Add api to determine attribute capabilities for QgsVectorLayerExporter

nyalldawson · nyalldawson · commit b28bf203726f · 2023-04-22T09:18:06.000+10:00
diff --git a/python/core/auto_generated/vector/qgsvectorlayerexporter.sip.in b/python/core/auto_generated/vector/qgsvectorlayerexporter.sip.in
@@ -103,6 +103,13 @@ Returns the number of error messages encountered during the export.
 .. seealso:: :py:func:`errorMessage`
 
 .. seealso:: :py:func:`errorCode`
+%End
+
+    Qgis::VectorDataProviderAttributeEditCapabilities attributeEditCapabilities() const;
+%Docstring
+Returns the attribute capabilities of the exporter.
+
+.. versionadded:: 3.32
 %End
 
     virtual bool addFeatures( QgsFeatureList &features, QgsFeatureSink::Flags flags = QgsFeatureSink::Flags() );
diff --git a/src/core/qgis.h b/src/core/qgis.h
@@ -654,6 +654,24 @@ class CORE_EXPORT Qgis
     };
     Q_ENUM( VectorExportResult )
 
+    /**
+     * Capabilities supported by a QgsVectorFileWriter object.
+     * \since QGIS 3.32
+     */
+    enum class VectorFileWriterCapability : int
+    {
+      FieldAliases = 1 << 0, //!< Writer can support field aliases
+      FieldComments = 1 << 2, //!< Writer can support field comments
+    };
+    Q_ENUM( VectorFileWriterCapability )
+
+    /**
+     * Capabilities supported by a QgsVectorFileWriter object.
+     * \since QGIS 3.32
+     */
+    Q_DECLARE_FLAGS( VectorFileWriterCapabilities, VectorFileWriterCapability )
+    Q_FLAG( VectorFileWriterCapabilities )
+
     /**
      * SqlLayerDefinitionCapability enum lists the arguments supported by the provider when creating SQL query layers.
      * \since QGIS 3.22
@@ -3554,6 +3572,7 @@ Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::LayerTreeFilterFlags )
 Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::LabelLinePlacementFlags )
 Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::LabelPolygonPlacementFlags )
 Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::DatabaseProviderConnectionCapabilities2 )
+Q_DECLARE_OPERATORS_FOR_FLAGS( Qgis::VectorFileWriterCapabilities )
 
 // hack to workaround warnings when casting void pointers
 // retrieved from QLibrary::resolve to function pointers.
diff --git a/src/core/vector/qgsvectorlayerexporter.cpp b/src/core/vector/qgsvectorlayerexporter.cpp
@@ -200,6 +200,11 @@ QString QgsVectorLayerExporter::errorMessage() const
   return mErrorMessage;
 }
 
+Qgis::VectorDataProviderAttributeEditCapabilities QgsVectorLayerExporter::attributeEditCapabilities() const
+{
+  return mProvider ? mProvider->attributeEditCapabilities() : Qgis::VectorDataProviderAttributeEditCapabilities();
+}
+
 bool QgsVectorLayerExporter::addFeatures( QgsFeatureList &features, Flags flags )
 {
   QgsFeatureList::iterator fIt = features.begin();
diff --git a/src/core/vector/qgsvectorlayerexporter.h b/src/core/vector/qgsvectorlayerexporter.h
@@ -120,6 +120,13 @@ class CORE_EXPORT QgsVectorLayerExporter : public QgsFeatureSink
      */
     int errorCount() const { return mErrorCount; }
 
+    /**
+     * Returns the attribute capabilities of the exporter.
+     *
+     * \since QGIS 3.32
+     */
+    Qgis::VectorDataProviderAttributeEditCapabilities attributeEditCapabilities() const;
+
     bool addFeatures( QgsFeatureList &features, QgsFeatureSink::Flags flags = QgsFeatureSink::Flags() ) override;
     bool addFeature( QgsFeature &feature, QgsFeatureSink::Flags flags = QgsFeatureSink::Flags() ) override;
     QString lastError() const override;
diff --git a/tests/src/python/test_provider_ogr.py b/tests/src/python/test_provider_ogr.py
@@ -3396,6 +3396,40 @@ def testFieldComment(self):
             self.assertEqual(fields[2].name(), 'field2')
             self.assertEqual(fields[2].comment(), '')
 
+    @unittest.skipIf(int(gdal.VersionInfo('VERSION_NUM')) < GDAL_COMPUTE_VERSION(3, 7, 0), "GDAL 3.7 required")
+    def test_exporter_capabilities(self):
+        with tempfile.TemporaryDirectory() as temp_dir:
+            dest_file_name = os.path.join(temp_dir,
+                                          'test_gpkg.gpkg')
+
+            layer = QgsVectorLayer("point?crs=epsg:4326&field=id:integer",
+                                   "Scratch point layer", "memory")
+
+            exporter = QgsVectorLayerExporter(dest_file_name,
+                                              'ogr',
+                                              layer.fields(),
+                                              layer.wkbType(),
+                                              layer.crs())
+
+            self.assertTrue(
+                exporter.attributeEditCapabilities() & Qgis.VectorDataProviderAttributeEditCapability.EditAlias)
+            self.assertTrue(
+                exporter.attributeEditCapabilities() & Qgis.VectorDataProviderAttributeEditCapability.EditComment)
+
+            dest_file_name = os.path.join(temp_dir,
+                                          'test_shp.shp')
+
+            exporter = QgsVectorLayerExporter(dest_file_name,
+                                              'ogr',
+                                              layer.fields(),
+                                              layer.wkbType(),
+                                              layer.crs())
+
+            self.assertFalse(
+                exporter.attributeEditCapabilities() & Qgis.VectorDataProviderAttributeEditCapability.EditAlias)
+            self.assertFalse(
+                exporter.attributeEditCapabilities() & Qgis.VectorDataProviderAttributeEditCapability.EditComment)
+
 
 if __name__ == '__main__':
     unittest.main()

Original file line number	Diff line number	Diff line change
`@@ -200,6 +200,11 @@ QString QgsVectorLayerExporter::errorMessage() const`
`200`	`200`	`return mErrorMessage;`
`201`	`201`	`}`
`202`	`202`
	`203`	`+Qgis::VectorDataProviderAttributeEditCapabilities QgsVectorLayerExporter::attributeEditCapabilities() const`
	`204`	`+{`
	`205`	`+ return mProvider ? mProvider->attributeEditCapabilities() : Qgis::VectorDataProviderAttributeEditCapabilities();`
	`206`	`+}`
	`207`	`+`
`203`	`208`	`bool QgsVectorLayerExporter::addFeatures( QgsFeatureList &features, Flags flags )`
`204`	`209`	`{`
`205`	`210`	`QgsFeatureList::iterator fIt = features.begin();`