在 fp-ts 中使用 TaskEither 和 fetch API

Question

I want to wrap Fetch API in fp-ts in some manner:

1. create request
2. check status
3. if status is ok - return json

import * as TE from 'fp-ts/lib/TaskEither';
import * as E from 'fp-ts/lib/Either';
import { flow } from 'fp-ts/lib/function';
import { pipe } from 'fp-ts/lib/pipeable';

const safeGet = (url: string): TE.TaskEither<Error, Response> => TE.tryCatch(
  () => fetch(url),
  (reason) => new Error(String(reason))
);

const processResponce = flow(
  (x: Response): E.Either<Error, Response> => {
    return x.status === 200
      ? E.right(x)
      : E.left(Error(x.statusText))
  },
  TE.fromEither
);

export const httpGet = (url: string): TE.TaskEither<Error, Response> => pipe(
  safeGet(url),
  TE.chain(processResponce)
);

With this example after running httpGet I get an Response and need to eval.json() method manually. So how can I avoid this behavior and get json inside pipe?

Answer 1

Just chain this into your flow?

const safeJson = <T = unknown>(resp: Response): TE.TaskEither<Error, T> => TE.tryCatch(
  () => resp.json(),
  (reason) => new Error(String(reason))
);