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[OGR] Use OGR_F_SetFieldNull() with GDAL >= 2.2 to avoid GeoJSON fiel…
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…ds to be unset (fixes #16812)
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rouault committed Jul 8, 2017
1 parent f6de1d4 commit fda97b2
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Showing 3 changed files with 43 additions and 2 deletions.
12 changes: 12 additions & 0 deletions src/core/qgsvectorfilewriter.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1976,7 +1976,19 @@ OGRFeatureH QgsVectorFileWriter::createFeature( QgsFeature& feature )
QVariant attrValue = feature.attribute( fldIdx );

if ( !attrValue.isValid() || attrValue.isNull() )
{
// Starting with GDAL 2.2, there are 2 concepts: unset fields and null fields
// whereas previously there was only unset fields. For a GeoJSON output,
// leaving a field unset will cause it to not appear at all in the output
// feature.
// When all features of a layer have a field unset, this would cause the
// field to not be present at all in the output, and thus on reading to
// have disappeared. #16812
#ifdef OGRNullMarker
OGR_F_SetFieldNull( poFeature, ogrField );
#endif
continue;
}

if ( mFieldValueConverter )
{
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22 changes: 22 additions & 0 deletions src/providers/ogr/qgsogrprovider.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1272,7 +1272,18 @@ bool QgsOgrProvider::addFeature( QgsFeature& f )
QVariant attrVal = attrs.at( qgisAttId );
if ( attrVal.isNull() || ( type != OFTString && attrVal.toString().isEmpty() ) )
{
// Starting with GDAL 2.2, there are 2 concepts: unset fields and null fields
// whereas previously there was only unset fields. For a GeoJSON output,
// leaving a field unset will cause it to not appear at all in the output
// feature.
// When all features of a layer have a field unset, this would cause the
// field to not be present at all in the output, and thus on reading to
// have disappeared. #16812
#ifdef OGRNullMarker
OGR_F_SetFieldNull( feature, ogrAttId );
#else
OGR_F_UnsetField( feature, ogrAttId );
#endif
}
else
{
Expand Down Expand Up @@ -1683,7 +1694,18 @@ bool QgsOgrProvider::changeAttributeValues( const QgsChangedAttributesMap &attr_

if ( it2->isNull() || ( type != OFTString && it2->toString().isEmpty() ) )
{
// Starting with GDAL 2.2, there are 2 concepts: unset fields and null fields
// whereas previously there was only unset fields. For a GeoJSON output,
// leaving a field unset will cause it to not appear at all in the output
// feature.
// When all features of a layer have a field unset, this would cause the
// field to not be present at all in the output, and thus on reading to
// have disappeared. #16812
#ifdef OGRNullMarker
OGR_F_SetFieldNull( of, f );
#else
OGR_F_UnsetField( of, f );
#endif
}
else
{
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11 changes: 9 additions & 2 deletions tests/src/python/test_qgsvectorfilewriter.py
Original file line number Diff line number Diff line change
Expand Up @@ -675,10 +675,17 @@ def testOverwriteLayer(self):
self.assertIsNotNone(lyr)
f = lyr.GetNextFeature()
self.assertEqual(f['firstfield'], 3)
self.assertFalse(f.IsFieldSet('secondfield'))
if hasattr(f, "IsFieldSetAndNotNull"):
# GDAL >= 2.2
self.assertFalse(f.IsFieldSetAndNotNull('secondfield'))
else:
self.assertFalse(f.IsFieldSet('secondfield'))
f = lyr.GetNextFeature()
self.assertEqual(f['firstfield'], 4)
self.assertFalse(f.IsFieldSet('secondfield'))
if hasattr(f, "IsFieldSetAndNotNull"):
self.assertFalse(f.IsFieldSetAndNotNull('secondfield'))
else:
self.assertFalse(f.IsFieldSet('secondfield'))
f = lyr.GetNextFeature()
self.assertEqual(f['firstfield'], 5)
self.assertEqual(f['secondfield'], -1)
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