django.contrib.gis.gdal.DataSource fields give gibberish or segfault when accessed directly

[YenTheFirst]

if you hold a feature in a variable, and access a field, it will give the correct value.

however, if you access a feature's field by layer[<index>][<field_name>], it gives gibberish, or a segfault.

this might be related to https://code.djangoproject.com/ticket/9448. however, given that the ticket was closed, it might be a different issue.

script to reproduce issue:

import os
import django.contrib.gis
from django.contrib.gis.gdal import DataSource
 
GIS_PATH = os.path.dirname(django.contrib.gis.__file__)
CITIES_PATH = os.path.join(GIS_PATH, 'tests/data/cities/cities.shp')
 
ds = DataSource(CITIES_PATH)
layer = ds[0]
feature = layer[0]
field = feature['Name']
 
print "this is valid: %r (%r)" % (field.value, list(field.value))
 
field = layer[0]['Name']
 
print "but this isn't: %r (%r)" % (field.value, list(field.value))

in python, results in segfault.
in ipython:
this is valid: 'Pueblo' (['P', 'u', 'e', 'b', 'l', 'o'])
but this isn't: ':\xd5\xe2=\xb1\xb4\xb9\xb4Q' ([':', '\xd5', '\xe2', '=', '\xb1', '\xb4', '\xb9', '\xb4', 'Q'])

saved as script, results in:
this is valid: 'Pueblo' (['P', 'u', 'e', 'b', 'l', 'o'])
but this isn't: ([])

this is on an ubuntu 11.04, with django 1.4, and gdal 1.7

[Claude Paroz]

Add parent references to GDAL Feature/Field

[Claude Paroz]

Confirmed. It appears that it is the same type of issue as in #9448. At least, adding references to parent objects seems to solve the problem.

[jbronn]

Yeah this is a problem. I've updated the implementation, but will need to review more when I get home from the sprints.

[Claude Paroz <claude@…>]

In cb9f71dd99f0e524c871830b248cf28fcacd5753:

Fixed #18640 -- Allowed access to GDAL Feature without Datasource

Thanks Justin Bronn for improving my initial patch.