mapbox / mapbox/mapbox-maps-ios

Handling Expression empty arrays

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auto-triaged bug :beetle: feature :green_apple:
Dominant language
Swift
Stars
601
Forks
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PR merge metrics
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Description

## Environment

- Xcode version: 14.3.1
- Maps SDK Version: 10.15.0

## Observed behavior and steps to reproduce

It has always been a nightmare to manage match expressions with arrays, which could be empty (which leads to a crash with an error "**Expected at least one branch label**").

Now, when there's a "type safe"`Exp`, it became even harder (while overall `Exp` has much better usage), since there's no instrument to create `Exp` dynamically in any means. E.g. allowing closures inside it:

Error: Trailing closure passed to parameter of type '[Expression.Argument]' that does not accept a closure

```
let expression = Exp(.match) {
Exp(.get) { "objectId" }

if !yellowObjectIds.isEmpty {
yellowObjectIds
UIColor.yellow
}

blueObjectIds
UIColor.blue

UIColor.white
}
```

## Expected behavior

Ideally, it would be useful to cover such cases inside wrapped `Exp`, so there would be no struggle. Or at least have any instrument of dynamic creation of `Exp`

## Notes / preliminary analysis

Maybe there are already some instruments to cover my case, which I couldn't find in documentation. I would be very grateful, if somebody points me in the right direction.

## Additional links and references

I found an [old issue](https://github.com/mapbox/mapbox-gl-js/issues/7895) in js repo about the same problem, but before `Exp` were introduces

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  4. Open a pull request that references the issue number.

Research direction

The issue names no source file or test; begin with the type-safe Exp(.match) API and reproduce the empty-array case on Xcode 14.3.1 with Maps SDK 10.15.0. Done would require an agreed supported way to represent empty or dynamically built match branches, plus coverage or documentation for that behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
ios, swift
Domain
mobile
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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