clang-tools-extra/clangd/JSONTransport.cpp

   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 "Protocol.h" // For LSPError
   9 #include "Transport.h"
  10 #include "support/Cancellation.h"
  11 #include "support/Logger.h"
  12 #include "support/Shutdown.h"
  13 #include "support/ThreadCrashReporter.h"
  14 #include "llvm/ADT/SmallString.h"
  15 #include "llvm/Support/Error.h"
  16 #include <optional>
  17 #include <system_error>
  18
  19 namespace clang {
  20 namespace clangd {
  21 namespace {
  22
  23 llvm::json::Object encodeError(llvm::Error E) {
  24   std::string Message;
  25   ErrorCode Code = ErrorCode::UnknownErrorCode;
  26   // FIXME: encode cancellation errors using RequestCancelled or ContentModified
  27   // as appropriate.
  28   if (llvm::Error Unhandled = llvm::handleErrors(
  29           std::move(E),
  30           [&](const CancelledError &C) -> llvm::Error {
  31             switch (C.Reason) {
  32             case static_cast<int>(ErrorCode::ContentModified):
  33               Code = ErrorCode::ContentModified;
  34               Message = "Request cancelled because the document was modified";
  35               break;
  36             default:
  37               Code = ErrorCode::RequestCancelled;
  38               Message = "Request cancelled";
  39               break;
  40             }
  41             return llvm::Error::success();
  42           },
  43           [&](const LSPError &L) -> llvm::Error {
  44             Message = L.Message;
  45             Code = L.Code;
  46             return llvm::Error::success();
  47           }))
  48     Message = llvm::toString(std::move(Unhandled));
  49
  50   return llvm::json::Object{
  51       {"message", std::move(Message)},
  52       {"code", int64_t(Code)},
  53   };
  54 }
  55
  56 llvm::Error decodeError(const llvm::json::Object &O) {
  57   llvm::StringRef Msg = O.getString("message").value_or("Unspecified error");
  58   if (auto Code = O.getInteger("code"))
  59     return llvm::make_error<LSPError>(Msg.str(), ErrorCode(*Code));
  60   return error(Msg.str());
  61 }
  62
  63 class JSONTransport : public Transport {
  64 public:
  65   JSONTransport(std::FILE *In, llvm::raw_ostream &Out,
  66                 llvm::raw_ostream *InMirror, bool Pretty, JSONStreamStyle Style)
  67       : In(In), Out(Out), InMirror(InMirror ? *InMirror : llvm::nulls()),
  68         Pretty(Pretty), Style(Style) {}
  69
  70   void notify(llvm::StringRef Method, llvm::json::Value Params) override {
  71     sendMessage(llvm::json::Object{
  72         {"jsonrpc", "2.0"},
  73         {"method", Method},
  74         {"params", std::move(Params)},
  75     });
  76   }
  77   void call(llvm::StringRef Method, llvm::json::Value Params,
  78             llvm::json::Value ID) override {
  79     sendMessage(llvm::json::Object{
  80         {"jsonrpc", "2.0"},
  81         {"id", std::move(ID)},
  82         {"method", Method},
  83         {"params", std::move(Params)},
  84     });
  85   }
  86   void reply(llvm::json::Value ID,
  87              llvm::Expected<llvm::json::Value> Result) override {
  88     if (Result) {
  89       sendMessage(llvm::json::Object{
  90           {"jsonrpc", "2.0"},
  91           {"id", std::move(ID)},
  92           {"result", std::move(*Result)},
  93       });
  94     } else {
  95       sendMessage(llvm::json::Object{
  96           {"jsonrpc", "2.0"},
  97           {"id", std::move(ID)},
  98           {"error", encodeError(Result.takeError())},
  99       });
 100     }
 101   }
 102
 103   llvm::Error loop(MessageHandler &Handler) override {
 104     std::string JSON; // Messages may be large, reuse same big buffer.
 105     while (!feof(In)) {
 106       if (shutdownRequested())
 107         return error(std::make_error_code(std::errc::operation_canceled),
 108                      "Got signal, shutting down");
 109       if (ferror(In))
 110         return llvm::errorCodeToError(llvm::errnoAsErrorCode());
 111       if (readRawMessage(JSON)) {
 112         ThreadCrashReporter ScopedReporter([&JSON]() {
 113           auto &OS = llvm::errs();
 114           OS << "Signalled while processing message:\n";
 115           OS << JSON << "\n";
 116         });
 117         if (auto Doc = llvm::json::parse(JSON)) {
 118           vlog(Pretty ? "<<< {0:2}\n" : "<<< {0}\n", *Doc);
 119           if (!handleMessage(std::move(*Doc), Handler))
 120             return llvm::Error::success(); // we saw the "exit" notification.
