setting a field to a value via field calculator freezes qgis when "Automatic Creation of Transaction Group" is enabled

[faridcher]

How to Reproduce
Try to set the tsize field of labs layer to NULL via field calculator .

related:
https://issues.qgis.org/issues/11422
subdiv.zip

[gioman]

@faridcher cannot confirm on 3.10.10 on Ubuntu 20.04-

[faridcher]

upgraded to 3.10.10 and the problem persists. Please try with attached gpkg file in the original post. Try to set the tsize field of labs layer to NULL.

thanks

[elpaso]

No issues here on QGIS master/linux

[gioman]

upgraded to 3.10.10 and the problem persists. Please try with attached gpkg file in the original post. Try to set the tsize field of labs layer to NULL.

thanks

@faridcher try with a new QGIS profile.

[faridcher]

A new profile did not help. However, the problem relates to the qgis project file and it occurs when "Automatic Creation of Transaction Group" is enabled in the "Project Properties > Data Sources". Un-checking that option solves it.

[elpaso]

This is indeed a big bad voracious 🐛

[gioman]

This is indeed a big bad voracious bug

@elpaso
same origin as #39177 ?

[elpaso]

Definitely related.

[elpaso]

I now know the source of the bug but the fix isn't trivial.

[elpaso]

See also: #39244

[elpaso]

Reproducing test case:

    def testTransactionGroupIterator(self):
        """Test issue GH #39178: the bug is that this test hangs
        forever in an endless loop"""

        project = QgsProject()
        project.setAutoTransaction(True)
        tmpfile = os.path.join(
            self.basetestpath, 'tempGeoPackageTransactionGroupIterator.gpkg')
        ds = ogr.GetDriverByName('GPKG').CreateDataSource(tmpfile)
        lyr = ds.CreateLayer('test', geom_type=ogr.wkbPoint)
        lyr.CreateField(ogr.FieldDefn('str_field', ogr.OFTString))

        f = ogr.Feature(lyr.GetLayerDefn())
        f.SetGeometry(ogr.CreateGeometryFromWkt('POINT (1 1)'))
        f.SetField('str_field', 'one')
        lyr.CreateFeature(f)

        del lyr
        del ds

        vl = QgsVectorLayer(tmpfile + '|layername=test', 'test', 'ogr')
        project.addMapLayers([vl])

        self.assertTrue(vl.startEditing())

        for f in vl.getFeatures():
            self.assertTrue(vl.changeAttributeValue(1, 1, 'new value'))

        # Test that QGIS sees the new changes
        self.assertEqual(next(vl.getFeatures()).attribute(1), 'new value')