omit a warning if maxzoom <= clusterMaxZoom for geojson sources (#4604)

* omit a warning if maxzoom <= clusterMaxZoom for geojson sources

* fix lint issues

* CHANGELOG entry

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### ✨ Features and improvements
 - Support multiple layers in `map.on`, `map.once` and `map.off` methods ([#4279](https://github.com/maplibre/maplibre-gl-js/pull/4401))
+- Ensure GeoJSON cluster sources emit a console warning if `maxzoom` is less than or equal to `clusterMaxZoom` since in this case you may see unexpected results. ([#4604](https://github.com/maplibre/maplibre-gl-js/pull/4604))
 - _...Add new stuff here..._
 
 ### 🐞 Bug fixes

src/source/geojson_source.test.ts

@@ -55,6 +55,25 @@ const hawkHill = {
     }]
 } as GeoJSON.GeoJSON;
 
+describe('GeoJSONSource#constructor', () => {
+    const mapStub = {
+        _requestManager: {
+            transformRequest: (url) => { return {url}; }
+        }
+    } as any;
+    test('warn if maxzoom <= clusterMaxZoom', () => {
+        const warn = jest.spyOn(console, 'warn').mockImplementation(() => {});
+
+        const source = new GeoJSONSource('id', {data: hawkHill, maxzoom: 4, clusterMaxZoom: 4} as GeoJSONSourceOptions, mockDispatcher, undefined);
+        source.map = mapStub;
+        source.load();
+
+        expect(warn).toHaveBeenCalledWith('The maxzoom value "4" is expected to be greater than the clusterMaxZoom value "4".');
+
+        warn.mockRestore();
+    });
+});
+
 describe('GeoJSONSource#setData', () => {
     function createSource(opts?) {
         opts = opts || {};

src/source/geojson_source.ts

@@ -1,6 +1,6 @@
 import {Event, ErrorEvent, Evented} from '../util/evented';
 
-import {extend} from '../util/util';
+import {extend, warnOnce} from '../util/util';
 import {EXTENT} from '../data/extent';
 import {ResourceType} from '../util/request_manager';
 import {browser} from '../util/browser';
@@ -158,6 +158,10 @@ export class GeoJSONSource extends Evented implements Source {
 
         const scale = EXTENT / this.tileSize;
 
+        if (options.clusterMaxZoom !== undefined && this.maxzoom <= options.clusterMaxZoom) {
+            warnOnce(`The maxzoom value "${this.maxzoom}" is expected to be greater than the clusterMaxZoom value "${options.clusterMaxZoom}".`);
+        }
+
         // sent to the worker, along with `url: ...` or `data: literal geojson`,
         // so that it can load/parse/index the geojson data
         // extending with `options.workerOptions` helps to make it easy for