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Code Issues 32 Releases Wiki Activity

Fixed #24508 -- Made annotations commutative

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This commit is contained in:
Josh Smeaton
2015-03-20 15:47:43 +11:00
parent a6bada1ee0
commit 127b3873d0
2 changed files with 20 additions and 2 deletions
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14
django/db/models/expressions.py
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@@ -238,7 +238,16 @@ class BaseExpression(object):
"""
Attempts to infer the output type of the expression. If the output
fields of all source fields match then we can simply infer the same
type here.
type here. This isn't always correct, but it makes sense most of the
time.
Consider the difference between `2 + 2` and `2 / 3`. Inferring
the type here is a convenience for the common case. The user should
supply their own output_field with more complex computations.
If a source does not have an `_output_field` then we exclude it from
this check. If all sources are `None`, then an error will be thrown
higher up the stack in the `output_field` property.
"""
if self._output_field is None:
sources = self.get_source_fields()
@@ -246,8 +255,9 @@ class BaseExpression(object):
if num_sources == 0:
self._output_field = None
else:
self._output_field = sources[0]
for source in sources:
if self._output_field is None:
self._output_field = source
if source is not None and not isinstance(self._output_field, source.__class__):
raise FieldError(
"Expression contains mixed types. You must set output_field")