TypedChoiceField does not properly coerce 'None' in certain circumstances

[anonymous]

class MyModelAdmin(admin.ModelAdmin):
	def formfield_for_dbfield(self, db_field, **kwargs):
		if db_field.name == 'integerfield':
			return forms.TypedChoiceField(choices=((None,'Undecided'),(-1, 'Reject'), (0, 'Neutral'), (1,'Accept')))

Selecting 'Undecided' here results in the error message "'None' must be an integer"

In order to fix this I have to add the following param to TypedChoiceField:

coerce=lambda v: int(v) if v and v != 'None' else None

If I try this instead it results in the error "Select a valid choice. None is not one of the available choices.":

coerce=lambda v: int(v) if v else None

It appears that the None choice is getting coerced to a string before it passes into TypedChoiceField.to_python (or wherever it gets passed to first)?

[Tim Graham]

This may be addressed in master (1.7) with #20649 - could you take a look and see if that meets your use case?

[Claude Paroz]

That change: ​https://github.com/django/django/commit/1123f4551158b7fc65d3bd88c375a4517dcd0720#diff-aee6730bae795d31efec3c5d014804a9R511
...should solve your issue, as the None choice will be rendered as the empty string in the option value, then coercion should consider it as the empty value. Reopen if you can reproduce an issue with master code.