Fix [Tests][Server] Add WMS GetPrint group

src/server/services/wms/qgswmsrendercontext.cpp

@@ -287,6 +287,19 @@ bool QgsWmsRenderContext::isValidLayer( const QString &nickname ) const
   return layer( nickname ) != nullptr;
 }
 
+QList<QgsMapLayer *> QgsWmsRenderContext::layersFromGroup( const QString &nickname ) const
+{
+  QList<QgsMapLayer *> layers;
+  if ( mLayerGroups.contains( nickname ) )
+  {
+    for ( QgsMapLayer *layer : mLayerGroups[nickname] )
+    {
+      layers.append( layer );
+    }
+  }
+  return layers;
+}
+
 bool QgsWmsRenderContext::isValidGroup( const QString &name ) const
 {
   return mLayerGroups.contains( name );

src/server/services/wms/qgswmsrendercontext.h

@@ -178,6 +178,12 @@ namespace QgsWms
        */
       bool isValidLayer( const QString &nickname ) const;
 
+      /**
+       * Returns the group's layers list corresponding to the nickname, or
+       * an empty list if not found.
+       */
+      QList<QgsMapLayer *> layersFromGroup( const QString &nickname ) const;
+
       /**
        * Returns true if \a name is a group.
        */

src/server/services/wms/qgswmsrenderer.cpp

@@ -611,15 +611,38 @@ namespace QgsWms
           QList<QgsMapLayer *> layerSet;
           for ( auto layer : cMapParams.mLayers )
           {
-            QgsMapLayer *mlayer = mContext.layer( layer.mNickname );
-
-            if ( ! mlayer )
+            if ( mContext.isValidGroup( layer.mNickname ) )
             {
-              continue;
-            }
+              QList<QgsMapLayer *> layersFromGroup;
 
-            setLayerStyle( mlayer, layer.mStyle );
-            layerSet << mlayer;
+              for ( QgsMapLayer *layer : mContext.layersFromGroup( layer.mNickname ) )
+              {
+
+                if ( ! layer )
+                {
+                  continue;
+                }
+
+                layersFromGroup.push_front( layer );
+              }
+
+              if ( !layersFromGroup.isEmpty() )
+              {
+                layerSet.append( layersFromGroup );
+              }
+            }
+            else
+            {
+              QgsMapLayer *mlayer = mContext.layer( layer.mNickname );
+
+              if ( ! mlayer )
+              {
+                continue;
+              }
+
+              setLayerStyle( mlayer, layer.mStyle );
+              layerSet << mlayer;
+            }
           }
 
           layerSet << externalLayers( cMapParams.mExternalLayers );

tests/src/python/test_qgsserver_wms_getprint.py

@@ -362,6 +362,7 @@ class TestQgsServerWMSGetPrint(QgsServerTestBase):
             "VERSION": "1.1.1",
             "REQUEST": "GetPrint",
             "TEMPLATE": "layoutA4",
+            "FORMAT": "png",
             "map0:EXTENT": "-33626185.498,-13032965.185,33978427.737,16020257.031",
             "map0:LAYERS": "Country_Diagrams,Country_Labels,Country",
             "CRS": "EPSG:3857"
@@ -375,12 +376,13 @@ class TestQgsServerWMSGetPrint(QgsServerTestBase):
             "VERSION": "1.1.1",
             "REQUEST": "GetPrint",
             "TEMPLATE": "layoutA4",
+            "FORMAT": "png",
             "map0:EXTENT": "-33626185.498,-13032965.185,33978427.737,16020257.031",
             "map0:LAYERS": "CountryGroup",
             "CRS": "EPSG:3857"
         }.items())])
 
-        r_group, _ = self._result(self._execute_request(qs))
+        r_group, h = self._result(self._execute_request(qs))
 
         """ Debug check:
         f = open('grouped.png', 'wb+')
@@ -393,6 +395,8 @@ class TestQgsServerWMSGetPrint(QgsServerTestBase):
 
         self.assertEqual(r_individual, r_group, 'Individual layers query and group layers query results should be identical')
 
+        self._img_diff_error(r_group, h, "WMS_GetPrint_Group")
+
     def test_wms_getprint_legend(self):
         qs = "?" + "&".join(["%s=%s" % i for i in list({
             "MAP": urllib.parse.quote(self.projectPath),