osgeo.ogr.Feature.ExportToJson() error

[doug]

Getting this error: ../osgeo/ogr.py", line 2398, in ExportToJson

'geometry': self.GetGeometryRef().ExportToJson(as_object=True),

TypeError: ExportToJson() got an unexpected keyword argument 'as_object'

Patch attached.

[warmerdam]

Even / Howard,

Does this make sense? Do we depend on an external json package that has changed names?

[Even Rouault]

The Feature.ExportToJson() was added as part as #1891, so Howard / Chris Schmidt are the reference here ;-)

My understanding of the situation....

0) The patch is not appropriate in its current form since it patches a generated file. It should be a patch in swig/include/python/ogr_python.i instead

1) The issue is that Feature.ExportToJson() seems to be broken and I doubt it has ever worked properly. It relies on a non existing mode of Geometry.ExportToJson() that would export the geometry as a Python object hierarchy instead of a string (the call to self.GetGeometryRef().ExportToJson(as_object=True)). Hence the hack in the proposed patch to add a kwargs argument to Geometry.ExportToJson(), but that's not the correct solution. A possible fix would be deserialize the geometry json string with json.loads()/simplejson.loads().

2) The json / simplejson thing is a bit clearer. According to ​http://docs.python.org/library/json.html and ​http://pypi.python.org/pypi/simplejson/ , simplejson was the only existing solution (as an external optional module) until python 2.6 appeared. Since python 2.6, there's a builtin json module available. So that part of the patch makes sense. Python >= 2.6 has always json, but not necessarily simplejson. However the usefulness of that part is a bit mitigated by point 1)

I suggest the attached patch instead, which also fixes an exception when the feature has no geometry.

[Even Rouault]

Fixed version of the initial proposed patch

[doug]

Replying to rouault:

The patch is not appropriate in its current form since it patches a generated file.

Agreed.

I'm new to GDAL and not familiar with how the python lib is built, but when I saw this code I knew it needed a patch. It was only afterward I realized I submitted a patch for generated code.

The activity on this ticket is great and it inspires strong confidence in the code. Thanks all.

[Even Rouault]

Patch commited in r21216. Test added in r21217