webstreams: accept ArrayBuffer in WritableStream write sink

[suuuuuuminnnnnn]

Per the WHATWG Compression Streams spec, CompressionStream and
DecompressionStream must accept BufferSource
(ArrayBuffer | ArrayBufferView) as valid chunk types.

Currently, writing a plain ArrayBuffer to the writable side throws
ERR_INVALID_ARG_TYPE, because the adapter in
newWritableStreamFromStreamWritable passes chunks directly to
stream.write(), which only accepts ArrayBufferView types.

This change normalizes plain ArrayBuffer chunks to a Uint8Array view
before forwarding them to the underlying Node.js stream.

Changes included:

• normalize ArrayBuffer to Uint8Array in lib/internal/webstreams/adapters.js
• add a regression test for ArrayBuffer input
• unskip the relevant WPT compression BufferSource test (if passing)

Fixes: #43433

[nodejs-github-bot]

Review requested:

• @nodejs/web-standards

[Renegade334]

Nit: Similar to Mattias's comment, this iteration doesn't need to be done manually:

Suggested change

	const chunks = [];
	let done = false;
	while (!done) {
	const { value, done: d } = await reader.read();
	if (value) chunks.push(value);
	done = d;
	}
	const chunks = await Array.fromAsync(ds.readable);

[MattiasBuelens]

@suuuuuuminnnnnn Please take a look 🙂

[suuuuuuminnnnnn]

Good catch, thanks both — I'll apply this suggestion too.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.75%. Comparing base (ae2ffce) to head (aa1901c).
⚠️ Report is 105 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61913      +/-   ##
==========================================
- Coverage   89.75%   89.75%   -0.01%     
==========================================
  Files         674      674              
  Lines      204416   204893     +477     
  Branches    39285    39377      +92     
==========================================
+ Hits       183472   183892     +420     
- Misses      13227    13283      +56     
- Partials     7717     7718       +1     

Files with missing lines	Coverage Δ
lib/internal/webstreams/adapters.js	85.75% <100.00%> (+0.17%)	⬆️

... and 81 files with indirect coverage changes

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[suuuuuuminnnnnn]

Thanks @MattiasBuelens and @Renegade334 — applied both suggestions.

• added the object mode guard before normalizing ArrayBuffer
• replaced the manual read loop with Array.fromAsync(...)
• replaced the manual piping/write loop with await cs.readable.pipeTo(ds.writable)

I kept the PR scoped to the ArrayBuffer handling fix + regression coverage.
Appreciate the review.

[github-actions]

Failed to start CI

   ⚠  No approving reviews found
   ✘  Refusing to run CI on potentially unsafe PR

https://github.com/nodejs/node/actions/runs/22255119973

[mcollina]

lgtm

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/71388/

[MattiasBuelens]

Nit-pick: you could also use Array.fromAsync here. 😉

[suuuuuuminnnnnn]

Done, applied to both tests. Thanks!