MultiValueField should override __deepcopy__

[nick.phillips@…]

MultiValueField needs to override the default inherited from Field, as it needs to deep-copy subfields:

    def __deepcopy__(self, memo):
        result = copy.copy(self)
        memo[id(self)] = result
        result.fields = copy.deepcopy(self.fields, memo)
        result.widget = copy.deepcopy(self.widget, memo)
        result.validators = self.validators[:]
        return result

or

    def __deepcopy__(self, memo):
        result = super(MultiValueField, self).__deepcopy__(memo)
        result.fields = copy.deepcopy(self.fields, memo)
        return result

should be added to MultiValueField, if I'm right.

Without this, any "MyClass" that subclasses MultiValueField and uses subfields with complex attributes (e.g. ChoiceField's "choices") will fail when re-used within the same view.

[anonymous]

Attached patch makes sure deepcopy is called on all the sub fields

[Tim Graham <timograham@…>]

In 4e96dac450e3546bf86220932f5a64fea1ad5bac:

Fixed #19298 -- Added MultiValueField.deepcopy

Thanks nick.phillips at otago.ac.nz for the report.