[mlir-lsp] Log invalid notification params (#89856)

When the `lsp::MessageHandler` processes a request with invalid params
(that is, the "params" JSON sent along with the request does not match
the shape expected by the message handler for the given method), it
replies by sending an error response to the client.

On the other hand, the language server protocol specifies that
notifications must not result in responses. As a result, when the
JSON params accompanying a notification cannot be parsed, no error is
sent back; there is no indication that an error has occurred at all.

This patch adds an error log for that case. Although clients cannot
parse error logs, this at least provides an indication that something
went wrong on the language server side.

Author: modocache

mlir/include/mlir/Tools/lsp-server-support/Transport.h

@@ -147,9 +147,15 @@ class MessageHandler {
                     void (ThisT::*handler)(const Param &)) {
     notificationHandlers[method] = [method, handler,
                                     thisPtr](llvm::json::Value rawParams) {
-      llvm::Expected<Param> param = parse<Param>(rawParams, method, "request");
-      if (!param)
-        return llvm::consumeError(param.takeError());
+      llvm::Expected<Param> param =
+          parse<Param>(rawParams, method, "notification");
+      if (!param) {
+        return llvm::consumeError(
+            llvm::handleErrors(param.takeError(), [](const LSPError &lspError) {
+              Logger::error("JSON parsing error: {0}",
+                            lspError.message.c_str());
+            }));
+      }
       (thisPtr->*handler)(*param);
     };
   }

mlir/unittests/Tools/lsp-server-support/Transport.cpp

@@ -7,7 +7,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "mlir/Tools/lsp-server-support/Transport.h"
-#include "llvm/ADT/ScopeExit.h"
+#include "mlir/Tools/lsp-server-support/Logging.h"
+#include "mlir/Tools/lsp-server-support/Protocol.h"
 #include "llvm/Support/FileSystem.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
@@ -29,37 +30,92 @@ TEST(TransportTest, SendReply) {
   EXPECT_THAT(out, HasSubstr("\"result\":null"));
 }
 
-TEST(TransportTest, MethodNotFound) {
-  auto tempOr = llvm::sys::fs::TempFile::create("lsp-unittest-%%%%%%.json");
-  ASSERT_TRUE((bool)tempOr);
-  auto discardTemp =
-      llvm::make_scope_exit([&]() { ASSERT_FALSE((bool)tempOr->discard()); });
+class TransportInputTest : public Test {
+  std::optional<llvm::sys::fs::TempFile> inputTempFile;
+  std::FILE *in = nullptr;
+  std::string output = "";
+  llvm::raw_string_ostream os;
+  std::optional<JSONTransport> transport = std::nullopt;
+  std::optional<MessageHandler> messageHandler = std::nullopt;
 
-  {
+protected:
+  TransportInputTest() : os(output) {}
+
+  void SetUp() override {
+    auto tempOr = llvm::sys::fs::TempFile::create("lsp-unittest-%%%%%%.json");
+    ASSERT_TRUE((bool)tempOr);
+    llvm::sys::fs::TempFile t = std::move(*tempOr);
+    inputTempFile = std::move(t);
+
+    in = std::fopen(inputTempFile->TmpName.c_str(), "r");
+    transport.emplace(in, os, JSONStreamStyle::Delimited);
+    messageHandler.emplace(*transport);
+  }
+
+  void TearDown() override {
+    EXPECT_FALSE(inputTempFile->discard());
+    EXPECT_EQ(std::fclose(in), 0);
+  }
+
+  void writeInput(StringRef buffer) {
     std::error_code ec;
-    llvm::raw_fd_ostream os(tempOr->TmpName, ec);
+    llvm::raw_fd_ostream os(inputTempFile->TmpName, ec);
     ASSERT_FALSE(ec);
-    os << "{\"jsonrpc\":\"2.0\",\"id\":29,\"method\":\"ack\"}\n";
+    os << buffer;
     os.close();
   }
 
-  std::string out;
-  llvm::raw_string_ostream os(out);
-  std::FILE *in = std::fopen(tempOr->TmpName.c_str(), "r");
-  auto closeIn = llvm::make_scope_exit([&]() { std::fclose(in); });
+  StringRef getOutput() const { return output; }
+  MessageHandler &getMessageHandler() { return *messageHandler; }
 
-  JSONTransport transport(in, os, JSONStreamStyle::Delimited);
-  MessageHandler handler(transport);
+  void runTransport() {
+    bool gotEOF = false;
+    llvm::Error err = llvm::handleErrors(
+        transport->run(*messageHandler), [&](const llvm::ECError &ecErr) {
+          gotEOF = ecErr.convertToErrorCode() == std::errc::io_error;
+        });
+    llvm::consumeError(std::move(err));
+    EXPECT_TRUE(gotEOF);
+  }
+};
+
+TEST_F(TransportInputTest, RequestWithInvalidParams) {
+  struct Handler {
+    void onMethod(const TextDocumentItem &params,
+                  mlir::lsp::Callback<TextDocumentIdentifier> callback) {}
+  } handler;
+  getMessageHandler().method("invalid-params-request", &handler,
+                             &Handler::onMethod);
+
+  writeInput("{\"jsonrpc\":\"2.0\",\"id\":92,"
+             "\"method\":\"invalid-params-request\",\"params\":{}}\n");
+  runTransport();
+  EXPECT_THAT(getOutput(), HasSubstr("error"));
+  EXPECT_THAT(getOutput(), HasSubstr("missing value at (root).uri"));
+}
+
+TEST_F(TransportInputTest, NotificationWithInvalidParams) {
+  // JSON parsing errors are only reported via error logging. As a result, this
+  // test can't make any expectations -- but it prints the output anyway, by way
+  // of demonstration.
+  Logger::setLogLevel(Logger::Level::Error);
+
+  struct Handler {
+    void onNotification(const TextDocumentItem &params) {}
+  } handler;
+  getMessageHandler().notification("invalid-params-notification", &handler,
+                                   &Handler::onNotification);
+
+  writeInput("{\"jsonrpc\":\"2.0\",\"method\":\"invalid-params-notification\","
+             "\"params\":{}}\n");
+  runTransport();
+}
 
-  bool gotEOF = false;
-  llvm::Error err = llvm::handleErrors(
-      transport.run(handler), [&](const llvm::ECError &ecErr) {
-        gotEOF = ecErr.convertToErrorCode() == std::errc::io_error;
-      });
-  llvm::consumeError(std::move(err));
-  EXPECT_TRUE(gotEOF);
-  EXPECT_THAT(out, HasSubstr("\"id\":29"));
-  EXPECT_THAT(out, HasSubstr("\"error\""));
-  EXPECT_THAT(out, HasSubstr("\"message\":\"method not found: ack\""));
+TEST_F(TransportInputTest, MethodNotFound) {
+  writeInput("{\"jsonrpc\":\"2.0\",\"id\":29,\"method\":\"ack\"}\n");
+  runTransport();
+  EXPECT_THAT(getOutput(), HasSubstr("\"id\":29"));
+  EXPECT_THAT(getOutput(), HasSubstr("\"error\""));
+  EXPECT_THAT(getOutput(), HasSubstr("\"message\":\"method not found: ack\""));
 }
 } // namespace