Tweak - Use strings instead of strings parsed to projection arrays

[birkskyum]

@HarelM

There's still no interpolate-projection, but this small extension to your work makes the:

  "interpolate",
      [
        "linear"
      ],
      [
        "zoom"
      ],
      8,
      ["vertical-perspective","vertical-perspective",1],
      10,
      ["mercator","mercator",1]

Into this, which I find is a lot cleaner:

  "interpolate",
      [
        "linear"
      ],
      [
        "zoom"
      ],
      8,
      "vertical-perspective",
      10,
      "mercator"

For some reason, I just can't see why it's better for the API to use ["vertical-perspective","vertical-perspective",1] to describe the zoom stops, when the last element is ignored, and the other duplicated.

Just to double-check, do you prefer the arrays, even though they hold no additional information than a primitive string?

Launch Checklist

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Link to related issues.
• Include before/after visuals or gifs if this PR includes visual changes.
• Write tests for all new functionality.
• Document any changes to public APIs.
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• Add an entry to CHANGELOG.md under the ## main section.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.56%. Comparing base (6ac2725) to head (3f642e3).

Files with missing lines	Patch %	Lines
src/expression/index.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                            Coverage Diff                             @@
##           interpolate-expression-with-projection     #902      +/-   ##
==========================================================================
- Coverage                                   92.62%   92.56%   -0.07%     
==========================================================================
  Files                                         107      107              
  Lines                                        4761     4761              
  Branches                                     1352     1352              
==========================================================================
- Hits                                         4410     4407       -3     
- Misses                                        351      354       +3     

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[HarelM]

Does this mean literal is no longer supported?

[birkskyum]

Yes, it makes very little sense to me why we want to support literals representing the transition from one transition to the other, unless we want to support transitions between intermediates (which I don't consider particularly useful - I've yet to think of a use):

5,
["vertical-perspective", "mercator", 0.2],
 10,
["equal-earth", "utm23", 0.5]

[HarelM]

Fair enough.

[HarelM]

I don't prefer the array, I just think it makes sense to support them, isn't it?