Merge pull request #5216 from m-kuhn/vectorFileWriter

Make error message accessible for python in vector file writer

doc/api_break.dox

@@ -2550,6 +2550,8 @@ in code which previously passed a null pointer to QgsVectorFileWriter.
 - setSymbologyScaleDenominator() and symbologyScaleDenominator() were renamed to setSymbologyScale() and symbologyScale()
 for consistency with other parts of the QGIS API.
 - The addFeature which takes a renderer argument was renamed to addFeatureWithStyle.
+- static `writeAsVectorFormat` calls no longer take a errorMessage argument in
+  python and instead return a `(errorCode, errorMessage)` tuple.
 
 
 QgsWMSLegendNode        {#qgis_api_break_3_0_QgsWMSLegendNode}

python/core/qgsvectorfilewriter.sip

@@ -226,7 +226,7 @@ Constructor
         const QgsCoordinateReferenceSystem &destCRS = QgsCoordinateReferenceSystem(),
         const QString &driverName = "ESRI Shapefile",
         bool onlySelected = false,
-        QString *errorMessage = 0,
+        QString *errorMessage /Out/ = 0,
         const QStringList &datasourceOptions = QStringList(),
         const QStringList &layerOptions = QStringList(),
         bool skipAttributeCreation = false,
@@ -271,7 +271,7 @@ Constructor
         const QgsCoordinateTransform &ct,
         const QString &driverName = "ESRI Shapefile",
         bool onlySelected = false,
-        QString *errorMessage = 0,
+        QString *errorMessage /Out/ = 0,
         const QStringList &datasourceOptions = QStringList(),
         const QStringList &layerOptions = QStringList(),
         bool skipAttributeCreation = false,
@@ -431,7 +431,7 @@ Optional feedback object allowing cancelation of layer save
         const QString &fileName,
         const QgsVectorFileWriter::SaveVectorOptions &options,
         QString *newFilename = 0,
-        QString *errorMessage = 0 );
+        QString *errorMessage /Out/ = 0 );
 %Docstring
  Writes a layer out to a vector file.
  \param layer source layer to write

src/core/qgsvectorfilewriter.h

@@ -276,7 +276,7 @@ class CORE_EXPORT QgsVectorFileWriter : public QgsFeatureSink
         const QgsCoordinateReferenceSystem &destCRS = QgsCoordinateReferenceSystem(),
         const QString &driverName = "ESRI Shapefile",
         bool onlySelected = false,
-        QString *errorMessage = nullptr,
+        QString *errorMessage SIP_OUT = nullptr,
         const QStringList &datasourceOptions = QStringList(),
         const QStringList &layerOptions = QStringList(),
         bool skipAttributeCreation = false,
@@ -321,7 +321,7 @@ class CORE_EXPORT QgsVectorFileWriter : public QgsFeatureSink
         const QgsCoordinateTransform &ct,
         const QString &driverName = "ESRI Shapefile",
         bool onlySelected = false,
-        QString *errorMessage = nullptr,
+        QString *errorMessage SIP_OUT = nullptr,
         const QStringList &datasourceOptions = QStringList(),
         const QStringList &layerOptions = QStringList(),
         bool skipAttributeCreation = false,
@@ -423,7 +423,7 @@ class CORE_EXPORT QgsVectorFileWriter : public QgsFeatureSink
         const QString &fileName,
         const QgsVectorFileWriter::SaveVectorOptions &options,
         QString *newFilename = nullptr,
-        QString *errorMessage = nullptr );
+        QString *errorMessage SIP_OUT = nullptr );
 
     //! Create a new vector file writer
     QgsVectorFileWriter( const QString &vectorFileName,

tests/src/python/test_qgsvectorfilewriter.py

@@ -115,13 +115,13 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         dest_file_name = os.path.join(str(QDir.tempPath()), 'datetime.shp')
         crs = QgsCoordinateReferenceSystem()
         crs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
             crs,
             'ESRI Shapefile')
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -159,11 +159,11 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         options.filterExtent = QgsRectangle(-111, 26, -96, 38)
 
         dest_file_name = os.path.join(str(QDir.tempPath()), 'extent_no_transform.shp')
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             source_layer,
             dest_file_name,
             options)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -184,11 +184,11 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         options.ct = QgsCoordinateTransform(source_layer.crs(), QgsCoordinateReferenceSystem.fromEpsgId(3785))
 
         dest_file_name = os.path.join(str(QDir.tempPath()), 'extent_transform.shp')
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             source_layer,
             dest_file_name,
             options)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -220,13 +220,13 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         dest_file_name = os.path.join(str(QDir.tempPath()), 'datetime.tab')
         crs = QgsCoordinateReferenceSystem()
         crs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
             crs,
             'MapInfo File')
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -274,14 +274,14 @@ class TestQgsVectorFileWriter(unittest.TestCase):
             dest_file_name = os.path.join(str(QDir.tempPath()), 'point_{}.shp'.format(QgsWkbTypes.displayString(t)))
             crs = QgsCoordinateReferenceSystem()
             crs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-            write_result = QgsVectorFileWriter.writeAsVectorFormat(
+            write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
                 ml,
                 dest_file_name,
                 'utf-8',
                 crs,
                 'ESRI Shapefile',
                 overrideGeometryType=t)
-            self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+            self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
             # Open result and check
             created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -299,13 +299,13 @@ class TestQgsVectorFileWriter(unittest.TestCase):
                                           'point_{}_copy.shp'.format(QgsWkbTypes.displayString(t)))
             crs = QgsCoordinateReferenceSystem()
             crs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-            write_result = QgsVectorFileWriter.writeAsVectorFormat(
+            write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
                 created_layer,
                 dest_file_name,
                 'utf-8',
                 crs,
                 'ESRI Shapefile')
-            self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+            self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
             # Open result and check
             created_layer_from_shp = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -337,14 +337,14 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         dest_file_name = os.path.join(str(QDir.tempPath()), 'to_multi.shp')
         crs = QgsCoordinateReferenceSystem()
         crs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
             crs,
             'ESRI Shapefile',
             forceMulti=True)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -379,14 +379,14 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         dest_file_name = os.path.join(str(QDir.tempPath()), 'all_attributes.shp')
         crs = QgsCoordinateReferenceSystem()
         crs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
             crs,
             'ESRI Shapefile',
             attributes=[])
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -399,14 +399,14 @@ class TestQgsVectorFileWriter(unittest.TestCase):
 
