Fix issues with enum options filtering logic in enum_ function

[ikeyan]

The current implementation of the enum_ function in Valibot filters enum options using the following code:

valibot/library/src/schemas/enum/enum.ts

Lines 92 to 98 in 8ab047f

	export function enum_(
	enum__: Enum,
	message?: ErrorMessage<EnumIssue>
	): EnumSchema<Enum, ErrorMessage<EnumIssue> | undefined> {
	const options = Object.entries(enum__)
	.filter(([key]) => isNaN(+key))
	.map(([, value]) => value);

The purpose of this filtering logic is to remove the reverse mapping entries that TypeScript adds when transpiling enums. Specifically, when an enum member is defined as Name = value and value is a number, TypeScript generates a reverse mapping in the form Enum[value] = 'Name'. The key of this reverse mapping is stringified by Number.prototype.toString with radix=10 via ToPropertyKey as defined by the ECMAScript specification.

There are several issues with using +key and isNaN in the filtering logic:

• String Conversion: The +key operation follows the StringToNumber abstract operation as defined in the ECMAScript specification. Since enum_ filters out any number, this operation has several implications:

  • It trims leading and/or trailing whitespaces or line terminators.
  • If the string is empty after trimming, it returns 0.
  • Strings such as Infinity or -Infinity are interpreted as their respective number representations.
  • It interprets prefixes like 0b, 0o, or 0x as binary, octal, or hexadecimal literals.
  • Decimal variations such as 0.1, .1, and 0. are all valid and yield the respective numeric values.
  • It also allows leading zeros.
  • It accepts the + symbol as a valid sign.

• NaN Values in Enum: If the enum contains NaN, as in the following example:

  enum N { X = NaN }
  // equivalent to js: const N = { X: NaN, NaN: 'X' }

  The isNaN check will not work as expected since isNaN(key) will return true when key is 'NaN', causing the 'NaN' key to be retained rather than filtered out.

To correctly filter out these reverse mappings, I made the filtering logic more precise. In this PR, rather than isNaN, the parsed value is stringified and is matched against the original key. If it matches, it is filtered out.

Additionally, the filtering logic is not reflected in the EnumSchema type. For example, when using enum_({ 1: "A" }), the options end up being empty, which was not obvious until runtime. Therefore I implemented type-level option filtering.