aws-lambda should catch exceptions with 'httpCode' information, and correctly emit http errors (if no error middleware is used).

[universalhandle]

Hello.

I saw curveball/core#92, but I must be missing something. I've got code like this:

// handler.ts
import { Application, invokeMiddlewares } from '@curveball/core';
import handler from '@curveball/aws-lambda';
import { fooRoutes } from './components/foo/routes';

const app = new Application();
app.use(ctx => invokeMiddlewares(ctx, fooRoutes));

export const router = handler(app);

// components/foo/routes.ts
import router from '@curveball/router';
import { fooController } from './controller'; // just has a "get" method

export const fooRoutes = [
  router('/:id/foo', fooController),
];

The relevant bit of serverless.yml looks like so:

functions:
  my-function:
    handler: src/handler.router
    events:
      - http:
          # sends everything through to the router
          path: /{proxy+}
          method: any

When I visit localhost:3000/12345/foo, I get the expected result.

When I visit any other path (note: I've defined none), I get a 200 and an empty page. I would expect a 404 or a 405. Is handling of nonexistent routes not automagic? Did I miss a step?

If it's not handled automatically, is there a recommend best practice? (I didn't try too long, but a wildcard route didn't seem to do the trick either.)

Thanks!

[evert]

When @curveball/core executes all middlewares, and reaches all the way to the end it runs a 'NotFound' middleware.
tt
This middleware throws an exception. The 'normal curveball http server' path catches any exception, and emits a plain text error + http status code.

The @curveball/aws-lambda path does not catch this exception and do anything with this. Normally this would simply cause the lambda execution to fail, but I suspect that the serverless framework catches it, and return the 200 maybe? It is weird that it would do that!

A quick solution to this is to add the @curveball/problem middleware. This middleware catches errors and turns them into nicer looking application/problem+json errors.

I do think that @curveball/aws-lambda should behave as the regular server though, and emit errors that have a httpStatus property, but it also makes sense to me that other uncaught exceptions should bubble up to AWS Lambda itself as a critical failure, so it will show up as such in monitoring utilities.

tl;dr:

1. There is a bug here.
2. A quick workaround is to use @curveball/problem.
3. The fix for this should not catch non-http errors, so if the parent framework eats up exceptions and turns them into 200 OK, that's still pretty weird to me!

[universalhandle]

Hey, thanks for your super speedy response!

You got me thinking and I tried a few more things. Not sure if any of this is helpful, but I doubt it can hurt!

Note that the example I gave above has serverless passing everything through via the path: /{proxy+} configuration. For everything that follows, I have set http events explicitly per below:

functions:
  my-function:
    handler: src/handler.router
    events:
      - http:
          path: /{id}/foo
          method: any
      - http:
          path: /bar
          method: any

For a path /unknown/to/both/serverless/and/curveball I get a 404 and a message Serverless-offline: route not found.

Suppose I forget to add a route to my curveball config for path /bar. In this case, Chrome gives me a 200 and a blank page. Firefox gives me a 200 and asks me to download a zero-length file:

The problem middleware doesn't seem to do the trick for me. I've updated my code as follows, and I see no change in behavior:

// handler.ts
import { Application, invokeMiddlewares } from '@curveball/core';
import handler from '@curveball/aws-lambda';
import problemMiddleware from '@curveball/problem';
import { fooRoutes } from './components/foo/routes';

const app = new Application();
const middlewares = [ problemMiddleware(), ... fooRoutes ];
app.use(ctx => invokeMiddlewares(ctx, middlewares));

export const router = handler(app);

If you're not able to reproduce, I could set up a code sandbox somewhere. If you have a preferred tool for that, let me know.

Thanks again for your help.