node:buffer: Buffer backing properties are missing on Buffer instances

[andrewtdiz]

Summary

Node Buffer instances expose typed-array-style backing properties such as .buffer, .byteOffset, and legacy .parent. Perry's Buffer byte APIs pass the granular suite, but these backing properties currently diverge.

Node Behavior

./run_parity_tests.sh --filter test_parity_buffer exercises:

const ip = Buffer.from([0x10, 0x20, 0x30]);
console.log("buf.buffer instanceof ArrayBuffer:", ip.buffer instanceof ArrayBuffer);

const ipSlow = Buffer.allocUnsafeSlow(4);
ipSlow.fill(0);
console.log("buf.byteOffset (slow):", ipSlow.byteOffset);
console.log("buf.parent typeof:", typeof ipSlow.parent);

Node output:

buf.buffer instanceof ArrayBuffer: true
buf.byteOffset (slow): 0
buf.parent typeof: object

Perry Behavior

The same targeted parity run currently reports:

buf.buffer instanceof ArrayBuffer: false
buf.byteOffset (slow): undefined
buf.parent typeof: undefined

The granular ./run_parity_tests.sh --suite node-suite --module buffer run passed 124/124, so the bytes, reads/writes, encoding, search, and slice/subarray behavior are healthy. This gap is specifically the Buffer instance backing-property surface.

Suggested PR Cut

Batch this with related issues in:
node:buffer: module namespace and backing property parity cut

Good batch candidates:

• the leaf for namespace-bound Blob/File constructors

Do not batch with:

• unrelated Buffer byte/numeric API work
• Blob/File constructor coercion behavior unless touching the same module-property lowering path
• ArrayBuffer/DataView rewrites beyond the backing object needed for Buffer parity

Acceptance

• parity/regression test proves Buffer.from(...).buffer instanceof ArrayBuffer matches Node
• parity/regression test proves Buffer.allocUnsafeSlow(...).byteOffset matches Node for the deterministic slow-buffer case
• parity/regression test covers legacy parent shape at least to Node's observable typeof level
• existing granular buffer suite remains green
• related known-failure/docs/manifest entries updated if touched

[andrewtdiz]

Grouped for implementation in #3387 (node:buffer: module namespace and backing property parity cut).

[andrewtdiz]

I am taking this as part of the node:buffer namespace/backing-property PR cut tracked in #3387, together with #3385. The intended scope is Buffer .buffer, .byteOffset, and .parent parity plus the namespace-bound Blob/File constructor path.

[andrewtdiz]

Opened PR #3403 for this.

It wires Buffer .buffer, legacy .parent, and view byteOffset property reads through the registered-buffer property paths, with focused node-suite coverage. Verification is in the PR body.

[andrewtdiz]

PR opened: #3409