Fix slice expression type (#2009)

* Fix slice expression type (#1886)

The endIndex was not specified as an optional argument to the slice expression in the type. It does work in practice.

* Add changelog entry

* Add tests for slice expression

Fixes #1886
Builds on #1889

* Fix changelog

Co-authored-by: Leon <me@leonekmi.fr>

Author: kevinschaul

CHANGELOG.md

@@ -7,6 +7,7 @@
 - Fix issue [#1024](https://github.com/maplibre/maplibre-gl-js/pull/1024) - Zoom center not under cursor when terrain is on 
 - Fix errors when running style-spec bin scripts and added missing help. Removed unnecessary script 'gl-style-composite'. ([#1971](https://github.com/maplibre/maplibre-gl-js/pull/1971))
 - *...Add new stuff here...*
+- Fix the `slice` expression type ([#1886](https://github.com/maplibre/maplibre-gl-js/issues/1886))
 - 
 ## 3.0.0-pre.2
 

build/generate-style-spec.ts

@@ -176,7 +176,7 @@ export type ExpressionSpecification =
     | ['in', ExpressionInputType | ExpressionSpecification, ExpressionInputType | ExpressionSpecification]
     | ['index-of', ExpressionInputType | ExpressionSpecification, ExpressionInputType | ExpressionSpecification] // number
     | ['length', string | ExpressionSpecification]
-    | ['slice', string | ExpressionSpecification, number | ExpressionSpecification]
+    | ['slice', string | ExpressionSpecification, number | ExpressionSpecification, (number | ExpressionSpecification)?]
     // Decision
     | ['!', boolean | ExpressionSpecification] // boolean
     | ['!=', ExpressionInputType | ExpressionSpecification, ExpressionInputType | ExpressionSpecification, CollatorExpressionSpecification?] // boolean

src/style-spec/feature_filter/feature_filter.test.ts

@@ -44,6 +44,10 @@ describe('filter', () => {
         compileTimeCheck(['interpolate', ['linear'], ['line-progress'], 0, [10, 20, 30], 0.5, [20, 30, 40], 1, [30, 40, 80]]); // number array output!
         compileTimeCheck(['interpolate-hcl', ['linear'], ['line-progress'], 0, 'red', 0.5, 'green', 1, 'blue']);
         compileTimeCheck(['interpolate-lab', ['linear'], ['line-progress'], 0, 'red', 0.5, 'green', 1, 'blue']);
+        compileTimeCheck(['slice', 'myString', 0]);
+        compileTimeCheck(['slice', ['literal', [0]], 0]);
+        compileTimeCheck(['slice', 'myString', 0, 1]);
+        compileTimeCheck(['slice', ['literal', [0, 1, 2]], 0, 1]);
         compileTimeCheck(['step', ['get', 'point_count'], '#df2d43', 50, '#df2d43', 200, '#df2d43']);
         compileTimeCheck(['step', ['get', 'point_count'], 20, 50, 30, 200, 40]);
         compileTimeCheck(['step', ['get', 'point_count'], 0.6, 50, 0.7, 200, 0.8]);