fix(fetch): re-add support for node v16.8.0+

[KhafraDev]

Fetch support incorrectly claimed it would work on node >= v16.5.0.

• Data urls would not work until v16.7.0 (requires URL.createObjectURL).
• Body could be infinitely consumed until v16.8.0 (requires stream.isDisturbed).
• DOMException has some issues where it would extend a TypeError (or at least its name property would be "TypeError")? No idea when this was fixed.

See #1526 (specifically this comment) for more context.

Also adds node v16.8.0 to the test matrix.

[codecov-commenter]

Codecov Report

Merging #1534 (cce41f1) into main (c1a0490) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1534   +/-   ##
=======================================
  Coverage   94.90%   94.90%           
=======================================
  Files          50       50           
  Lines        4608     4609    +1     
=======================================
+ Hits         4373     4374    +1     
  Misses        235      235           

Impacted Files	Coverage Δ
lib/fetch/constants.js	100.00% <ø> (ø)
index.js	100.00% <100.00%> (ø)
lib/core/request.js	100.00% <100.00%> (ø)
lib/fetch/body.js	98.51% <100.00%> (-0.02%)	⬇️
lib/fetch/util.js	82.35% <100.00%> (+0.17%)	⬆️
lib/fetch/webidl.js	98.29% <100.00%> (+<0.01%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c1a0490...cce41f1. Read the comment docs.

[KhafraDev]

@ronag - isDisturbed doesn't seem to work on node v16.5 (stream.isDisturbed doesn't yet exist)

undici/lib/core/util.js

Line 295 in c1a0490

function isDisturbed (body) {

edit: minimal repro (this should throw a TypeError)

import { fetch } from './index.js'

const controller = new AbortController()
const res = await fetch('https://www.google.com', {
  signal: controller.signal
})

controller.abort()

await res.text()

[mcollina]

lgtm

[mcollina]

I don't think we can do without isDisturbed, have you tried lifting the code from core? If not we'd have to support a version that at least has that.

[KhafraDev]

The code is mostly similar to core other than core checks if a symbol is true on the object and does a stream.readableAborted check (which didn't fix the issue). This is a really niche issue afaict, and only happens on versions that don't have stream.isDisturbed.

https://github.com/nodejs/node/blob/5fad0b93667ffc6e4def52996b9529ac99b26319/lib/internal/streams/utils.js#L245-L250

undici/lib/core/util.js

Lines 295 to 304 in c1a0490

	function isDisturbed (body) {
	return !!(body && (
	stream.isDisturbed
	? stream.isDisturbed(body) || body[kBodyUsed] // TODO (fix): Why is body[kBodyUsed] needed?
	: body[kBodyUsed] ||
	body.readableDidRead ||
	(body._readableState && body._readableState.dataEmitted) ||
	isReadableAborted(body)
	))
	}

[mcollina]

That's why we added it in core. You can't implement fetch() with only the public API from WHATWG streams. That Symbol expose some internal state.

[KhafraDev]

There were a few existing issues with node v16.5 that make fetch largely incompatible.

1. URL.createObjectURL was added in 16.7. Without it, fetching any date: url would fail.
2. When a request was aborted, it would throw a TypeError instead of a DOMException (?).
3. The isDisturbed util didn't work properly on this version.

edit: node-fetch test is still failing. Didn't experience this issue locally...

[mcollina]

Why did you close this?

[KhafraDev]

Didn't realize lol. Need to bump the min version for fetch to 16.8.

[mcollina]

lgtm