qgsvectorlayer: Properly invalidate extent cache on feature deletion

This change is similar to the previous commit on feature addition.

When a feature is removed from a `QgsVectorLayer`
`QgsVectorLayer::deleteFeature` is called. This function makes mostly
2 things in case of a successful operation:
1. it calls `QgsVectorLayerEditBuffer::deleteFeature` which itself
   will emit the `QgsVectorLayerEditBuffer::featureDeleted`
   signal. Finally, `QgsVectorLayer` listend to this signal to
   directly emit the `QgsVectorLayer::featureDeleted` signal
2. Call `QgsVectorLayer::updateExtents()` to invalidate the cache of
   the extent

In practice, this means that the `QgsVectorLayer::featureDeleted`
signal may be emitted before the cache of the extent is
invalidated. This can cause some issues.

This issue is solved by calling `updateExtents()` before emitting the
`featureDeleted` signal.

src/core/vector/qgsvectorlayer.cpp

@@ -3817,14 +3817,7 @@ bool QgsVectorLayer::deleteFeature( QgsFeatureId fid, QgsVectorLayer::DeleteCont
   if ( !mEditBuffer )
     return false;
 
-  bool res = deleteFeatureCascade( fid, context );
-
-  if ( res )
-  {
-    updateExtents();
-  }
-
-  return res;
+  return deleteFeatureCascade( fid, context );
 }
 
 bool QgsVectorLayer::deleteFeatures( const QgsFeatureIds &fids, QgsVectorLayer::DeleteContext *context )
@@ -5973,6 +5966,8 @@ void QgsVectorLayer::onFeatureDeleted( QgsFeatureId fid )
 {
   QGIS_PROTECT_QOBJECT_THREAD_ACCESS
 
+  updateExtents();
+
   if ( mEditCommandActive  || mCommitChangesActive )
   {
     mDeletedFids << fid;

tests/src/core/testqgsvectorlayer.cpp

@@ -504,6 +504,7 @@ void TestQgsVectorLayer::testAddFeatureExtentUpdated()
   QCOMPARE( layerLine->extent(), QgsRectangle() );
 
   const QSignalSpy spyAdded( layerLine, &QgsVectorLayer::featureAdded );
+  const QSignalSpy spyDeleted( layerLine, &QgsVectorLayer::featureDeleted );
 
   QgsFeature lineF1;
   lineF1.setGeometry( QgsGeometry::fromWkt( QStringLiteral( "LineString (2 1, 1 1, 1 5, 7 12)" ) ) );
@@ -514,12 +515,27 @@ void TestQgsVectorLayer::testAddFeatureExtentUpdated()
     QCOMPARE( layerLine->extent3D(), QgsBox3D( 1, 1, std::numeric_limits<double>::quiet_NaN(), 7, 12, std::numeric_limits<double>::quiet_NaN() ) );
   } );
 
+  connect( layerLine, &QgsVectorLayer::featureDeleted, this, [&layerLine, &lineF1]( const QgsFeatureId &fid ) {
+    QCOMPARE( fid, lineF1.id() );
+    QCOMPARE( layerLine->extent(), QgsRectangle() );
+    QCOMPARE( layerLine->extent3D(), QgsBox3D() );
+  }
+
+  );
+
   layerLine->startEditing();
   layerLine->addFeature( lineF1 );
   QCOMPARE( spyAdded.count(), 1 );
+  QCOMPARE( spyDeleted.count(), 0 );
   QCOMPARE( layerLine->featureCount(), static_cast<long>( 1 ) );
   QCOMPARE( spyAdded.at( 0 ).at( 0 ), QVariant( lineF1.id() ) );
 
+  layerLine->deleteFeature( lineF1.id() );
+  QCOMPARE( spyAdded.count(), 1 );
+  QCOMPARE( spyDeleted.count(), 1 );
+  QCOMPARE( layerLine->featureCount(), static_cast<long>( 0 ) );
+  QCOMPARE( spyDeleted.at( 0 ).at( 0 ), QVariant( lineF1.id() ) );
+
   delete layerLine;
 }
 

tests/src/python/test_qgsvectorlayer.py

@@ -701,6 +701,7 @@ def test_AddFeature(self):
 
         def checkAfter():
             self.assertEqual(layer.featureCount(), 1)
+            self.assertEqual(layer.extent(), QgsRectangle(1, 2, 1, 2))
 
             # check select+nextFeature
             f = next(layer.getFeatures())
@@ -712,6 +713,7 @@ def checkAfter():
 
         def checkBefore():
             self.assertEqual(layer.featureCount(), 0)
+            self.assertEqual(layer.extent(), QgsRectangle())
 
             # check select+nextFeature
             with self.assertRaises(StopIteration):
@@ -721,10 +723,15 @@ def checkBefore():
 
         spy = QSignalSpy(layer.layerModified)
         repaint_spy = QSignalSpy(layer.repaintRequested)
+        feature_added_spy = QSignalSpy(layer.featureAdded)
+        feature_deleted_spy = QSignalSpy(layer.featureDeleted)
 
         # try to add feature without editing mode
         self.assertFalse(layer.addFeature(feat))
         self.assertEqual(len(repaint_spy), 0)
+        self.assertEqual(len(feature_added_spy), 0)
+        self.assertEqual(len(feature_deleted_spy), 0)
+        self.assertEqual(layer.extent(), QgsRectangle())
 
         # add feature
         layer.startEditing()
@@ -733,6 +740,9 @@ def checkBefore():
         bad_feature = QgsFeature()
         self.assertFalse(layer.addFeature(bad_feature))
         self.assertEqual(len(repaint_spy), 0)
+        self.assertEqual(len(feature_added_spy), 0)
+        self.assertEqual(len(feature_deleted_spy), 0)
+        self.assertEqual(layer.extent(), QgsRectangle())
 
         self.assertEqual(len(spy), 0)
 
@@ -741,12 +751,16 @@ def checkBefore():
 
         self.assertEqual(len(spy), 1)
         self.assertEqual(len(repaint_spy), 1)
+        self.assertEqual(len(feature_added_spy), 1)
+        self.assertEqual(len(feature_deleted_spy), 0)
 
         checkAfter()
         self.assertEqual(layer.dataProvider().featureCount(), 0)
 
         # now try undo/redo
         layer.undoStack().undo()
+        self.assertEqual(len(feature_added_spy), 1)
+        self.assertEqual(len(feature_deleted_spy), 1)
         checkBefore()
         self.assertEqual(len(spy), 2)
         self.assertEqual(len(repaint_spy), 2)
@@ -756,6 +770,8 @@ def checkBefore():
 
         self.assertEqual(len(spy), 3)
         self.assertEqual(len(repaint_spy), 3)
+        self.assertEqual(len(feature_added_spy), 2)
+        self.assertEqual(len(feature_deleted_spy), 1)
 
         self.assertTrue(layer.commitChanges())