feat: fleshing out error handling

Related #500

[ci skip]

src/RPC/RPCServer.ts

@@ -11,6 +11,7 @@ import type { ReadableWritablePair } from 'stream/web';
 import type { JSONValue, POJO } from '../types';
 import type { ConnectionInfo } from '../network/types';
 import type { UnaryHandler } from './types';
+import type { RPCErrorEvent } from './utils';
 import { ReadableStream } from 'stream/web';
 import { CreateDestroy, ready } from '@matrixai/async-init/dist/CreateDestroy';
 import Logger from '@matrixai/logger';
@@ -42,8 +43,8 @@ class RPCServer {
   protected logger: Logger;
   protected handlerMap: Map<string, DuplexStreamHandler<JSONValue, JSONValue>> =
     new Map();
-  private activeStreams: Set<PromiseCancellable<void>> = new Set();
-  private events: EventTarget = new EventTarget();
+  protected activeStreams: Set<PromiseCancellable<void>> = new Set();
+  protected events: EventTarget = new EventTarget();
 
   public constructor({
     container,
@@ -164,6 +165,7 @@ class RPCServer {
     const container = this.container;
     const handlerMap = this.handlerMap;
     const ctx = { signal: abortController.signal };
+    const events = this.events;
     const outputGen = async function* (): AsyncGenerator<JsonRpcMessage> {
       // Step 1, authentication and establishment
       // read the first message, lets assume the first message is always leading
@@ -207,20 +209,29 @@ class RPCServer {
           yield responseMessage;
         }
       } catch (e) {
-        // This would be an error from the handler or the streams. We should
-        // catch this and send an error message back through the stream.
-        const rpcError: JsonRpcError = {
-          code: e.exitCode,
-          message: e.description,
-          data: rpcUtils.fromError(e),
-        };
-        const rpcErrorMessage: JsonRpcResponseError = {
-          jsonrpc: '2.0',
-          error: rpcError,
-          id: null,
-        };
-        // TODO: catch this and emit error in the event emitter
-        yield rpcErrorMessage;
+        if (rpcUtils.isReturnableError(e)) {
+          // We want to convert this error to an error message and pass it along
+          const rpcError: JsonRpcError = {
+            code: e.exitCode,
+            message: e.description,
+            data: rpcUtils.fromError(e),
+          };
+          const rpcErrorMessage: JsonRpcResponseError = {
+            jsonrpc: '2.0',
+            error: rpcError,
+            id: null,
+          };
+          yield rpcErrorMessage;
+        } else {
+          // These errors are emitted to the event system
+          events.dispatchEvent(
+            new rpcUtils.RPCErrorEvent({
+              detail: {
+                error: e,
+              },
+            }),
+          );
+        }
       }
       resolve();
     };
@@ -245,6 +256,22 @@ class RPCServer {
       .pipeTo(streamPair.writable)
       .catch(() => {});
   }
+
+  public addEventListener(
+    type: 'error',
+    callback: (event: RPCErrorEvent) => void,
+    options?: boolean | AddEventListenerOptions | undefined,
+  ) {
+    this.events.addEventListener(type, callback, options);
+  }
+
+  public removeEventListener(
+    type: 'error',
+    callback: (event: RPCErrorEvent) => void,
+    options?: boolean | AddEventListenerOptions | undefined,
+  ) {
+    this.events.removeEventListener(type, callback, options);
+  }
 }
 
 export default RPCServer;

src/RPC/errors.ts

@@ -47,6 +47,11 @@ class ErrorRpcRemoteError<T> extends ErrorRpc<T> {
   exitCode = sysexits.UNAVAILABLE;
 }
 
+class ErrorRpcPlaceholderConnectionError<T> extends ErrorRpc<T> {
+  static description = 'placeholder error for connection stream failure';
+  exitCode = sysexits.UNAVAILABLE;
+}
+
 export {
   ErrorRpc,
   ErrorRpcRunning,
@@ -58,4 +63,5 @@ export {
   ErrorRpcProtocal,
   ErrorRpcMessageLength,
   ErrorRpcRemoteError,
+  ErrorRpcPlaceholderConnectionError,
 };

