ogr2ogr GML->GPKG conversion via VRT - attribute missing in source data causes error

[JohnNewland]

When using a .vrt template to map GML source data to geopackage, we encounter an error if the source GML file does not contain an optional attribute expected by the .vrt:

ERROR 1: Unable to find source field 'xxx'

This might sound like expected behaviour, but we have multiple GML files and while some files will contain the optional attribute, others do not. This behaviour stops us being able to use .vrt files to process our GML.

Instead of crashing out with an error, it would be ideal to warn and continue processing. This sounds like a logic change with potential other consequences, but I feel the "nullable" attribute of <Field...> should be used to take care of ensuring required attributes exist in the data i.e. we shouldn't be relying on a crash to validate source data.

OS: Windows NT 6.2 (Server 2012)
GDAL version: GDAL 2.4.0, released 2018/12/14

Example data:
example.zip
Example error:
ERROR 1: Unable to find source field 'optionalAttribute'.

Example command line:
ogr2ogr -dsco VERSION=1.2 -f GPKG example.gpkg example.vrt -a_srs EPSG:27700 -lco SPATIAL_INDEX=NO

Thank you.

[rouault]

The current behaviour is expected. Probably the best option if we wanted to change that would be to add a acceptMissingInSource="true" attribute