node:buffer: namespace-bound Blob and File constructors lose native behavior

[andrewtdiz]

Summary

node:buffer should expose Blob and File as usable constructor values on the module namespace object. Perry supports direct named/global constructor forms, but namespace-bound constructor values lose native Blob/File behavior.

Node Behavior

./run_parity_tests.sh --filter test_parity_buffer exercises the namespace form:

import * as buffer from "node:buffer";

const BlobCtor: any = (buffer as any).Blob;
const blob = new BlobCtor(["hello"]);
console.log("Blob size:", blob.size);
console.log("Blob text:", await blob.text());

const FileCtor: any = (buffer as any).File;
const f = new FileCtor(["hello"], "greeting.txt", { lastModified: 1700000000000 });
console.log("File.name:", f.name);
console.log("File.lastModified:", f.lastModified);

Node output includes:

Blob size: 5
Blob text: hello
File.name: greeting.txt
File.lastModified: 1700000000000

Perry Behavior

The same targeted parity run currently reports test_parity_buffer as an output mismatch. The namespace-bound constructor section prints:

Blob size: <unsupported>
Blob text: <unsupported>
File.name: undefined
File.lastModified: undefined

The granular ./run_parity_tests.sh --suite node-suite --module buffer run passed 124/124, including direct import { Blob } / import { File } fixtures. That narrows this to namespace/dynamic constructor binding rather than the direct constructor runtime path.

Source evidence: direct new Blob(...) / new File(...) lowers through the built-in constructor arms in crates/perry-codegen/src/lower_call/builtin.rs. HIR tagging also recognizes direct named imports and selected globalThis.File forms in crates/perry-hir/src/destructuring/var_decl.rs, but a constructor value obtained through (buffer as any).Blob / (buffer as any).File is not preserved as the native Blob/File class identity.

Suggested PR Cut

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

Good batch candidates:

• node:buffer: coerce Blob and File constructor inputs like Node #2959
• the leaf for Buffer backing properties

Do not batch with:

• unrelated Buffer byte/numeric API work
• node:fs.openAsBlob() file-backed Blob support
• broad Blob/File coercion changes beyond constructor value exposure unless they are required by the same tests

Acceptance

• parity/regression test proves const BlobCtor = buffer.Blob; new BlobCtor([...]) behaves like Node
• parity/regression test proves const FileCtor = buffer.File; new FileCtor([...], name, opts) exposes Node-compatible name, lastModified, size, and text behavior
• existing direct named/global Blob/File fixtures continue passing
• 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 #3386. The intended scope is preserving namespace-bound Blob/File constructor behavior and adding focused Buffer backing-property parity tests/fixes.

[andrewtdiz]

Opened PR #3403 for this.

It adds node:buffer Blob namespace export coverage and lowers buffer.Blob / buffer.File constructor aliases through the existing fetch-backed classes. Verification is in the PR body.

[andrewtdiz]

PR opened: #3409