node:stream: implement real Node/WHATWG stream adapters

[andrewtdiz]

Summary

Perry exposes the classic node:stream Web-stream adapter methods, but they currently return shape stubs rather than real adapters. This is separate from #1545, which tracks the node:stream/web submodule constructors themselves.

Affected surface

• stream.Readable.fromWeb(readableStream[, options])
• stream.Readable.toWeb(streamReadable[, options])
• stream.Writable.fromWeb(writableStream[, options])
• stream.Writable.toWeb(streamWritable)
• stream.Duplex.fromWeb(pair[, options])
• stream.Duplex.toWeb(streamDuplex[, options])

Evidence

• Closed node:stream — implement Web-stream interop (Readable.toWeb/fromWeb, Writable.toWeb/fromWeb) #1540 made the helper names exist, but the current implementation still documents that real bidirectional adapters are tracked separately.
• js_node_stream_to_web returns a generic Web-stream-shaped object with both getReader and getWriter stubs; data is not forwarded between the Node and WHATWG stream universes (crates/perry-runtime/src/node_stream_constructors.rs:829-873).
• js_node_stream_from_web returns a fresh Duplex stub for either direction instead of adapting the supplied Web stream (crates/perry-runtime/src/node_stream_constructors.rs:876-881).
• docs/runtime-parity-gaps.md still lists the classic stream Web adapter APIs in the node:stream gap set (docs/runtime-parity-gaps.md:987-991).

Expected Node-compatible behavior

The adapters should bridge data, errors, close/cancel/abort behavior, and backpressure between Node classic streams and WHATWG streams. toWeb should return direction-correct Web stream objects, and fromWeb should expose Node stream instances that consume/produce data from the provided Web stream.

Duplicate check

Searched issues and PRs for stream fromWeb toWeb Web Stream interop and stream compose duplexPair fromWeb toWeb data. No open tracker was found. Closed #1540 covered helper presence/shape only; open #1545 covers the separate node:stream/web submodule constructors.

Verification note

I could not run a fresh local Perry parity probe in this workspace because there is no local perry binary. This issue is based on committed parity metadata and current source inspection.

[andrewtdiz]

Opened draft PR #4237: #4237

This implements deterministic data flow for all six static Node/WHATWG stream adapter helpers:

• Readable.toWeb / Readable.fromWeb
• Writable.toWeb / Writable.fromWeb
• Duplex.toWeb / Duplex.fromWeb

Validation:

• cargo fmt --all -- --check
• cargo check -p perry-runtime -p perry-stdlib -p perry-codegen
• git diff --check
• Direct Perry runs for all six stream/webstream parity fixtures pass

Known follow-up: richer cancel/error/abort/backpressure parity is still intentionally left for later work; this PR unblocks real bridge objects and deterministic chunk flow instead of shape-only stubs.

[andrewtdiz]

PR #4237 merged on June 3, 2026 and implemented the deterministic Node/WHATWG stream adapter data-flow slice for this issue:

• Readable.toWeb / Readable.fromWeb
• Writable.toWeb / Writable.fromWeb
• Duplex.toWeb / Duplex.fromWeb

Validation from the merged PR included direct Perry runs for all six stream/webstream parity fixtures, plus cargo check, cargo fmt, git diff --check, and the file-size gate. This issue looks stale-open and ready for maintainer closure, with richer cancel/error/abort/backpressure behavior left to separate follow-ups.

[andrewtdiz]

Current main still has a narrow node:stream static value-read gap: class static helper calls are implemented, but property reads/captured references for Readable.from/fromWeb/toWeb/isDisturbed/isErrored, Writable.fromWeb/toWeb/isDisturbed/isErrored, and the inherited Duplex/Transform/PassThrough statics return undefined. I am opening a focused PR for that surface only; it does not change adapter data flow, cancel/error/backpressure behavior, or the separate stream iterator-helper hang.

[andrewtdiz]

Opened draft PR #4346 for the remaining static value-read slice: #4346

Validated against a Node 26 oracle and Perry no-auto output for test-parity/node-suite/stream/static/class-static-exports.ts, plus the focused runtime unit, runtime/stdlib debug build, formatter check, and whitespace check. This PR is intentionally scoped to constructor static property values/captured references and does not claim the broader adapter-data-flow follow-ups.