feat: preserve and make error cause accessable

src/app.ts

@@ -6,7 +6,7 @@ import {
   eventHandler,
   H3Event,
 } from "./event";
-import { createError } from "./error";
+import { H3Error, createError } from "./error";
 import {
   send,
   sendStream,
@@ -48,7 +48,7 @@ export interface AppUse {
 
 export interface AppOptions {
   debug?: boolean;
-  onError?: (error: Error, event: H3Event) => any;
+  onError?: (error: H3Error, event: H3Event) => any;
 }
 
 export interface App {

src/error.ts

@@ -25,6 +25,17 @@ export class H3Error extends Error {
   unhandled = false;
   statusMessage?: string;
   data?: any;
+  cause?: unknown;
+
+  constructor(message: string, opts: { cause?: unknown } = {}) {
+    // @ts-ignore https://v8.dev/features/error-cause
+    super(message, opts);
+
+    // Polyfill cause for other runtimes
+    if (opts.cause && !this.cause) {
+      this.cause = opts.cause;
+    }
+  }
 
   toJSON() {
     const obj: Pick<
@@ -63,11 +74,9 @@ export function createError(
     return input;
   }
 
-  const err = new H3Error(
-    input.message ?? input.statusMessage ?? "",
-    // @ts-ignore https://v8.dev/features/error-cause
-    input.cause ? { cause: input.cause } : undefined
-  );
+  const err = new H3Error(input.message ?? input.statusMessage ?? "", {
+    cause: input.cause || input,
+  });
 
   if ("stack" in input) {
     try {

test/error.test.ts

@@ -1,11 +1,12 @@
 import supertest, { SuperTest, Test } from "supertest";
-import { describe, it, expect, beforeEach, vi } from "vitest";
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
 import {
   createApp,
   App,
   createError,
   toNodeListener,
   eventHandler,
+  H3Error,
 } from "../src";
 
 const consoleMock = ((global.console.error as any) = vi.fn());
@@ -14,11 +15,22 @@ describe("error", () => {
   let app: App;
   let request: SuperTest<Test>;
 
+  const capturedErrors: H3Error[] = [];
+
   beforeEach(() => {
-    app = createApp({ debug: false });
+    app = createApp({
+      debug: false,
+      onError(error) {
+        capturedErrors.push(error);
+      },
+    });
     request = supertest(toNodeListener(app));
   });
 
+  afterEach(() => {
+    capturedErrors.length = 0;
+  });
+
   it("logs errors", async () => {
     app.use(
       eventHandler(() => {
@@ -119,4 +131,22 @@ describe("error", () => {
     const res = await request.get("/");
     expect(res.status).toBe(501);
   });
+
+  it("can access original error", async () => {
+    class CustomError extends Error {
+      customError: true;
+    }
+
+    app.use(
+      "/",
+      eventHandler(() => {
+        throw createError(new CustomError());
+      })
+    );
+
+    const res = await request.get("/");
+    expect(res.status).toBe(500);
+
+    expect(capturedErrors[0].cause).toBeInstanceOf(CustomError);
+  });
 });