Fix #12689 - Remove unnecessary src=null on WMS tile load error

web/client/components/map/openlayers/__tests__/Layer-test.jsx

@@ -357,6 +357,40 @@ describe('Openlayers layer', () => {
             }, 200);
         });
     });
+    it('render wms singleTile layer with error does not request a spurious "null" url', (done) => {
+        mockAxios.onGet().reply(r => {
+            expect(r.url.indexOf('SAMPLE_URL') >= 0 ).toBeTruthy();
+            return [200, "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
+            "<ows:ExceptionReport xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\">\n" +
+            "  <ows:Exception exceptionCode=\"InvalidParameterValue\" locator=\"srsname\">\n" +
+            "    <ows:ExceptionText>msWFSGetFeature(): WFS server error. Invalid GetFeature Request</ows:ExceptionText>\n" +
+            "  </ows:Exception>\n" +
+            "</ows:ExceptionReport>"];
+        });
+        const options = {
+            type: 'wms',
+            visibility: true,
+            singleTile: true,
+            url: 'SAMPLE_URL',
+            name: 'osm:vector_tile'
+        };
+        const layer = ReactDOM.render(<OpenlayersLayer
+            type="wms"
+            options={{
+                ...options
+            }}
+            map={map} />, document.getElementById("container"));
+        expect(layer.layer.getSource()).toBeTruthy();
+        layer.layer.getSource().on('imageloaderror', (e) => {
+            setTimeout(() => {
+                // the error handler must not set img.src = null, which the DOM coerces
+                // to the literal string "null" and resolves into a spurious request
+                const img = e.image.getImage();
+                expect(img.getAttribute('src') === 'null' || (img.src || '').endsWith('/null')).toBe(false);
+                done();
+            }, 200);
+        });
+    });
     it('creates a tiled wms layer for openlayers map with long url', (done) => {
         let options = {
             "type": "wms",

web/client/components/map/openlayers/plugins/WMSLayer.js

@@ -96,8 +96,7 @@ const loadFunction = (options, headers) => function(image, src) {
                         throw new Error(response.dataText);
                     }
                 }).catch(errorMessage => {
-                    image.getImage().src = null;   // needed to trigger the MS imageloaderror event in Map.onLayerError
-                    image.setState(3);            // set error state for tile and removed from the queue to prevent reloading loops
+                    image.setState(3);            // set error state for tile; this alone fires the source's tileloaderror/imageloaderror (state-based, no DOM event needed) and removes it from the queue to prevent reloading loops
                     failTiles.add(src);           // indexing fail url tile to prevent reloading loops
                     console.error(errorMessage);  // show ogc exception in console for debugging
                 });