Deno 2 has a broken API for node:v8 when using serialize with Float16Array

[cu8code]

Version: Deno 2.0.0

Here is an example code that I run

import { serialize } from "node:v8";

const float16Data = new Float16Array([1.0, 2.5, 3.14]);

try {
  const serialized = serialize(float16Data);
  console.log("Serialization successful!");
  console.log("Serialized data:", serialized);
} catch (error) {
  console.error("Serialization failed:", error.message);
}

I get the error

Serialization failed: Unserializable host object: 1,2.5,3.140625

[cu8code]

The error is only with Float16Array

import { serialize, deserialize } from "node:v8";

function testSerialization(description, value) {
  console.log(`\nTesting ${description}:`);
  try {
    const serialized = serialize(value);
    const deserialized = deserialize(serialized);
    console.log("✓ Serialization successful");
    console.log("Original:", value);
    console.log("Deserialized:", deserialized);
  } catch (error) {
    console.error("✗ Serialization failed:", error.message);
  }
}


const arrays = {
  "Float16Array": new Float16Array([1.0, 2.5, 3.14]),
  "Float32Array": new Float32Array([1.0, 2.5, 3.14]),
  "Float64Array": new Float64Array([1.0, 2.5, 3.14]),
  "Int32Array": new Int32Array([1, 2, 3]),
  "Uint8Array": new Uint8Array([1, 2, 3])
};

console.log("Deno version:", Deno.version.deno);
console.log("V8 version:", Deno.version.v8);

for (const [type, array] of Object.entries(arrays)) {
  testSerialization(type, array);
}


testSerialization("Regular Array", [1.0, 2.5, 3.14]);

I get the output which indicated only Float16Array is broken

Deno version: 2.0.0
V8 version: 12.9.202.13-rusty

Testing Float16Array:
✗ Serialization failed: Unserializable host object: 1,2.5,3.140625

Testing Float32Array:
✓ Serialization successful
Original: Float32Array(3) [ 1, 2.5, 3.140000104904175 ]
Deserialized: Float32Array(3) [ 1, 2.5, 3.140000104904175 ]

Testing Float64Array:
✓ Serialization successful
Original: Float64Array(3) [ 1, 2.5, 3.14 ]
Deserialized: Float64Array(3) [ 1, 2.5, 3.14 ]

Testing Int32Array:
✓ Serialization successful
Original: Int32Array(3) [ 1, 2, 3 ]
Deserialized: Int32Array(3) [ 1, 2, 3 ]

Testing Uint8Array:
✓ Serialization successful
Original: Uint8Array(3) [ 1, 2, 3 ]
Deserialized: Uint8Array(3) [ 1, 2, 3 ]

Testing Regular Array:
✓ Serialization successful
Original: [ 1, 2.5, 3.14 ]
Deserialized: [ 1, 2.5, 3.14 ]

[cu8code]

The error is occurring because, there is no support for Float16Array, in arrayBufferViewTypeToIndex function. I am not sure why ?

deno/ext/node/polyfills/v8.ts

Lines 215 to 231 in c314b2d

	function arrayBufferViewTypeToIndex(abView: ArrayBufferView) {
	const type = ObjectPrototypeToString(abView);
	if (type === "[object Int8Array]") return 0;
	if (type === "[object Uint8Array]") return 1;
	if (type === "[object Uint8ClampedArray]") return 2;
	if (type === "[object Int16Array]") return 3;
	if (type === "[object Uint16Array]") return 4;
	if (type === "[object Int32Array]") return 5;
	if (type === "[object Uint32Array]") return 6;
	if (type === "[object Float32Array]") return 7;
	if (type === "[object Float64Array]") return 8;
	if (type === "[object DataView]") return 9;
	// Index 10 is FastBuffer.
	if (type === "[object BigInt64Array]") return 11;
	if (type === "[object BigUint64Array]") return 12;
	return -1;
	}

deno/ext/node/polyfills/v8.ts

Lines 239 to 261 in c314b2d

	_writeHostObject(abView: any) {
	// Keep track of how to handle different ArrayBufferViews. The default
	// Serializer for Node does not use the V8 methods for serializing those
	// objects because Node's `Buffer` objects use pooled allocation in many
	// cases, and their underlying `ArrayBuffer`s would show up in the
	// serialization. Because a) those may contain sensitive data and the user
	// may not be aware of that and b) they are often much larger than the
	// `Buffer` itself, custom serialization is applied.
	let i = 10; // FastBuffer
	if (abView.constructor !== Buffer) {
	i = arrayBufferViewTypeToIndex(abView);
	if (i === -1) {
	throw new this._getDataCloneError(
	`Unserializable host object: ${abView}`,
	);
	}
	}
	this.writeUint32(i);
	this.writeUint32(abView.byteLength);
	this.writeRawBytes(
	new Uint8Array(abView.buffer, abView.byteOffset, abView.byteLength),
	);
	}

[bartlomieju]

FYI this doesn't work in Node.js either (v23.1) because Float16Array is not available in Node. This is not a "good first issue" after all. We'd need to wait for Node to implement it, or at least coordinate with them to ensure that we use correct number for the this type.

[bartlomieju]

The support for serde of Float16Array was landed in Node.js in nodejs/node#55996, PR to Deno will follow.