#25493: Model instances created with unittest.mock can raise confusing errors
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Reporter: jarshwah | Owner: nobody
Type: Bug | Status: new
Component: Database | Version: 1.9a1
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Django can raise one of the following
- `ValueError: Failed to insert expression` or;
- `ValueError: Failed to insert expression "<MagicMock
name='create().id.resolve_expression()' id='139633074508184'>" on
fundraising.Payment.stripe_charge_id. F() expressions can only be used to
update, not to insert.`
when using unittest.mock to mock the creation of an object. The
djangoproject.com tests began throwing errors. Tim fixed these problems in
this PR: https://github.com/django/djangoproject.com/pull/524
The PR adds return values for the id of columns that are used to create
new instances to avoid these errors.
What I think is happening is that the lack of id is somehow causing the
mock to be treated as a `Col`. The existence of a `Col` in a
`objects.create()` call is what triggers the confusing error message.
Since no `F()` expression has been used by the user, tracking down the
cause is difficult.
We should try and figure out why the mock is being resolved to a Col and
stop that from happening or improve the error message if that's not
possible.
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Ticket URL: <https://code.djangoproject.com/ticket/25493>
Django <https://code.djangoproject.com/>
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