Add support for setting field comments to OGR provider connection

nyalldawson · nyalldawson · commit a1345f04c704 · 2023-04-18T16:04:13.000+10:00
diff --git a/src/core/providers/ogr/qgsogrproviderconnection.cpp b/src/core/providers/ogr/qgsogrproviderconnection.cpp
@@ -453,6 +453,10 @@ void QgsOgrProviderConnection::setDefaultCapabilities()
     {
       mCapabilities2 |= Qgis::DatabaseProviderConnectionCapability2::SetFieldAlias;
     }
+    if ( CSLFindString( papszTokens, "Comment" ) >= 0 )
+    {
+      mCapabilities2 |= Qgis::DatabaseProviderConnectionCapability2::SetFieldComment;
+    }
 #endif
 
     CSLDestroy( papszTokens );
@@ -1061,6 +1065,46 @@ void QgsOgrProviderConnection::setFieldAlias( const QString &fieldName, const QS
 #endif
 }
 
+void QgsOgrProviderConnection::setFieldComment( const QString &fieldName, const QString &schema, const QString &tableName, const QString &comment ) const
+{
+#if GDAL_VERSION_NUM >= GDAL_COMPUTE_VERSION(3,7,0)
+  if ( ! schema.isEmpty() )
+  {
+    QgsMessageLog::logMessage( QStringLiteral( "Schema is not supported by OGR, ignoring" ), QStringLiteral( "OGR" ), Qgis::MessageLevel::Info );
+  }
+
+  QString errCause;
+  QgsOgrLayerUniquePtr layer = QgsOgrProviderUtils::getLayer( uri(),
+                               true,
+                               QStringList(),
+                               tableName, errCause, true );
+  if ( !layer )
+  {
+    throw QgsProviderConnectionException( QObject::tr( "There was an error opening the dataset: %1" ).arg( errCause ) );
+  }
+
+  //type does not matter, it will not be used
+  gdal::ogr_field_def_unique_ptr fld( OGR_Fld_Create( fieldName.toUtf8().constData(), OFTReal ) );
+  OGR_Fld_SetComment( fld.get(), comment.toUtf8().constData() );
+
+  const int fieldIndex = layer->GetLayerDefn().GetFieldIndex( fieldName.toUtf8().constData() );
+  if ( fieldIndex < 0 )
+  {
+    throw QgsProviderConnectionException( QObject::tr( "Could not set comment for %1 - field does not exist" ).arg( fieldName ) );
+  }
+  if ( layer->AlterFieldDefn( fieldIndex, fld.get(), ALTER_COMMENT_FLAG ) != OGRERR_NONE )
+  {
+    throw QgsProviderConnectionException( QObject::tr( "Could not set comment: %1" ).arg( CPLGetLastErrorMsg() ) );
+  }
+#else
+  ( void )fieldName;
+  ( void )schema;
+  ( void )tableName;
+  ( void )comment;
+  throw QgsProviderConnectionException( QObject::tr( "Setting field comments for datasets requires GDAL 3.7 or later" ) );
+#endif
+}
+
 QgsAbstractDatabaseProviderConnection::SqlVectorLayerOptions QgsOgrProviderConnection::sqlOptions( const QString &layerSource )
 {
   SqlVectorLayerOptions options;
diff --git a/src/core/providers/ogr/qgsogrproviderconnection.h b/src/core/providers/ogr/qgsogrproviderconnection.h
@@ -90,6 +90,7 @@ class QgsOgrProviderConnection : public QgsAbstractDatabaseProviderConnection
     void addFieldDomain( const QgsFieldDomain &domain, const QString &schema ) const override;
     void renameField( const QString &schema, const QString &tableName, const QString &name, const QString &newName ) const override;
     void setFieldAlias( const QString &fieldName, const QString &schema, const QString &tableName, const QString &alias ) const override;
+    void setFieldComment( const QString &fieldName, const QString &schema, const QString &tableName, const QString &comment ) const override;
     SqlVectorLayerOptions sqlOptions( const QString &layerSource ) override;
     QList< Qgis::RelationshipCardinality > supportedRelationshipCardinalities() const override;
     QList< Qgis::RelationshipStrength > supportedRelationshipStrengths() const override;
diff --git a/tests/src/python/test_provider_ogr.py b/tests/src/python/test_provider_ogr.py
@@ -3225,6 +3225,46 @@ def test_provider_connection_set_field_alias(self):
             fields = layer.fields()
             self.assertEqual(fields['my_field'].alias(), 'my alias')
 
+    @unittest.skipIf(int(gdal.VersionInfo('VERSION_NUM')) < GDAL_COMPUTE_VERSION(3, 7, 0), "GDAL 3.7 required")
+    def test_provider_connection_set_field_comment(self):
+        """
+        Test setting field comments via the connections api
+        """
+        metadata = QgsProviderRegistry.instance().providerMetadata('ogr')
+        with tempfile.TemporaryDirectory() as temp_dir:
+            tmpfile = os.path.join(temp_dir, 'test_gpkg.gpkg')
+
+            ok, err = metadata.createDatabase(tmpfile)
+            self.assertTrue(ok)
+            self.assertFalse(err)
+
+            conn = metadata.createConnection(tmpfile, {})
+            self.assertTrue(conn)
+
+            fields = QgsFields()
+            field = QgsField('my_field', QVariant.String)
+            fields.append(field)
+            conn.createVectorTable('', 'test', fields, QgsWkbTypes.Point, QgsCoordinateReferenceSystem('EPSG:4326'), False, {})
+            layer = QgsVectorLayer(tmpfile + '|layername=test')
+            self.assertTrue(layer.isValid())
+
+            del layer
+
+            self.assertTrue(
+                conn.capabilities2() & Qgis.DatabaseProviderConnectionCapability2.SetFieldComment)
+
+            # field does not exist
+            with self.assertRaises(QgsProviderConnectionException):
+                conn.setFieldComment('not field', '', 'test', 'my comment')
+
+            conn.setFieldComment('my_field', '', 'test', 'my comment')
+
+            layer = QgsVectorLayer(tmpfile + '|layername=test')
+            self.assertTrue(layer.isValid())
+
+            fields = layer.fields()
+            self.assertEqual(fields['my_field'].comment(), 'my comment')
+
     @unittest.skipIf(int(gdal.VersionInfo('VERSION_NUM')) < GDAL_COMPUTE_VERSION(3, 7, 0), "GDAL 3.7 required")
     def test_provider_set_field_alias(self):
         """
