fix(themes): Highlight .token.null

[ExE-Boss]

The JSON syntax highlighting uses .token.null to style null:

prism/components/prism-json.js

Line 15 in 4362e42

'null': /\bnull\b/

This updates the Prism stylesheet to style it using the style for .token.boolean and .token.number.

[mAAdhaTTah]

It seems curious that JSON is the only language that has .token.null for null. I think we highlight it as a keyword in other languages. Might make more sense to change how we highlight in JSON.

@RunDevelopment Thoughts?

[ExE-Boss]

Well, PHP used .token.null at one point too:

prism/components/prism-php.js

Lines 53 to 58 in c5160a1

	Prism.languages.insertBefore('php', 'class-name', {
	'null': {
	pattern: /\b(?:null)\b/i,
	alias: 'constant predefined-constant'
	}
	});

And there might be other languages that do the same.

[RunDevelopment]

At this point in time, the only languages which have a null token without aliases are JSON and SCSS.

I think we highlight it as a keyword in other languages.

Depends on the language. Most use keyword, some use boolean, few use others.

Might make more sense to change how we highlight in JSON.

I also think it's better for JSON to have null as a keyword instead of changing the themes to include null for a few reasons:

1. You only have to change one file. keyword is supported by all themes.
2. JS uses keyword for null and JSON is supposed to be a subset of JS (it's not, but almost).
3. We can always use the Highlight Keywords plugin to change the style of null.

[ExE-Boss]

2. JS uses keyword for null and JSON is supposed to be a subset of JS (it's not, but almost).

It is a subset of ES2019+, as ES2019 now allows unescaped \u2028 and \u2029 in strings:

let str = "a
b"; // This string contains an unescaped Line Separator

---

That said, I’d still like to fix highlighting of .token.null.

[RunDevelopment]

That said, I’d still like to fix highlighting of .token.null.

.token.null is pretty much a non-standard token name, so I think it's ok to ignore it.
Plus, changing JSON and SCSS is simply easier.

[mAAdhaTTah]

Agreed. I'd prefer to use a token we reuse across a lot of languages than handling a token used once or twice in a theme. I find it a little curious some of them are using boolean for null; keyword seems to make the most sense, so maybe we just decide now to consistently use keyword for it?

Appreciate you raising this to our attention!

[RunDevelopment]

keyword seems to make the most sense, so maybe we just decide now to consistently use keyword for it?

Well, it's not that easy...
Most languages in which null (so similar) is a language construct highlight it as keyword. But we can't just make null a keyword in all languages.
I.e. in C/C++ NULL is a macro, in PHP it's a constant.

But I think that null (or conceptually similar) should not be boolean as in Python (None), SQL, and Twig.

[mAAdhaTTah]

Fair enough; choosing something that makes sense for each language is fine. I'm admittedly less familiar with those languages, but I think a null token for JSON & SCSSS only doesn't really make sense. So we should update the JSON + SCSS languages to give null different tokens. Agree?

[ExE-Boss]

I dunno, the null token makes a lot of sense for JSON, maybe we could add keyword as an alias?

[RunDevelopment]

So we should update the JSON + SCSS languages to give null different tokens. Agree?

Maybe the alias idea from @ExE-Boss is even better. I mean, we used these token names for quite some time now, so there might be some folks out there how incorporated null into their themes. With an alias, it's unlikely (but still possible) that we break them.

[mAAdhaTTah]

I'm on board with that.

[RunDevelopment]

Just for clarification: We are not going to change the themes now, are we? @ExE-Boss @mAAdhaTTah

[ExE-Boss]

I’d like to fix the themes.

[RunDevelopment]

@ExE-Boss With or without the aliases? Because after the aliases, there's nothing to fix.

[ExE-Boss]

Well, even with the aliases, .token.null should still take precedence over .token.keyword.

[RunDevelopment]

So you want to change the look of null to be highlighted the different from keyword, I suppose.
I think is better if JSON's nulls are highlighted like JS's nulls. Consistency.

[RunDevelopment]

I feel like this question should have been asked a lot sooner, but why do you want null to look like boolean?
Null and true/false are not conceptually close (IMO) and most editors highlight both like keywords, so why boolean?

[ExE-Boss]

After a day of thinking it over, I think it might be better to just highlight it using keyword as an alias.

[mAAdhaTTah]

I'm personally opposed to changing the theme here, as I think handling a token in all the themes that only appears in two languages is unnecessary and the correct fix is the keyword change, as suggested.

[RunDevelopment]

I'm personally opposed to changing the theme here

Agreed. After #1735 there's nothing left to fix.

I'm closing this now. Feel free to reopen this if further discussion is necessary.