CORS issue on netlify POST function

Support
,
1

I have a netlify function that needs to be exposed to applications running on different domains.

https://cryptomint.one/.netlify/functions/sendGift

The method returns the following response headers to allow cross domain access

  'Content-Type': 'application/json',
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Headers': 'Content-Type',
  'Access-Control-Allow-Methods': 'GET, HEAD, PUT, POST, OPTIONS, DELETE',

When invoked as a GET the endpoint returns an HTTP 405 response which is precisely what I would expect as the code dictates.

    if (httpMethod !== 'POST') {
      return { statusCode: 405, body: "Method Not Allowed" };
    }

This endpoint is a POST. When invoked as a POST with a pay load I see the dreaded CORS error.

However when invoked as a POST with no payload the method succeeds. Well it responds with an HTTP 400 as it expects a payload, but no CORS error and that response is again function code dictated.

I have not the faintest idea what the issue could be here nor what form a resolution could take. I have tried implementing a PUT however the results are the same.

The payload is too large to use path parameters.

2

Seems the preflight requires an HTTP 204 response, so the following fixed it

    if (httpMethod === 'OPTIONS') {
      return getNoContentResponse();
    } else if (httpMethod !== 'POST') {
      return getMethodNotAllowedResponse();
    }
1 Like