QGIS » QGIS Application

Hello, I have the very same problem porting my plugin.

Maybe the following helps somehow (not sure if is it appropriate to post here):

from qgis.PyQt.QtSql import QSqlDatabase, QSqlQuery

db = QSqlDatabase.addDatabase('QSPATIALITE')
db.setDatabaseName("Path to Spatialite File e.g. manually created with QGIS")
print(db.isValid(), QSqlDatabase.isDriverAvailable('QSPATIALITE')) #returns both True, if query below is commented out

if not db.open():
    print("DB not open")
else:
    print("DB open")
    q = QSqlQuery(db)
    q.exec_("SELECT sqlite_version(), spatialite_version()")
    q.first()
    print(str(q.value(0)), str(q.value(1)))
    db.close()

Running this code in the QGIS python console (3.0.2) results in a crash (it works in 2.18.19):

QSqlCachedResult::detachFromResultSet :
QSqlQuery::~QSqlQuery :
PyInit_sip :
Py_HashPointer :
Py_CheckFunctionResult :
PyEval_EvalFrameDefault :
PyErr_Occurred :
PyEval_EvalCode
... much more here ...

QGIS Info
QGIS Version: 3.0.2-Girona
QGIS code revision: 307d082e3d
Compiled against Qt: 5.9.2
Running against Qt: 5.9.2
Compiled against GDAL: 2.2.4
Running against GDAL: 2.2.4

System Info
CPU Type: x86_64
Kernel Type: winnt
Kernel Version: 10.0.16299

I am thinking about a work around using qgis.utils.spatialite_connect for all spatial queries (https://gis.stackexchange.com/questions/260527/how-to-create-a-spatialite-layer-in-qgis-3-with-python) and the 'QSQLITE' driver for non spatial queries to populate PyQt Views/Models/DataMappers (which in my case do not require spatial queries)

I've done with same workaround as you thinking - works for now.

db = QSqlDatabase.addDatabase('QSQLITE')
query = QSqlQuery(db)
request = query.exec_(exp)
if request:
    [...]
else:
    connection = spatialite_connect(dbfile)
    cursor = connection.cursor()
    [...]

This problem appears to be fixed #19419
Just successfully tried the code I posted above with QGIS version: 3.2.2-Bonn, QGIS code revision: 26842169e9

Yes, I can confirm, works now! Tested on nightly 3.3.0 rev 85d740026a