feat: Ability to set custom fetch function as an option on HTTP transport

[bradjones1]

I am implementing a native app with React Native and use OAuth for authentication. To facilitate token refresh on demand, I am using https://github.com/badgateway/fetch-mw-oauth2 which provides a fetch middleware to retry failed requests after refreshing access tokens.

This pattern works well when clients allow setting a custom fetch function, e.g. in the case of Orbit.js (a json:api client.)

I am not really much of a TypeScript developer but I have worked this out locally and it "seems to work." Hoping this could be an easy/backwards and forwards compatible change that would make this library even better. Thanks!

[bradjones1]

I'm not really sure what to put here (not a typescript guy...) but the linter didn't like Function

[codecov]

Codecov Report

Merging #301 (dd8d207) into master (bb0ea71) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #301   +/-   ##
=======================================
  Coverage   99.26%   99.27%           
=======================================
  Files          11       11           
  Lines         410      411    +1     
  Branches       62       63    +1     
=======================================
+ Hits          407      408    +1     
  Misses          3        3           

Impacted Files	Coverage Δ
src/transports/HTTPTransport.ts	100.00% <100.00%> (ø)

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[zcstarr]

Hey sorry for the delayed response on this, but I think what you want to do here is just make a custom transport. If it's not problematic for you and reactnative you could even just extend HttpTransport and then overwrite the connect method.

 class CustomHttpTransport extends HTTPTransport {

  connect(){
   ....
  }
}

Then usage within the client context is

const transport = new CustomHTTPTransport("http://localhost:8545");
const client = new Client(new RequestManager([transport]));
const result = await client.request({method: "addition", params: [2, 2]});

If you need access to it from another part of the stack such as the generator, for now because CustomHttpTransport extends HTTPTransport, you should be able to pass the custom transport in from the generated client data.

It's possible that we've typed it too strictly from the generator side, if so could you put up an issue https://github.com/open-rpc/generator

Thanks for the PR, but I think the proper thing here is a custom transport

[bradjones1]

OK, thanks for the feedback.

[bradjones1]

This got done in basically a similar way at #330