node:buffer: validate Blob object URL creation like Node

[andrewtdiz]

Summary

Node's Blob object URL surface rejects non-Blob inputs to URL.createObjectURL() and returns blob:nodedata:<uuid> identifiers for valid Blob values. Perry's object URL helper currently maps invalid handles to an empty string and generates monotonic 32-hex identifiers without UUID separators.

Node.js behavior

Observed with Node v25.9.0:

const { Blob, resolveObjectURL } = require("node:buffer");

URL.createObjectURL("x");
// TypeError ERR_INVALID_ARG_TYPE: The "obj" argument must be an instance of Blob

URL.createObjectURL({});
// TypeError ERR_INVALID_ARG_TYPE: The "obj" argument must be an instance of Blob

const b = new Blob(["hi"]);
const id = URL.createObjectURL(b);
console.log(id);
// blob:nodedata:<uuid>, e.g. blob:nodedata:50e4632e-6844-422a-b2d5-68227d49b179

console.log(resolveObjectURL(id)?.size); // 2
URL.revokeObjectURL(id);
console.log(resolveObjectURL(id));       // undefined

URL.revokeObjectURL(nonString) and resolveObjectURL(nonStringOrUnknown) are lenient and return undefined, but createObjectURL validates that the object is a Blob.

Current Perry behavior

crates/perry-stdlib/src/fetch_blob.rs implements the object URL registry:

• js_url_create_object_url(blob_handle) calls handle_id(blob_handle) and returns an empty string when the id is 0; it does not throw for strings, objects, or other non-Blob values.
• Valid ids are formatted with format!("blob:nodedata:{:032x}", n), so generated ids are monotonic fixed-width hex strings rather than Node's UUID-shaped blob:nodedata:<uuid> strings.
• resolveObjectURL/revokeObjectURL leniency broadly matches Node for bad or unknown URLs, so the validation gap is specific to creation.

Suggested test surface

• URL.createObjectURL("x") and URL.createObjectURL({}) throw TypeError with code ERR_INVALID_ARG_TYPE.
• URL.createObjectURL(new Blob(["hi"])) returns a string matching ^blob:nodedata:[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$.
• resolveObjectURL(id) returns a Blob with the original size/type, and returns undefined after revoke.
• revokeObjectURL(123) and resolveObjectURL(123) remain lenient.

Scope / non-goals

This is scoped to Blob object URL validation and identifier shape. It does not require changing Blob/File constructor coercion or object URL lifetime semantics beyond existing revoke behavior.

[andrewtdiz]

I'll take this one. I'll add parity coverage for createObjectURL validation and UUID-shaped ids, then update the Blob URL registry to reject non-Blob inputs while keeping revoke/resolve lenient.

[andrewtdiz]

Opened PR #3097 with Blob object URL validation and UUID-shaped IDs. The new fixture fails before the change (test-parity/reports/parity_report_20260530_060041.json) and the rebased Blob/File subset passes after (test-parity/reports/parity_report_20260530_061124.json).