oklch in @property doesn't accept `<number>`

[CrendKing]

See in Playground.

In <color_value>, the definition is

<oklch()> = oklch( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <hue> | none ] [ / [ <alpha-value> | none ] ]? )

which should accept a fractional number for the lightness and I do not see this differ when used in @property initial value. And it doesn't report error outside the @property:

--color: oklch(0.5 0 0)

However, as the initial value of @property, the following code

@property --why-this-not-work {
    syntax: "<color>";
    inherits: false;
    initial-value: oklch(0.5 0 0);
}

causes error /* ERROR: Unexpected token Function("oklch") */.

When I use the fractional number form, all browsers render the color without problem.

[CrendKing]

I believe this is the function responsible:

lightningcss/src/values/color.rs

Line 1139 in 496f4f6

let l = parser.parse_percentage(input)?.clamp(0.0, f32::MAX);

Should be parse_number_or_percentage(). And also applies to other color functions like lab.

[CrendKing]

Spent some time investigating why it doesn't error out outside @property. The parsing of the color function indeed failed with the same Err. However, on the outside, the TokenList::parse_into() has an else clause that parses the input into a general function with arguments. Meaning, the argument could be in any type or form and no error will happen. For example, one can write

:root {
    --color: oklch("Hello World" 0 0);
}

without error. Meanwhile this immediately generates error:

@property --color {
    syntax: "<color>";
    inherits: false;
    initial-value: oklch("Hello World" 0 0);
}

Is there particular reason why the rule is so lax?

[devongovett]

Duplicate of #809.

[CrendKing]

I don't think is duplicate of #809 since there is no mention of the specific behavior in @property. But the underlying cause is probably the same. Do you guys want to follow up on this issue? The code change seems pretty trivial on the surface (change a bunch of parse_percentage/parse_number to parse_number_or_percentage). I could try to make a PR if you want.

[devongovett]

It's not trivial. The spec changed in a breaking way unfortunately. See #465

[CrendKing]

I see. Thanks for the hard work and education. I wasn't aware of a spec change.