Access context in rewriteHeaders

[alex-parra]

Fix #431

On gateway setups, query context was not being exposed to rewriteHeaders.
This PR fixes the issue by passing the context to every call to serviceDefinition.sendRequest which then exposes it to rewriteHeaders as an additional parameter.

[simoneb]

if there's no context, do we need to provide a fake one then or would leaving it undefined be a more sensible default than providing an empty object then?

[simoneb]

maybe I'm missing it, but I don't see where this file tests that rewriteHeaders is actually called and, more importantly, that its return value is actually used.

[alex-parra]

Tests to rewriteHeaders are at line 64 and 65

[mcollina]

lgtm

[simoneb]

LGTM, see inline comment.

[Santinell]

@alex-parra @mcollina
I thought that in rewriteHeaders I will have the same context as generated in context method of gateway.
Like this:

 const rewriteHeaders = (headers, context) => {
    // I expect that here I will have the same context as in method `context` followed below
    return { context: JSON.stringify(context) };
  };
  app.register(mercurius, {
    context: async req => {
      const ctx = await authByHeaders(req.headers);
      return ctx;
    },
    gateway: {
      pollingInterval: 3000,
      services: [
        { name: 'host', url: 'http://localhost:3001/', rewriteHeaders },
        { name: 'dict', url: 'http://localhost:3002/', rewriteHeaders }
      ]
    }
  });

My use-case is auth on gateway side and sending context to services via rewriteHeaders

For now I have to implement auth on all services, even which don't use database for its methods. It's a huge overhead in packages and runtime, when one query using 3-5 services and every of them should auth.

Is it possible to get data from context method to rewriteHeaders?
Converting method rewriteHeaders to asynchronous is also can make it working.

[mcollina]

I think it should be the same context. Please open a new issue with a full reproducible example. Thanks.

[Santinell]

I am sorry, problem was because sometimes context is undefined. I haven't expected such value and it led to error on request its fields.
When I made it empty object by default this problem was resolved