 121         } else {
 122           // Parse error. Log the raw message.
 123           vlog("<<< {0}\n", JSON);
 124           elog("JSON parse error: {0}", llvm::toString(Doc.takeError()));
 125         }
 126       }
 127     }
 128     return llvm::errorCodeToError(std::make_error_code(std::errc::io_error));
 129   }
 130
 131 private:
 132   // Dispatches incoming message to Handler onNotify/onCall/onReply.
 133   bool handleMessage(llvm::json::Value Message, MessageHandler &Handler);
 134   // Writes outgoing message to Out stream.
 135   void sendMessage(llvm::json::Value Message) {
 136     OutputBuffer.clear();
 137     llvm::raw_svector_ostream OS(OutputBuffer);
 138     OS << llvm::formatv(Pretty ? "{0:2}" : "{0}", Message);
 139     Out << "Content-Length: " << OutputBuffer.size() << "\r\n\r\n"
 140         << OutputBuffer;
 141     Out.flush();
 142     vlog(">>> {0}\n", OutputBuffer);
 143   }
 144
 145   // Read raw string messages from input stream.
 146   bool readRawMessage(std::string &JSON) {
 147     return Style == JSONStreamStyle::Delimited ? readDelimitedMessage(JSON)
 148                                                : readStandardMessage(JSON);
 149   }
 150   bool readDelimitedMessage(std::string &JSON);
 151   bool readStandardMessage(std::string &JSON);
 152
 153   llvm::SmallVector<char, 0> OutputBuffer;
 154   std::FILE *In;
 155   llvm::raw_ostream &Out;
 156   llvm::raw_ostream &InMirror;
 157   bool Pretty;
 158   JSONStreamStyle Style;
 159 };
 160
 161 bool JSONTransport::handleMessage(llvm::json::Value Message,
 162                                   MessageHandler &Handler) {
 163   // Message must be an object with "jsonrpc":"2.0".
 164   auto *Object = Message.getAsObject();
 165   if (!Object ||
 166       Object->getString("jsonrpc") != std::optional<llvm::StringRef>("2.0")) {
 167     elog("Not a JSON-RPC 2.0 message: {0:2}", Message);
 168     return false;
 169   }
 170   // ID may be any JSON value. If absent, this is a notification.
 171   std::optional<llvm::json::Value> ID;
 172   if (auto *I = Object->get("id"))
 173     ID = std::move(*I);
 174   auto Method = Object->getString("method");
 175   if (!Method) { // This is a response.
 176     if (!ID) {
 177       elog("No method and no response ID: {0:2}", Message);
 178       return false;
 179     }
 180     if (auto *Err = Object->getObject("error"))
 181       return Handler.onReply(std::move(*ID), decodeError(*Err));
 182     // Result should be given, use null if not.
 183     llvm::json::Value Result = nullptr;
 184     if (auto *R = Object->get("result"))
 185       Result = std::move(*R);
 186     return Handler.onReply(std::move(*ID), std::move(Result));
 187   }
 188   // Params should be given, use null if not.
 189   llvm::json::Value Params = nullptr;
 190   if (auto *P = Object->get("params"))
 191     Params = std::move(*P);
 192
 193   if (ID)
 194     return Handler.onCall(*Method, std::move(Params), std::move(*ID));
 195   return Handler.onNotify(*Method, std::move(Params));
 196 }
 197
 198 // Tries to read a line up to and including \n.
 199 // If failing, feof(), ferror(), or shutdownRequested() will be set.
 200 bool readLine(std::FILE *In, llvm::SmallVectorImpl<char> &Out) {
 201   // Big enough to hold any reasonable header line. May not fit content lines
 202   // in delimited mode, but performance doesn't matter for that mode.
 203   static constexpr int BufSize = 128;
 204   size_t Size = 0;
 205   Out.clear();
 206   for (;;) {
 207     Out.resize_for_overwrite(Size + BufSize);
 208     // Handle EINTR which is sent when a debugger attaches on some platforms.
 209     if (!retryAfterSignalUnlessShutdown(
 210             nullptr, [&] { return std::fgets(&Out[Size], BufSize, In); }))
 211       return false;
 212     clearerr(In);
 213     // If the line contained null bytes, anything after it (including \n) will
 214     // be ignored. Fortunately this is not a legal header or JSON.
