Add media-feature-range-context-notation

[jeddy3]

What is the problem you're trying to solve?

To write media features in a range context consistently when there are two media features of the same name.

What solution would you like to see?

A new rule to either combine or separate media features.

For example, either:

@media (width >= 500px) and (width <= 1200px) {}

Or:

@media (500px <= width <= 1200px) {}

• Name: media-feature-range-context-notation
• Primary option: "basic"|"nested"
• Secondary options: none
• Autofixable: Yes
• Message: Expected "${primary}" media feature range context notation
• Description: "Specify basic or nested notation for media features in range context (Autofixable)."
• Section: "Enforce conventions" -> "Notation"

Primary options names from spec:

The basic form, consisting of a feature name, a comparison operator, and a value, returns true if the relationship is true.

And:

The remaining forms, with the feature name nested between two value comparisons, returns true if both comparisons are true.

See #6497 (comment)

[ybiquitous]

Sounds good! 👍🏼

[Mouvedia]

The fix for this one will require advanced conversion of units for proper mergers.

e.g.
@media (width >= 500px) and (width < 50em) and (width <= 1200px) {} (16px font-size)
to
@media (500px <= width <= 1200px) {}

[jeddy3]

I may be wrong, but I don't think we can safely merge ems into px as people can change the initial value of font-size in their browser settings. For example, doubling it to 32px.

Either way, it's likely people will be using the same units across their media features so let's implement that first. This reminds me, I need to create an issue for media-feature-name-unit-allowed-list from #6211 (comment).

I've labelled the issue as ready to implement. Please consider contributing this rule if anyone has time.

There are steps on how to add a new rule in the Developer guide.

[Mouvedia]

so let's implement that first

same unit : the removal of useless conditions while merging is a first step
inconsistent units : the conversion—if possible—can be done later

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