@n1ru4l/push-pull-async-iterable-iterator

Create an AsyncIterableIterator from anything (on any modern platform) while handling back-pressure!

yarn install -E @n1ru4l/push-pull-async-iterable-iterator

Standalone Usage

import { makePushPullAsyncIterableIterator } from "@n1ru4l/push-pull-async-iterable-iterator";

const {
  pushValue,
  asyncIterableIterator
} = makePushPullAsyncIterableIterator();
pushValue(1);
pushValue(2);
pushValue(3);

// prints 1, 2, 3
for await (const value of asyncIterableIterator) {
  console.log(value);
}

Check if something is an AsyncIterable

import { isAsyncIterable } from "@n1ru4l/push-pull-async-iterable-iterator";

if (isAsyncIterable(something)) {
  for await (const value of something) {
    console.log(value);
  }
}

Note: On Safari iOS Symbol.asyncIterator is not available, therefore all async iterators used must be build using AsyncGenerators. If a AsyncIterable that is NO AsyncGenerator is passed to isAsyncIterable on the Safari iOS environment, it will throw an error.

Wrap a Sink

import { makeAsyncIterableIteratorFromSink } from "@n1ru4l/push-pull-async-iterable-iterator";
// let's use some GraphQL client :)
import { createClient } from "graphql-ws/lib/use/ws";

const client = createClient({
  url: "ws://localhost:3000/graphql"
});

const asyncIterableIterator = makeAsyncIterableIteratorFromSink(sink => {
  const dispose = client.subscribe(
    {
      query: "{ hello }"
    },
    {
      next: sink.next,
      error: sink.error,
      complete: sink.complete
    }
  );
  return () => dispose();
});

for await (const value of asyncIterableIterator) {
  console.log(value);
}

Apply an AsyncIterableIterator to a sink

import Observable from "zen-observable";
import {
  makePushPullAsyncIterableIterator,
  applyAsyncIterableIteratorToSink
} from "@n1ru4l/push-pull-async-iterable-iterator";

const { asyncIterableIterator } = makePushPullAsyncIterableIterator();

const observable = new Observable(sink => {
  const dispose = applyAsyncIterableIteratorToSink(asyncIterableIterator, sink);
  // dispose will be called when the observable subscription got destroyed
  // the dispose call will ensure that the async iterator is completed.
  return () => dispose();
});

const subscription = observable.subscribe({
  next: console.log,
  complete: () => console.log("done."),
  error: () => console.log("error.")
});

const interval = setInterval(() => {
  iterator.push("hi");
}, 1000);

setTimeout(() => {
  subscription.unsubscribe();
  clearInterval(interval);
}, 5000);

Put it all together

import { Observable, RequestParameters, Variables } from "relay-runtime";
import { createClient } from "graphql-ws/lib/use/ws";
import {
  makeAsyncIterableFromSink,
  applyAsyncIterableIteratorToSink
} from "@n1ru4l/push-pull-async-iterable-iterator";
import { createApplyLiveQueryPatch } from "@n1ru4l/graphql-live-query-patch";

const client = createClient({
  url: "ws://localhost:3000/graphql"
});

export const execute = (request: RequestParameters, variables: Variables) => {
  if (!request.text) {
    throw new Error("Missing document.");
  }
  const query = request.text;

  return Observable.create<GraphQLResponse>(sink => {
    // Create our asyncIterator from a Sink
    const executionResultIterator = makeAsyncIterableFromSink(wsSink => {
      const dispose = client.subscribe({ query }, wsSink);
      return () => dispose();
    });

    const applyLiveQueryPatch = createApplyLiveQueryPatch();

    // apply some middleware to our asyncIterator
    const compositeIterator = applyLiveQueryPatch(executionResultIterator);

    // Apply our async iterable to the relay sink
    // unfortunately relay cannot consume an async iterable right now.
    const dispose = applyAsyncIterableIteratorToSink(compositeIterator, sink);
    // dispose will be called by relay when the observable is disposed
    // the dispose call will ensure that the async iterator is completed.
    return () => dispose();
  });
};

TSDX User Guide

Congrats! You just saved yourself hours of work by bootstrapping this project with TSDX. Let’s get you oriented with what’s here and how to use it.

This TSDX setup is meant for developing libraries (not apps!) that can be published to NPM. If you’re looking to build a Node app, you could use ts-node-dev, plain ts-node, or simple tsc.

If you’re new to TypeScript, checkout this handy cheatsheet

Commands

TSDX scaffolds your new library inside /src.

To run TSDX, use:

npm start # or yarn start

This builds to /dist and runs the project in watch mode so any edits you save inside src causes a rebuild to /dist.

To do a one-off build, use npm run build or yarn build.

To run tests, use npm test or yarn test.

Configuration

Code quality is set up for you with prettier, husky, and lint-staged. Adjust the respective fields in package.json accordingly.

Jest

Jest tests are set up to run with npm test or yarn test.

Bundle Analysis

size-limit is set up to calculate the real cost of your library with npm run size and visualize the bundle with npm run analyze.

Setup Files

This is the folder structure we set up for you:

/src
  index.tsx       # EDIT THIS
/test
  blah.test.tsx   # EDIT THIS
.gitignore
package.json
README.md         # EDIT THIS
tsconfig.json

Rollup

TSDX uses Rollup as a bundler and generates multiple rollup configs for various module formats and build settings. See Optimizations for details.

TypeScript

tsconfig.json is set up to interpret dom and esnext types, as well as react for jsx. Adjust according to your needs.

Continuous Integration

GitHub Actions

Two actions are added by default:

• main which installs deps w/ cache, lints, tests, and builds on all pushes against a Node and OS matrix
• size which comments cost comparison of your library on every pull request using size-limit

Optimizations

Please see the main tsdx optimizations docs. In particular, know that you can take advantage of development-only optimizations:

// ./types/index.d.ts
declare var __DEV__: boolean;

// inside your code...
if (__DEV__) {
  console.log("foo");
}

You can also choose to install and use invariant and warning functions.

Module Formats

CJS, ESModules, and UMD module formats are supported.

The appropriate paths are configured in package.json and dist/index.js accordingly. Please report if any issues are found.

Named Exports

Per Palmer Group guidelines, always use named exports. Code split inside your React app instead of your React library.

Including Styles

There are many ways to ship styles, including with CSS-in-JS. TSDX has no opinion on this, configure how you like.

For vanilla CSS, you can include it at the root directory and add it to the files section in your package.json, so that it can be imported separately by your users and run through their bundler's loader.

Publishing to NPM

We recommend using np.