SassCalculation.clamp with less than 3 arguments fail the validation

[ntkme]

https://sass-lang.com/documentation/js-api/classes/sasscalculation/#clamp

clamp(min: CalculationValue, value?: CalculationValue, max?: CalculationValue): SassCalculation

In JS API, we can construct clamp with only 1 one argument.

In Dart code documentation:

  /// This may be passed fewer than three arguments, but only if one of the
  /// arguments is an unquoted `var()` string.

Then, this spec seems wrong to throw an error for requiring 3 arguments: https://github.com/sass/sass-spec/blob/e6e6762153c8c6a02d289ab078fb1186c10b91f3/js-api-spec/value/calculation.test.ts#L320-L327

Finally in dart-sass and embedded-host-node, there are extra logic in protofy and deprotofy to enforce 3 arguments:

dart-sass/lib/src/embedded/protofier.dart

Lines 352 to 362 in 6c59213

	} else if (calculation.name == "clamp") {
	if (calculation.arguments.length != 3) {
	throw paramsError(
	"Value.Calculation.arguments must have exactly 3 arguments for "
	"clamp().");
	}
	return SassCalculation.clamp(
	_deprotofyCalculationValue(calculation.arguments[0]),
	_deprotofyCalculationValue(calculation.arguments[1]),
	_deprotofyCalculationValue(calculation.arguments[2]));

https://github.com/sass/embedded-host-node/blob/2b1f4ecaf83a9e949976427f522291f674a04a57/lib/src/protofier.ts#L383-L387

These currently makes it impossible to return a clamp with an unquoted var() string in custom functions.

[nex3]

The _verifyLength() call is correct—that function does include logic to add exceptions for var() calls. The verification logic in the protofier and the JS API tests are indeed wrong, though.