oven-sh/bun

Support `ReadableStream.from()`

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#3700 opened on Jul 20, 2023

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 (9 comments) (11 reactions) (0 assignees)Rust (90,348 stars) (4,486 forks)batch import
enhancementgood first issueweb-api

Description

What is the problem this feature would solve?

Creating a ReadableStream from an array (or any other iterable) requires a lot of boilerplate, as can be seen in these tests and this example.

What is the feature you are proposing to solve the problem?

The Streams standard now has a new utility method ReadableStream.from(asyncIterable), which adapts any sync or async iterable into a ReadableStream. Once Bun supports this method, creating a ReadableStream from an array would become a one-liner.

Specification: https://streams.spec.whatwg.org/#rs-from Spec change: https://github.com/whatwg/streams/pull/1083 WPT tests: https://github.com/web-platform-tests/wpt/pull/27009

Deno and Node.js also recently implemented this new method, see https://github.com/denoland/deno/pull/19446 and https://github.com/nodejs/node/pull/48395.

Since Bun is powered by JavaScriptCore, you may also want to look into their pull request: https://github.com/WebKit/WebKit/pull/12454

What alternatives have you considered?

No response

Contributor guide

Tech stack
javascriptnodejs
Domain
backenddeveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaScriptWeb Streams APIBun internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Examine the specification for `ReadableStream.from()` at the WHATWG Streams standard. Review the Deno and Node.js implementations linked in the issue for reference patterns. Since Bun uses JavaScriptCore, investigate the WebKit pull request to understand any engine specific changes needed. Also look at the WPT tests to ensure compliance. The feature is documented in the issue with clear examples and references to existing code in Bun's test suite.