#30548: Improve exception message when BaseExpression raises "'Expression
contains
mixed types. You must set output_field.'"
-------------------------------------+-------------------------------------
Reporter: Keryn | Owner: nobody
Knight |
Type: | Status: new
Cleanup/optimization |
Component: Database | Version: master
layer (models, ORM) |
Severity: Normal | Keywords: expressions orm
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
The
[https://github.com/django/django/blob/661e6cc2c97d9bcb45198be787409488e1825c90/django/db/models/expressions.py#L290
source which raises the exception] has enough information to say both what
types were found, and which of those were unexpected, **and** probably
have a useful `repr()`
In the test suite, the unexpected output types encountered seem to be
`DurationField` and `IntegerField`, so a more thorough message might be
something like:
`Expression repr(self) contained mixed types: DateField, DurationField.
DurationField was unexpected; you must set the output_field= for this
Expression to either DurationField(), DateField() or ...` (''??? I dunno,
some concrete explanation of what the output_field has to be/implement if
you're not going to use any of the builtins'')
The merit of including the repr is arguable, as the `Expression` may not
what the user put in (eg: in the test suite it always seems to be a
`CombinedExpression(lhs, connector, rhs)`) but it gives more of a hint in
a query which contains multiple expressions (either nested or separate) as
to which one is actually causing the problem vs just being told "something
was wrong. Put an output_field= everywhere until it ceases, your guess is
as good as mine"; at the very least the word Expression could be replaced
with the class name which is actually raising it.
--
Ticket URL: <https://code.djangoproject.com/ticket/30548>
Django <https://code.djangoproject.com/>
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