typing for proxyRes seems to be incorrect

[dylang]

Steps to reproduce

Using TypeScript, this is valid but throws an error.

// options
onProxyRes: (proxyRes, req, res) => {
  const incomingCookies = proxyRes.getHeader(SET_COOKIE_HEADER);
  // etc
},

Expected behavior

• TypeScript doesn't expect proxyRes.getHeader, proxyRes.hasHeader, proxyRes.setHeader to be methods available.
• TypeScript expects proxyRes.headers to be an array of strings.

Actual behavior

 ✖  uncaughtException (an exception was thrown but not caught)  TypeError: proxyRes.getHeader is not a function
    at ProxyServer.onProxyRes (proxy.ts)

Workaround

proxyRes.headers works as expected, so adding this code works, but it would be cleaner to just have the correct types.

// options
onProxyRes: (
  proxyRes: ServerResponse & { headers: { [name: string]: string[] } },
  req,
  res
) => {
  const incomingCookies = proxyRes.headers[SET_COOKIE_HEADER];
  // etc
},

I'm not sure what type the proxyRes should be.

client info

I'm using latest Express.

Reproducible Demo

I can create one if necessary.

[chimurai]

Nice catch. I used the community types as starting point to include the types in HPM.

Looks like they have the same issue:

https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/http-proxy/index.d.ts#L136

https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/http-proxy-middleware/index.d.ts#L38

I'm also not sure what type proxyRes should be; Since that proxyRes is coming from the http-proxy library.

Definitely wouldn't mind your help to make the typing more correct.
Feel free to give it a shot.

[dylang]

Right now in this module it's http.ServerResponse.

It seems like it should be http.IncomingMessage.

I'm curious if you know why it was http.ServerResponse instead - I haven't had a chance to try this yet and could be wrong.

[chimurai]

Think it might be a booboo from my side.

[dylang]

Changing proxyRes to http.IncomingMessage fixed those types for me! Would you like a PR?

[chimurai]

That would be awesome!