 215     size_t Read = std::strlen(&Out[Size]);
 216     if (Read > 0 && Out[Size + Read - 1] == '\n') {
 217       Out.resize(Size + Read);
 218       return true;
 219     }
 220     Size += Read;
 221   }
 222 }
 223
 224 // Returns None when:
 225 //  - ferror(), feof(), or shutdownRequested() are set.
 226 //  - Content-Length is missing or empty (protocol error)
 227 bool JSONTransport::readStandardMessage(std::string &JSON) {
 228   // A Language Server Protocol message starts with a set of HTTP headers,
 229   // delimited  by \r\n, and terminated by an empty line (\r\n).
 230   unsigned long long ContentLength = 0;
 231   llvm::SmallString<128> Line;
 232   while (true) {
 233     if (feof(In) || ferror(In) || !readLine(In, Line))
 234       return false;
 235     InMirror << Line;
 236
 237     llvm::StringRef LineRef = Line;
 238
 239     // We allow comments in headers. Technically this isn't part
 240
 241     // of the LSP specification, but makes writing tests easier.
 242     if (LineRef.starts_with("#"))
 243       continue;
 244
 245     // Content-Length is a mandatory header, and the only one we handle.
 246     if (LineRef.consume_front("Content-Length: ")) {
 247       if (ContentLength != 0) {
 248         elog("Warning: Duplicate Content-Length header received. "
 249              "The previous value for this message ({0}) was ignored.",
 250              ContentLength);
 251       }
 252       llvm::getAsUnsignedInteger(LineRef.trim(), 0, ContentLength);
 253       continue;
 254     }
 255
 256     // An empty line indicates the end of headers.
 257     // Go ahead and read the JSON.
 258     if (LineRef.trim().empty())
 259       break;
 260
 261     // It's another header, ignore it.
 262   }
 263
 264   // The fuzzer likes crashing us by sending "Content-Length: 9999999999999999"
 265   if (ContentLength > 1 << 30) { // 1024M
 266     elog("Refusing to read message with long Content-Length: {0}. "
 267          "Expect protocol errors",
 268          ContentLength);
 269     return false;
 270   }
 271   if (ContentLength == 0) {
 272     log("Warning: Missing Content-Length header, or zero-length message.");
 273     return false;
 274   }
 275
 276   JSON.resize(ContentLength);
 277   for (size_t Pos = 0, Read; Pos < ContentLength; Pos += Read) {
 278     // Handle EINTR which is sent when a debugger attaches on some platforms.
 279     Read = retryAfterSignalUnlessShutdown(0, [&]{
 280       return std::fread(&JSON[Pos], 1, ContentLength - Pos, In);
 281     });
 282     if (Read == 0) {
 283       elog("Input was aborted. Read only {0} bytes of expected {1}.", Pos,
 284            ContentLength);
 285       return false;
 286     }
 287     InMirror << llvm::StringRef(&JSON[Pos], Read);
 288     clearerr(In); // If we're done, the error was transient. If we're not done,
 289                   // either it was transient or we'll see it again on retry.
 290     Pos += Read;
 291   }
 292   return true;
 293 }
 294
 295 // For lit tests we support a simplified syntax:
 296 // - messages are delimited by '---' on a line by itself
 297 // - lines starting with # are ignored.
 298 // This is a testing path, so favor simplicity over performance here.
 299 // When returning false: feof(), ferror(), or shutdownRequested() will be set.
 300 bool JSONTransport::readDelimitedMessage(std::string &JSON) {
 301   JSON.clear();
 302   llvm::SmallString<128> Line;
 303   while (readLine(In, Line)) {
 304     InMirror << Line;
 305     auto LineRef = Line.str().trim();
 306     if (LineRef.starts_with("#")) // comment
 307       continue;
 308
 309     // found a delimiter
 310     if (LineRef.rtrim() == "---")
 311       break;
 312
 313     JSON += Line;
 314   }
 315
 316   if (shutdownRequested())
 317     return false;
 318   if (ferror(In)) {
 319     elog("Input error while reading message!");
 320     return false;
 321   }
 322   return true; // Including at EOF
 323 }
 324
 325 } // namespace
 326
 327 std::unique_ptr<Transport> newJSONTransport(std::FILE *In,
 328                                             llvm::raw_ostream &Out,
 329                                             llvm::raw_ostream *InMirror,
 330                                             bool Pretty,
 331                                             JSONStreamStyle Style) {
 332   return std::make_unique<JSONTransport>(In, Out, InMirror, Pretty, Style);
 333 }
 334
 335 } // namespace clangd
 336 } // namespace clang