Override instanceof for ConnectError (#974)

packages/connect-web-bench/README.md

@@ -10,5 +10,5 @@ it like a web server would usually do.
 
 | code generator | bundle size        | minified               | compressed           |
 |----------------|-------------------:|-----------------------:|---------------------:|
-| connect        | 117,288 b | 50,936 b | 13,659 b |
+| connect        | 117,695 b | 51,217 b | 13,743 b |
 | grpc-web       | 415,212 b    | 300,936 b    | 53,420 b |

packages/connect/src/connect-error.spec.ts

@@ -26,6 +26,32 @@ import { node16FetchHeadersPolyfill } from "./node16-polyfill-helper.spec.js";
 
 node16FetchHeadersPolyfill();
 
+class ConnectError2 extends Error {
+  readonly code: Code;
+  readonly metadata: Headers;
+  details: Message[];
+  readonly rawMessage: string;
+  override name = "ConnectError";
+  cause: unknown;
+
+  constructor(
+    message: string,
+    code: Code = Code.Unknown,
+    metadata?: HeadersInit,
+    outgoingDetails?: Message[],
+    cause?: unknown,
+  ) {
+    super(message);
+    // see https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-2.html#example
+    Object.setPrototypeOf(this, new.target.prototype);
+    this.rawMessage = message;
+    this.code = code;
+    this.metadata = new Headers(metadata ?? {});
+    this.details = outgoingDetails ?? [];
+    this.cause = cause;
+  }
+}
+
 describe("ConnectError", () => {
   describe("constructor", () => {
     it("should have status unknown by default", () => {
@@ -137,6 +163,20 @@ describe("ConnectError", () => {
       expect(got.cause).toBe(error);
     });
   });
+  describe("instanceof", () => {
+    it("works for the actual ConnectError", () => {
+      expect(new ConnectError("foo")).toBeInstanceOf(ConnectError);
+    });
+    it("works for ConnectError like errors", () => {
+      expect(new ConnectError2("foo")).toBeInstanceOf(ConnectError);
+    });
+    it("fails for other errors", () => {
+      expect(new Error("foo")).not.toBeInstanceOf(ConnectError);
+      expect(null).not.toBeInstanceOf(ConnectError);
+      expect(undefined).not.toBeInstanceOf(ConnectError);
+      expect("err").not.toBeInstanceOf(ConnectError);
+    });
+  });
 });
 
 describe("assertConnectError() example", () => {

packages/connect/src/connect-error.ts

@@ -130,6 +130,26 @@ export class ConnectError extends Error {
     return new ConnectError(String(reason), code, undefined, undefined, reason);
   }
 
+  static [Symbol.hasInstance](v: unknown): boolean {
+    if (!(v instanceof Error)) {
+      return false;
+    }
+    if (Object.getPrototypeOf(v) === ConnectError.prototype) {
+      return true;
+    }
+    return (
+      v.name === "ConnectError" &&
+      "code" in v &&
+      typeof v.code === "number" &&
+      "metadata" in v &&
+      "details" in v &&
+      Array.isArray(v.details) &&
+      "rawMessage" in v &&
+      typeof v.rawMessage == "string" &&
+      "cause" in v
+    );
+  }
+
   /**
    * Retrieve error details from a ConnectError. On the wire, error details are
    * wrapped with google.protobuf.Any, so that a server or middleware can attach