#20202: BaseModelForm uses model_to_dict to provide initial, causes problems for
ModelChoiceField with non-pk to_field_name
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Reporter: valtron2000@… | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 1.5
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Changes (by bmispelon):
* cc: bmispelon@… (added)
* needs_docs: => 0
* needs_better_patch: => 0
* needs_tests: => 0
* stage: Unreviewed => Accepted
Comment:
This definitely looks like a bug but it might be a bit tricky to fix (it
will at least require some changes to `model_to_dict`'s signature).
As noted, the issue is that `model_to_dict` will always return the primary
key of the model, not taking into account the field's `to_field_name`
attribute.
The problem is that `model_to_dict` does not have access to the form's
fields: it only gets passed the instance, a list of strings corresponding
to the model's fields present in the form, and a list of strings of the
fields to exclude. Therefore, it has no way to access the `to_field_name`
attribute and adjust the value accordingly.
On a side-note, it seems that `ModelChoiceField.to_field_name` is
completely undocumented, though there seem to be a few tests for it.
This ticket could be a good excuse to finally document it.
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Ticket URL: <https://code.djangoproject.com/ticket/20202#comment:1>
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