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[OGR] Use OGR_F_SetFieldNull() with GDAL >= 2.2 to avoid GeoJSON fields to be unset (fixes #16812)

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This commit is contained in:
Even Rouault 2017-07-08 14:01:10 +02:00
parent 40d833ff5f
commit 7d67b02ae4
3 changed files with 43 additions and 2 deletions
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12
src/core/qgsvectorfilewriter.cpp
View File

@ -1949,7 +1949,19 @@ OGRFeatureH QgsVectorFileWriter::createFeature( const 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 )
{

22
src/providers/ogr/qgsogrprovider.cpp
View File

@ -1289,7 +1289,18 @@ bool QgsOgrProvider::addFeaturePrivate( QgsFeature &f, Flags flags )
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
{
@ -1684,7 +1695,18 @@ 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
{

11
tests/src/python/test_qgsvectorfilewriter.py
View File

@ -703,10 +703,17 @@ class TestQgsVectorFileWriter(unittest.TestCase):
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)