getGetLegendRequestUrl accepts a LAYER parameter now

src/ol/source/ImageWMS.js

@@ -197,15 +197,15 @@ class ImageWMS extends ImageSource {
    *
    * @param {number} [resolution] Resolution. If set to undefined, `SCALE`
    *     will not be calculated and included in URL.
-   * @param {Object} [params] GetLegendGraphic params. Default `FORMAT` is
+   * @param {Object} [params] GetLegendGraphic params. If `LAYER` is set, the
-   *     `image/png`. `VERSION` should not be specified here.
+   *     request is generated for this wms layer, else it will try to use the
+   *     configured wms layer. Default `FORMAT` is `image/png`.
+   *     `VERSION` should not be specified here.
    * @return {string|undefined} GetLegendGraphic URL.
    * @api
    */
   getLegendUrl(resolution, params) {
-    const layers = this.params_.LAYERS;
+    if (this.url_ === undefined) {
-    const isSingleLayer = !Array.isArray(layers) || this.params_['LAYERS'].length === 1;
-    if (this.url_ === undefined || !isSingleLayer) {
       return undefined;
     }
 
@@ -213,10 +213,18 @@ class ImageWMS extends ImageSource {
       'SERVICE': 'WMS',
       'VERSION': DEFAULT_WMS_VERSION,
       'REQUEST': 'GetLegendGraphic',
-      'FORMAT': 'image/png',
+      'FORMAT': 'image/png'
-      'LAYER': layers
     };
 
+    if (params === undefined || params['LAYER'] === undefined) {
+      const layers = this.params_.LAYERS;
+      const isSingleLayer = !Array.isArray(layers) || layers.length === 1;
+      if (!isSingleLayer) {
+        return undefined;
+      }
+      baseParams['LAYER'] = layers;
+    }
+
     if (resolution !== undefined) {
       const mpu = this.getProjection() ? this.getProjection().getMetersPerUnit() : 1;
       const dpi = 25.4 / 0.28;

src/ol/source/TileWMS.js

@@ -219,15 +219,15 @@ class TileWMS extends TileImage {
    *
    * @param {number} [resolution] Resolution. If set to undefined, `SCALE`
    *     will not be calculated and included in URL.
-   * @param {Object} [params] GetLegendGraphic params. Default `FORMAT` is
+   * @param {Object} [params] GetLegendGraphic params. If `LAYER` is set, the
-   *     `image/png`. `VERSION` should not be specified here.
+   *     request is generated for this wms layer, else it will try to use the
+   *     configured wms layer. Default `FORMAT` is `image/png`.
+   *     `VERSION` should not be specified here.
    * @return {string|undefined} GetLegendGraphic URL.
    * @api
    */
   getLegendUrl(resolution, params) {
-    const layers = this.params_.LAYERS;
+    if (this.urls[0] === undefined) {
-    const isSingleLayer = !Array.isArray(layers) || this.params_['LAYERS'].length === 1;
-    if (this.urls[0] === undefined || !isSingleLayer) {
       return undefined;
     }
 
@@ -235,10 +235,18 @@ class TileWMS extends TileImage {
       'SERVICE': 'WMS',
       'VERSION': DEFAULT_WMS_VERSION,
       'REQUEST': 'GetLegendGraphic',
-      'FORMAT': 'image/png',
+      'FORMAT': 'image/png'
-      'LAYER': layers
     };
 
+    if (params === undefined || params['LAYER'] === undefined) {
+      const layers = this.params_.LAYERS;
+      const isSingleLayer = !Array.isArray(layers) || layers.length === 1;
+      if (!isSingleLayer) {
+        return undefined;
+      }
+      baseParams['LAYER'] = layers;
+    }
+
     if (resolution !== undefined) {
       const mpu = this.getProjection() ? this.getProjection().getMetersPerUnit() : 1;
       const dpi = 25.4 / 0.28;

test/spec/ol/source/imagewms.test.js

@@ -368,7 +368,8 @@ describe('ol.source.ImageWMS', function() {
         WIDTH: 'WIDTH_VALUE',
         HEIGHT: 'HEIGHT_VALUE',
         EXCEPTIONS: 'EXCEPTIONS_VALUE',
-        LANGUAGE: 'LANGUAGE_VALUE'
+        LANGUAGE: 'LANGUAGE_VALUE',
+        LAYER: 'LAYER_VALUE'
       });
       const uri = new URL(url);
       expect(uri.protocol).to.be('http:');
@@ -376,7 +377,7 @@ describe('ol.source.ImageWMS', function() {
       expect(uri.pathname).to.be('/wms');
       const queryData = uri.searchParams;
       expect(queryData.get('FORMAT')).to.be('FORMAT_VALUE');
-      expect(queryData.get('LAYER')).to.be('layer');
+      expect(queryData.get('LAYER')).to.be('LAYER_VALUE');
       expect(queryData.get('REQUEST')).to.be('GetLegendGraphic');
       expect(queryData.get('SERVICE')).to.be('WMS');
       expect(queryData.get('VERSION')).to.be('1.3.0');

test/spec/ol/source/tilewms.test.js

@@ -337,7 +337,8 @@ describe('ol.source.TileWMS', function() {
         WIDTH: 'WIDTH_VALUE',
         HEIGHT: 'HEIGHT_VALUE',
         EXCEPTIONS: 'EXCEPTIONS_VALUE',
-        LANGUAGE: 'LANGUAGE_VALUE'
+        LANGUAGE: 'LANGUAGE_VALUE',
+        LAYER: 'LAYER_VALUE'
       });
       const uri = new URL(url);
       expect(uri.protocol).to.be('http:');
@@ -345,7 +346,7 @@ describe('ol.source.TileWMS', function() {
       expect(uri.pathname).to.be('/wms');
       const queryData = uri.searchParams;
       expect(queryData.get('FORMAT')).to.be('FORMAT_VALUE');
-      expect(queryData.get('LAYER')).to.be('layer');
+      expect(queryData.get('LAYER')).to.be('LAYER_VALUE');
       expect(queryData.get('REQUEST')).to.be('GetLegendGraphic');
       expect(queryData.get('SERVICE')).to.be('WMS');
       expect(queryData.get('VERSION')).to.be('1.3.0');