src/RPC/utils.ts

@@ -475,6 +475,28 @@ class ClientOutputTransformerStream<
   }
 }
 
+function isReturnableError(e: Error): boolean {
+  if (e instanceof rpcErrors.ErrorRpcPlaceholderConnectionError) return false;
+  return true;
+}
+
+class RPCErrorEvent extends Event {
+  public detail: {
+    error: any;
+  };
+
+  constructor(
+    options: EventInit & {
+      detail: {
+        error: any;
+      };
+    },
+  ) {
+    super('error', options);
+    this.detail = options.detail;
+  }
+}
+
 export {
   JsonToJsonMessageStream,
   JsonMessageToJsonStream,
@@ -489,4 +511,6 @@ export {
   toError,
   ClientInputTransformerStream,
   ClientOutputTransformerStream,
+  isReturnableError,
+  RPCErrorEvent,
 };

tests/RPC/RPCServer.test.ts

@@ -12,6 +12,7 @@ import type { ReadableWritablePair } from 'stream/web';
 import { testProp, fc } from '@fast-check/jest';
 import Logger, { LogLevel, StreamHandler } from '@matrixai/logger';
 import RPCServer from '@/RPC/RPCServer';
+import * as rpcErrors from '@/RPC/errors';
 import * as rpcTestUtils from './utils';
 
 describe(`${RPCServer.name}`, () => {
@@ -289,6 +290,85 @@ describe(`${RPCServer.name}`, () => {
     await rpcServer.destroy();
   });
 
+  const errorArb = fc.oneof(
+    fc.constant(new rpcErrors.ErrorRpcParse()),
+    fc.constant(new rpcErrors.ErrorRpcHandlerMissing()),
+    fc.constant(new rpcErrors.ErrorRpcProtocal()),
+    fc.constant(new rpcErrors.ErrorRpcMessageLength()),
+    fc.constant(new rpcErrors.ErrorRpcRemoteError()),
+  );
+  testProp(
+    'should send error message',
+    [specificMessageArb, errorArb],
+    async (messages, error) => {
+      const stream = rpcTestUtils.jsonRpcStream(messages);
+      const container = {};
+      const rpcServer = await RPCServer.createRPCServer({ container, logger });
+      let resolve, reject;
+      const errorProm = new Promise((resolve_, reject_) => {
+        resolve = resolve_;
+        reject = reject_;
+      });
+      rpcServer.addEventListener('error', (thing) => {
+        resolve(thing);
+      });
+      const [outputResult, outputStream] = rpcTestUtils.streamToArray();
+      const readWriteStream: ReadableWritablePair = {
+        readable: stream,
+        writable: outputStream,
+      };
+
+      const duplexHandler: DuplexStreamHandler<JSONValue, JSONValue> =
+        async function* (_input, _container, _connectionInfo, _ctx) {
+          throw error;
+        };
+
+      rpcServer.registerDuplexStreamHandler(methodName, duplexHandler);
+      rpcServer.handleStream(readWriteStream, {} as ConnectionInfo);
+      const errorMessage = JSON.parse((await outputResult)[0]!.toString());
+      expect(errorMessage.error.code).toEqual(error.exitCode);
+      expect(errorMessage.error.message).toEqual(error.description);
+      reject();
+      await expect(errorProm).toReject();
+      await rpcServer.destroy();
+    },
+  );
+  testProp(
+    'should emit stream error',
+    [specificMessageArb],
+    async (messages) => {
+      const stream = rpcTestUtils.jsonRpcStream(messages);
+      const container = {};
+      const rpcServer = await RPCServer.createRPCServer({ container, logger });
+      let resolve, reject;
+      const errorProm = new Promise((resolve_, reject_) => {
+        resolve = resolve_;
+        reject = reject_;
+      });
+      rpcServer.addEventListener('error', (thing) => {
+        resolve(thing);
+      });
+      const [outputResult, outputStream] = rpcTestUtils.streamToArray();
+      const readWriteStream: ReadableWritablePair = {
+        readable: stream,
+        writable: outputStream,
+      };
+
+      const duplexHandler: DuplexStreamHandler<JSONValue, JSONValue> =
+        async function* (_input, _container, _connectionInfo, _ctx) {
+          throw new rpcErrors.ErrorRpcPlaceholderConnectionError();
+        };
+
+      rpcServer.registerDuplexStreamHandler(methodName, duplexHandler);
+      rpcServer.handleStream(readWriteStream, {} as ConnectionInfo);
+      await outputResult;
+
+      await rpcServer.destroy();
+      reject();
+      await expect(errorProm).toResolve();
+    },
+  );
+
   // TODO:
   //  - Test odd conditions for handlers, like extra messages where 1 is expected.
   //  - Expectations can't be inside the handlers otherwise they're caught.