvm::raw_string_ostream OS(S);
109     OS << llvm::formatv(Pretty ? "{0:2}" : "{0}", Message);
110     OS.flush();
111     Out << "Content-Length: " << S.size() << "\r\n\r\n" << S;
112     Out.flush();
113     vlog(">>> {0}\n", S);
114   }
115 
116   // Read raw string messages from input stream.
117   llvm::Optional<std::string> readRawMessage() {
118     return Style == JSONStreamStyle::Delimited ? readDelimitedMessage()
119                                                : readStandardMessage();
120   }
121   llvm::Optional<std::string> readDelimitedMessage();
122   llvm::Optional<std::string> readStandardMessage();
123 
124   std::FILE *In;
125   llvm::raw_ostream &Out;
126   llvm::raw_ostream &InMirror;
127   bool Pretty;
128   JSONStreamStyle Style;
129 };
130 
131 bool JSONTransport::handleMessage(llvm::json::Value Message,
132                                   MessageHandler &Handler) {
133   // Message must be an object with "jsonrpc":"2.0".
134   auto *Object = Message.getAsObject();
135   if (!Object ||
136       Object->getString("jsonrpc") != llvm::Optional<llvm::StringRef>("2.0")) {
137     elog("Not a JSON-RPC 2.0 message: {0:2}", Message);
138     return false;
139   }
140   // ID may be any JSON value. If absent, this is a notification.
141   llvm::Optional<llvm::json::Value> ID;
142   if (auto *I = Object->get("id"))
143     ID = std::move(*I);
144   auto Method = Object->getString("method");
145   if (!Method) { // This is a response.
146     if (!ID) {
147       elog("No method and no response ID: {0:2}", Message);
148       return false;
149     }
150     if (auto *Err = Object->getObject("error"))
151       return Handler.onReply(std::move(*ID), decodeError(*Err));
152     // Result should be given, use null if not.
153     llvm::json::Value Result = nullptr;
154     if (auto *R = Object->get("result"))
155       Result = std::move(*R);
156     return Handler.onReply(std::move(*ID), std::move(Result));
157   }
158   // Params should be given, use null if not.
159   llvm::json::Value Params = nullptr;
160   if (auto *P = Object->get("params"))
161     Params = std::move(*P);
162 
163   if (ID)
164     return Handler.onCall(*Method, std::move(Params), std::move(*ID));
165   else
166     return Handler.onNotify(*Method, std::move(Params));
167 }
168 
169 // Tries to read a line up to and including \n.
170 // If failing, feof() or ferror() will be set.
171 bool readLine(std::FILE *In, std::string &Out) {
172   static constexpr int BufSize = 1024;
173   size_t Size = 0;
174   Out.clear();
175   for (;;) {
176     Out.resize(Size + BufSize);
177     // Handle EINTR which is sent when a debugger attaches on some platforms.
178     if (!llvm::sys::RetryAfterSignal(nullptr, ::fgets, &Out[Size], BufSize, In))
179       return false;
180     clearerr(In);
181     // If the line contained null bytes, anything after it (including \n) will
182     // be ignored. Fortunately this is not a legal header or JSON.
183     size_t Read = std::strlen(&Out[Size]);
184     if (Read > 0 && Out[Size + Read - 1] == '\n') {
185       Out.resize(Size + Read);
186       return true;
187     }
188     Size += Read;
189   }
190 }
191 
192 // Returns None when:
193 //  - ferror() or feof() are set.
194 //  - Content-Length is missing or empty (protocol error)
195 llvm::Optional<std::string> JSONTransport::readStandardMessage() {
196   // A Language Server Protocol message starts with a set of HTTP headers,
197   // delimited  by \r\n, and terminated by an empty line (\r\n).
198   unsigned long long ContentLength = 0;
199   std::string Line;
200   while (true) {
201     if (feof(In) || ferror(In) || !readLine(In, Line))
202       return llvm::None;
203     InMirror << Line;
204 
205     llvm::StringRef LineRef(Line);
206 
207     // We allow comments in headers. Technically this isn't part
208 
209     // of the LSP specification, but makes writing tests easier.
210     if (LineRef.startswith("#"))
211       continue;
212 
213     // Content-Length is a mandatory header, and the only one we handle.
214     if (LineRef.consume_front("Content-Length: ")) {
215       if (ContentLength != 0) {
216         elog("Warning: Duplicate Content-Length header received. "
217              "The previous value for this message ({0}) was ignored.",
218              ContentLength);
219       }
220       llvm::getAsUnsignedInteger(LineRef.trim(), 0, ContentLength);
221       continue;
222     } else if (!LineRef.trim().empty()) {
223       // It's another header, ignore it.
224       continue;
225     } else {
226       // An empty line indicates the end of headers.
227       // Go ahead and read the JSON.
228       break;
229     }
230   }
231 
232   // The fuzzer likes crashing us by sending "Content-Length: 9999999999999999"
233   if (ContentLength > 1 << 30) { // 1024M
234     elog("Refusing to read message with long Content-Length: {0}. "
235          "Expect protocol errors",
236          ContentLength);
237     return llvm::None;
238   }
239   if (ContentLength == 0) {
240     log("Warning: Missing Content-Length header, or zero-length message.");
241     return llvm::None;
242   }
243 
244   std::string JSON(ContentLength, '\0');
245   for (size_t Pos = 0, Read; Pos < ContentLength; Pos += Read) {
246     // Handle EINTR which is sent when a debugger attaches on some platforms.
247     Read = llvm::sys::RetryAfterSignal(0u, ::fread, &JSON[Pos], 1,
248                                        ContentLength - Pos, In);
249     if (Read == 0) {
250       elog("Input was aborted. Read only {0} bytes of expected {1}.", Pos,
251            ContentLength);
252       return llvm::None;
253     }
254     InMirror << llvm::StringRef(&JSON[Pos], Read);
255     clearerr(In); // If we're done, the error was transient. If we're not done,
256                   // either it was transient or we'll see it again on retry.
257     Pos += Read;
258   }
259   return std::move(JSON);
260 }
261 
262 // For lit tests we support a simplified syntax:
263 // - messages are delimited by '---' on a line by itself
264 // - lines starting with # are ignored.
265 // This is a testing path, so favor simplicity over performance here.
266 // When returning None, feof() or ferror() will be set.
267 llvm::Optional<std::string> JSONTransport::readDelimitedMessage() {
268   std::string JSON;
269   std::string Line;
270   while (readLine(In, Line)) {
271     InMirror << Line;
272     auto LineRef = llvm::StringRef(Line).trim();
273     if (LineRef.startswith("#")) // comment
274       continue;
275 
276     // found a delimiter
277     if (LineRef.rtrim() == "---")
278       break;
279 
280     JSON += Line;
281   }
282 
283   if (ferror(In)) {
284     elog("Input error while reading message!");
285     return llvm::None;
286   }
287   return std::move(JSON); // Including at EOF
288 }
289 
290 } // namespace
291 
292 std::unique_ptr<Transport> newJSONTransport(std::FILE *In,
293                                             llvm::raw_ostream &Out,
294                                             llvm::raw_ostream *InMirror,
295                                             bool Pretty,
296                                             JSONStreamStyle Style) {
297   return std::make_unique<JSONTransport>(In, Out, InMirror, Pretty, Style);
298 }
299 
300 } // namespace clangd
301 } // namespace clang
302