Error Handler Middleware

errorHandler() provides a catch-all layer that logs unexpected errors, respects thrown HttpError instances, and keeps responses Fetch-friendly.

Usage

Place it near the end of your middleware chain:

import { bunway, errorHandler, HttpError } from "bunway";

const app = bunway();
app.use(errorHandler({ logger: console.error }));

app.get("/secret", () => {
  throw new HttpError(403, "Forbidden");
});

• Thrown HttpErrors become responses with their status, body, and headers.
• Non-HttpError exceptions yield a 500 JSON payload ({"error":"Internal Server Error"}) and optional logging.
• If you throw/return a native Response, the middleware simply passes it through.

Mapping custom errors

Use the map option to translate domain exceptions into HttpError instances:

app.use(
  errorHandler({
    logger: console.error,
    map: (err) => {
      if (err instanceof SyntaxError) return new HttpError(400, "Invalid JSON payload");
      if (err instanceof AuthError) return new HttpError(401, err.message);
      return null; // fallback to default handling
    },
  })
);

The mapping function may return:

• HttpError – used directly
• Error – re-thrown so the standard branch handles it
• null/undefined – skip mapping

Custom responses

Need to return a custom Response? Throw or return the Response directly inside the handler—errorHandler() passes it through untouched.

Logging

Provide logger to capture unexpected errors. bunway wraps calls in try/catch so logging failures don’t crash the app. Example logger signature: (error, ctx) => void.

Response format

When a handler throws HttpError(404, "Not found"):

HTTP/1.1 404 Not Found
Content-Type: application/json

{"error":"Not found"}

If the request’s Accept header prefers text (text/plain), bunway returns a plain-text body instead.

Tips

• Combine with cors() so even error responses contain the correct CORS headers.
• Use ctx.req.locals to pass debugging info to the logger.
• Keep error messages client-safe; internal stack traces shouldn’t leak to users. Log detailed errors server-side instead.

For option details see ErrorHandlerOptions in the API Reference.