warn if invalid 'before' argument is passed to Map#addLayer

mapbox · Oct 4, 2017 · 2371f4e · 2371f4e
1 parent 64e9841
commit 2371f4e
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Showing 2 changed files with 26 additions and 1 deletion.
diff --git a/src/style/style.js b/src/style/style.js
@@ -568,7 +568,10 @@ class Style extends Evented {
 
         layer.setEventedParent(this, {layer: {id: id}});
 
-        const index = before ? this._order.indexOf(before) : this._order.length;
+        const beforeIndex = before ? this._order.indexOf(before) : null;
+        const index = before && beforeIndex !== -1 ? beforeIndex : this._order.length;
+        if (before && beforeIndex === -1) util.warnOnce(`Layer with id "${before}" does not exist on this map. Adding layer to the top of the stack.`);
+
         this._order.splice(index, 0, id);
 
         this._layers[id] = layer;

diff --git a/test/unit/style/style.test.js b/test/unit/style/style.test.js
@@ -1006,6 +1006,28 @@ test('Style#addLayer', (t) => {
         });
     });
 
+    t.test('warns if before layer does not exist', (t) => {
+        const style = new Style(new StubMap());
+        style.loadJSON(createStyleJSON({
+            layers: [{
+                id: 'a',
+                type: 'background'
+            }, {
+                id: 'b',
+                type: 'background'
+            }]
+        }));
+        const layer = {id: 'c', type: 'background'};
+        t.stub(util, 'warnOnce');
+
+        style.on('style.load', () => {
+            style.addLayer(layer, 'z');
+            t.deepEqual(style._order, ['a', 'b', 'c']);
+            t.ok(util.warnOnce.calledOnce);
+            t.end();
+        });
+    });
+
     t.test('fires an error on non-existant source layer', (t) => {
         const style = new Style(new StubMap());
         style.loadJSON(util.extend(createStyleJSON(), {