[QGIS-Developer] pyqgis getFeatures(<FilterExpression>) doesn't always fetch modified geometry

[Matthias Kuhn]

Hi

I could replicate it here and can confirm it is a bug and commitChanges() a
functional band aid for scripts.

Can you open an issue on github including this testcase?

Thanks
Matthias

On Sun, Dec 12, 2021 at 8:07 AM Ujaval Gandhi <ujaval at spatialthoughts.com>
wrote:

> Try calling layer.commitChanges() after changing the geometry.
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> Ujaval Gandhi
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>
> On Sat, Dec 11, 2021 at 6:55 PM Erik Polzin <eriktpol at gmail.com> wrote:
>
>> Hi all,
>>
>> Noticed some strange behaviour in QGIS' Python API the other day.
>> I needed to get a subset of points from a memory layer of point features,
>> and had previously done so by calling getFeatures(), and then filtering
>> this iterable in Python. I thought I could speed it up by using a filter
>> expression directly to let c++ do the filtering instead, but was surprised
>> to see that now the geometry wasn't up to date with the memory layer's edit
>> buffer.
>>
>> I've replicated the behaviour it in a small script here:
>>
>> from qgis.core import QgsVectorLayer, QgsField, QgsGeometry, QgsPointXY,
>> QgsFeature
>> from PyQt5.QtCore import QVariant
>>
>> layer = QgsVectorLayer("Point", "test", "memory")
>> pr = layer.dataProvider()
>> pr.addAttributes([QgsField("name", QVariant.String)])
>> layer.updateFields()
>>
>> initialGeom = QgsGeometry.fromPointXY(QgsPointXY(0, 0))
>> f = QgsFeature()
>> f.setGeometry(initialGeom)
>> f.setAttributes(["Tom"])
>> added, (f,) = layer.dataProvider().addFeatures([f])
>>
>> layer.startEditing()
>> editedGeom = QgsGeometry.fromPointXY(QgsPointXY(1, 1))
>> layer.changeGeometry(f.id(), editedGeom)
>> layer.changeAttributeValues(f.id(), {0: "Harry"})
>>
>> for f in layer.getFeatures():
>>     print(f.id(), f.attributes(), f.geometry())
>>
>> for f in layer.getFeatures("name = 'Harry'"):
>>     print(f.id(), f.attributes(), f.geometry())
>>
>> # >>> Prints different results!
>>
>> This only seems to happen with both calls to changeGeometry and
>> changeAttributeValues.
>> Is there some way of getting around this? Would it be classified as a bug
>> in the API?
>>
>> Cheers,
>> Erik
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