Fix virtual layers using joined fields

Fix #46834
qgis · Jan 24, 2022 · 4fd2f04 · 4fd2f04
1 parent 5cdd5b5
commit 4fd2f04
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diff --git a/src/core/project/qgsproject.cpp b/src/core/project/qgsproject.cpp
@@ -39,6 +39,7 @@
 #include "qgsrelationmanager.h"
 #include "qgsannotationmanager.h"
 #include "qgsvectorlayerjoininfo.h"
+#include "qgsvectorlayerjoinbuffer.h"
 #include "qgsmapthemecollection.h"
 #include "qgslayerdefinition.h"
 #include "qgsunittypes.h"
@@ -1264,6 +1265,14 @@ bool QgsProject::addLayer( const QDomElement &layerElem, QList<QDomNode> &broken
   {
     emit readMapLayer( mapLayer.get(), layerElem );
     addMapLayers( newLayers );
+    // Try to resolve references here (this is necessary to set up joined fields that will be possibly used by
+    // virtual layers that point to this layer's joined field in their query otherwise they won't be valid ),
+    // a second attempt to resolve references will be done after all layers are loaded
+    // see https://github.com/qgis/QGIS/issues/46834
+    if ( QgsVectorLayer *vLayer = qobject_cast<QgsVectorLayer *>( mapLayer.get() ) )
+    {
+      vLayer->joinBuffer()->resolveReferences( this );
+    }
   }
   else
   {

diff --git a/tests/src/python/test_provider_virtual.py b/tests/src/python/test_provider_virtual.py
@@ -1366,6 +1366,45 @@ def test_layer_starting_with_digit(self):
         vl = QgsVectorLayer(df.toString(), "1_layer_virtual", "virtual")
         self.assertTrue(vl.isValid())
 
+    def test_layer_using_joined_fields_from_another_layer(self):
+        """Test issue GH #46834"""
+
+        project = QgsProject.instance()
+        project.clear()
+        layer_1 = QgsVectorLayer('Point?crs=epsg:4326&field=fid:integer', 'layer_1', 'memory')
+        layer_2 = QgsVectorLayer('Point?crs=epsg:4326&field=fid:integer', 'layer_2', 'memory')
+
+        project.addMapLayers([layer_1])
+
+        # Add a join from 2 to 1
+        join_info = QgsVectorLayerJoinInfo()
+        join_info.setJoinLayer(layer_1)
+        join_info.setJoinFieldName('layer_1_fid')
+        join_info.setTargetFieldName('fid')
+        self.assertTrue(layer_2.addJoin(join_info))
+        self.assertIn('layer_1_fid', layer_2.fields().names())
+
+        project.addMapLayers([layer_2])
+
+        df = QgsVirtualLayerDefinition()
+        df.setQuery('select fid, layer_1_fid from "layer_2"')
+        vl = QgsVectorLayer(df.toString(), "virtual", "virtual")
+        self.assertTrue(vl.isValid())
+
+        project.addMapLayers([vl])
+
+        tmp = QTemporaryDir()
+        path = tmp.path()
+        project.write(os.path.join(path, 'test_4683.qgs'))
+
+        project.clear()
+        project.read(os.path.join(path, 'test_4683.qgs'))
+
+        layer_2 = project.mapLayersByName('layer_2')[0]
+        vl = project.mapLayersByName('virtual')[0]
+
+        self.assertTrue(vl.isValid())
+
 
 if __name__ == '__main__':
     unittest.main()