Value.Clean inconsistent behavior with Type.Codec and Type.Union

[joshuaavalon]

I was writing code using Type.Codec for serializing json request and response.
However, I found out under some cases, Value.Clean is not removing the value when it is using with Type.Codec and Type.Union.

In the example code, I expect schema3 and schema4 should return the same values.

Example Code

import { Type } from "typebox";
import { Compile } from "typebox/compile";

const schema1 = Type.Codec(Type.String()).Decode(s => Number.parseInt(s)).Encode(s => s.toString());
const schema2 = Type.Options(Type.Object({ a: Type.Ref("schema1") }), { $id: "schema2" });
const schema3 = Type.Object({ data: Type.Union([Type.Ref("schema2"), Type.Null()]) });
const schema4 = Type.Object({ data: Type.Ref("schema2") });

function main(): void {
  const a1 = Compile({ schema1, schema2 }, schema3);
  console.log(a1.Clean({ data: { a: 1, b: 2 } })); // { data: { a: 1, b: 2 } }

  const a2 = Compile({ schema1, schema2 }, schema4);
  console.log(a2.Clean({ data: { a: 1, b: 2 } })); // { data: { a: 1 } }
}

main();

Version

typebox: 1.0.61

[joshuaavalon]

After some more investigation, I think the problem is caused by the following lines

typebox/src/value/codec/from-union.ts

Lines 56 to 63 in 05a360d

	function Encode(direction: string, context: TProperties, type: TUnion, value: unknown): unknown {
	let exterior = Callback(direction, context, type, value)
	for (const schema of type.anyOf) {
	const variant = FromType(direction, context, schema, Clone(exterior))
	if(!Check(context, schema, variant)) continue
	return variant
	}
	return exterior

It seems to related to #1477 .