         # now test writing out only a subset of attributes
         dest_file_name = os.path.join(str(QDir.tempPath()), 'subset_attributes.shp')
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
             crs,
             'ESRI Shapefile',
             attributes=[1, 3])
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -417,14 +417,14 @@ class TestQgsVectorFileWriter(unittest.TestCase):
 
         # finally test writing no attributes
         dest_file_name = os.path.join(str(QDir.tempPath()), 'no_attributes.shp')
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
             crs,
             'ESRI Shapefile',
             skipAttributeCreation=True)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -463,7 +463,7 @@ class TestQgsVectorFileWriter(unittest.TestCase):
 
         dest_file_name = os.path.join(str(QDir.tempPath()), 'value_converter.shp')
         converter = TestFieldValueConverter(ml)
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
@@ -471,7 +471,7 @@ class TestQgsVectorFileWriter(unittest.TestCase):
             'ESRI Shapefile',
             attributes=[0, 2],
             fieldValueConverter=converter)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -501,13 +501,13 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         dest_file_name = os.path.join(str(QDir.tempPath()), 'integer64.tab')
         crs = QgsCoordinateReferenceSystem()
         crs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             dest_file_name,
             'utf-8',
             crs,
             'MapInfo File')
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         # Open result and check
         created_layer = QgsVectorLayer('{}|layerid=0'.format(dest_file_name), 'test', 'ogr')
@@ -558,11 +558,11 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         options.driverName = 'GPKG'
         options.layerName = 'test'
         filename = '/vsimem/out.gpkg'
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             filename,
             options)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         ds = ogr.Open(filename, update=1)
         lyr = ds.GetLayerByName('test')
@@ -597,11 +597,11 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         options.layerName = 'test'
         options.actionOnExistingFile = QgsVectorFileWriter.CreateOrOverwriteLayer
         filename = '/vsimem/out.gpkg'
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             filename,
             options)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         ds = ogr.Open(filename)
         lyr = ds.GetLayerByName('test')
@@ -626,11 +626,11 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         options.driverName = 'GPKG'
         options.layerName = 'test'
         filename = '/vsimem/out.gpkg'
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             filename,
             options)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         ds = ogr.Open(filename)
         lyr = ds.GetLayerByName('test')
@@ -658,11 +658,11 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         options.layerName = 'test'
         options.actionOnExistingFile = QgsVectorFileWriter.AppendToLayerNoNewFields
         filename = '/vsimem/out.gpkg'
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             filename,
             options)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         ds = ogr.Open(filename)
         lyr = ds.GetLayerByName('test')
@@ -691,11 +691,11 @@ class TestQgsVectorFileWriter(unittest.TestCase):
         options.layerName = 'test'
         options.actionOnExistingFile = QgsVectorFileWriter.AppendToLayerAddFields
         filename = '/vsimem/out.gpkg'
-        write_result = QgsVectorFileWriter.writeAsVectorFormat(
+        write_result, error_message = QgsVectorFileWriter.writeAsVectorFormat(
             ml,
             filename,
             options)
-        self.assertEqual(write_result, QgsVectorFileWriter.NoError)
+        self.assertEqual(write_result, QgsVectorFileWriter.NoError, error_message)
 
         ds = ogr.Open(filename)
         lyr = ds.GetLayerByName('test')

tests/src/python/utilities.py

@@ -105,25 +105,23 @@ def writeShape(theMemoryLayer, theFileName):
     myFileName = os.path.join(str(QDir.tempPath()), theFileName)
     print(myFileName)
     # Explicitly giving all options, not really needed but nice for clarity
-    myErrorMessage = ''
     myOptions = []
     myLayerOptions = []
     mySelectedOnlyFlag = False
     mySkipAttributesFlag = False
     myGeoCrs = QgsCoordinateReferenceSystem()
     myGeoCrs.createFromId(4326, QgsCoordinateReferenceSystem.EpsgCrsId)
-    myResult = QgsVectorFileWriter.writeAsVectorFormat(
+    myResult, myErrorMessage = QgsVectorFileWriter.writeAsVectorFormat(
         theMemoryLayer,
         myFileName,
         'utf-8',
         myGeoCrs,
         'ESRI Shapefile',
         mySelectedOnlyFlag,
-        myErrorMessage,
         myOptions,
         myLayerOptions,
         mySkipAttributesFlag)
-    assert myResult == QgsVectorFileWriter.NoError
+    assert myResult == QgsVectorFileWriter.NoError, 'Writing shape failed, Error {} ({})'.format(myResult, myErrorMessage)
 
 
 def doubleNear(a, b, tol=0.0000000001):