Add utility QgsMapLayerUtils.updateLayerSourcePath for easy replacement

of file paths in the source of a file-based layer
qgis · Aug 6, 2021 · a31a674 · a31a674
1 parent baa9062
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diff --git a/python/core/auto_generated/qgsmaplayerutils.sip.in b/python/core/auto_generated/qgsmaplayerutils.sip.in
@@ -46,6 +46,17 @@ This method can be used to test whether a layer is associated with a file path.
 .. versionadded:: 3.22
 %End
 
+    static bool updateLayerSourcePath( QgsMapLayer *layer, const QString &newPath );
+%Docstring
+Updates a ``layer``'s data source, replacing its data source with a path refering to ``newPath``.
+
+Returns ``True`` if the layer was updated, or ``False`` if the layer was not updated (e.g. it
+uses a data provider which does not specify paths in a layer URI.
+
+.. versionadded:: 3.22
+%End
+
+
 };
 
 

diff --git a/src/core/qgsmaplayerutils.cpp b/src/core/qgsmaplayerutils.cpp
@@ -121,3 +121,18 @@ bool QgsMapLayerUtils::layerSourceMatchesPath( const QgsMapLayer *layer, const Q
   const QVariantMap parts = QgsProviderRegistry::instance()->decodeUri( layer->providerType(), layer->source() );
   return parts.value( QStringLiteral( "path" ) ).toString() == path;
 }
+
+bool QgsMapLayerUtils::updateLayerSourcePath( QgsMapLayer *layer, const QString &newPath )
+{
+  if ( !layer || newPath.isEmpty() )
+    return false;
+
+  QVariantMap parts = QgsProviderRegistry::instance()->decodeUri( layer->providerType(), layer->source() );
+  if ( !parts.contains( QStringLiteral( "path" ) ) )
+    return false;
+
+  parts.insert( QStringLiteral( "path" ), newPath );
+  const QString newUri = QgsProviderRegistry::instance()->encodeUri( layer->providerType(), parts );
+  layer->setDataSource( newUri, layer->name(), layer->providerType() );
+  return true;
+}
diff --git a/src/core/qgsmaplayerutils.h b/src/core/qgsmaplayerutils.h
@@ -60,6 +60,17 @@ class CORE_EXPORT QgsMapLayerUtils
      */
     static bool layerSourceMatchesPath( const QgsMapLayer *layer, const QString &path );
 
+    /**
+     * Updates a \a layer's data source, replacing its data source with a path refering to \a newPath.
+     *
+     * Returns TRUE if the layer was updated, or FALSE if the layer was not updated (e.g. it
+     * uses a data provider which does not specify paths in a layer URI.
+     *
+     * \since QGIS 3.22
+     */
+    static bool updateLayerSourcePath( QgsMapLayer *layer, const QString &newPath );
+
+
 };
 
 #endif // QGSMAPLAYERUTILS_H

diff --git a/tests/src/python/test_qgsmaplayerutils.py b/tests/src/python/test_qgsmaplayerutils.py
@@ -91,6 +91,38 @@ def test_layerSourceMatchesPath(self):
         self.assertFalse(QgsMapLayerUtils.layerSourceMatchesPath(rl, 'aaaaa'))
         self.assertTrue(QgsMapLayerUtils.layerSourceMatchesPath(rl, unitTestDataPath() + '/mixed_layers.gpkg'))
 
+    def test_updateLayerSourcePath(self):
+        """
+        Test QgsMapLayerUtils.updateLayerSourcePath()
+        """
+        self.assertFalse(QgsMapLayerUtils.updateLayerSourcePath(None, ''))
+        self.assertFalse(QgsMapLayerUtils.updateLayerSourcePath(None, 'aaaaa'))
+
+        # shapefile
+        layer1 = QgsVectorLayer(unitTestDataPath() + '/points.shp', 'l1')
+        self.assertTrue(QgsMapLayerUtils.updateLayerSourcePath(layer1, unitTestDataPath() + '/points22.shp'))
+        self.assertEqual(layer1.source(), unitTestDataPath() + '/points22.shp')
+
+        # geopackage with layers
+        layer1 = QgsVectorLayer(unitTestDataPath() + '/mixed_layers.gpkg|layername=lines', 'l1')
+        self.assertTrue(QgsMapLayerUtils.updateLayerSourcePath(layer1, unitTestDataPath() + '/mixed_layers22.gpkg'))
+        self.assertEqual(layer1.source(), unitTestDataPath() + '/mixed_layers22.gpkg|layername=lines')
+        layer2 = QgsVectorLayer(unitTestDataPath() + '/mixed_layers.gpkg|layername=points', 'l1')
+        self.assertTrue(QgsMapLayerUtils.updateLayerSourcePath(layer2, unitTestDataPath() + '/mixed_layers22.gpkg'))
+        self.assertEqual(layer2.source(), unitTestDataPath() + '/mixed_layers22.gpkg|layername=points')
+
+        # raster layer from gpkg
+        rl = QgsRasterLayer(f'GPKG:{unitTestDataPath()}/mixed_layers.gpkg:band1')
+        self.assertTrue(QgsMapLayerUtils.updateLayerSourcePath(rl, unitTestDataPath() + '/mixed_layers22.gpkg'))
+        self.assertEqual(rl.source(), f'GPKG:{unitTestDataPath()}/mixed_layers22.gpkg:band1')
+
+        # a layer from a provider which doesn't use file based paths
+        layer = QgsVectorLayer("Point?field=x:string", 'my layer', "memory")
+        old_source = layer.source()
+        self.assertTrue(layer.isValid())
+        self.assertFalse(QgsMapLayerUtils.updateLayerSourcePath(layer, unitTestDataPath() + '/mixed_layers22.gpkg'))
+        self.assertEqual(layer.source(), old_source)
+
 
 if __name__ == '__main__':
     unittest.main()