forms.HStoreField crashes on an empty JSON array

[Brad Melin]

Problem: Submitting a JSON array ([]) into the default Django admin form for HStoreField (django.contrib.postgres.fields.HStoreField) throws an error.

There is some incorrect logic with the validation where if anything but a dict is passed to the to_python method, the field tries to json.load() the data and then iterate over it with value.items(). Lists don't implement this method, and so we an AttibuteError is raised.

To reproduce:

• Add an HStoreField to a model, and register that model with Django Admin.
• In the model admin edit view, insert a list into the textfield
• Submit.

Traceback: ​https://dpaste.de/bjUh

[Tim Graham]

I suppose a ValidationError should be raised instead.

[Simon Charette]

Marking as release blocker for 1.9 as this is a bug in a new feature with possible data loss on failed submission.

​PR needs minor code adjustment and a release note.

[Tim Graham <timograham@…>]

In f6517a5:

Fixed #26672 -- Fixed HStoreField to raise ValidationError instead of crashing on non-dict JSON input.

[Tim Graham <timograham@…>]

In 95ed1514:

[1.9.x] Fixed #26672 -- Fixed HStoreField to raise ValidationError instead of crashing on non-dict JSON input.

Backport of f6517a5335ccc4858ee540548a1bd162bec36c46 from master

[Tim Graham <timograham@…>]

In 3eb3186:

[1.10.x] Fixed #26672 -- Fixed HStoreField to raise ValidationError instead of crashing on non-dict JSON input.

Backport of f6517a5335ccc4858ee540548a1bd162bec36c46 from master