[Django] #18283: FileField should not reuse FieldFiles
Django
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Reporter: sayane | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.4
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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A simple example:
{{{
old_image = mymodel.image
old_image.open()
try:
mymodel.image = do_something_with_image(old_image)
finally:
old_image.close()
mymodel.save() # transaction manager is in auto commit mode
old_image.delete()
}}}
'''Expected behavior:'''
New file is commited to disk and database, old file is removed.
'''Actual behavior:'''
New file is commited to disk and database, then this new file is removed
from disk.
That's because FileField (or to be more precise: FileDescriptor class) is
re-using FieldFile objects instead of creating new FieldFile for every new
instance of a file. This leads to unexpected results and data loss (like
in example).
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Ticket URL: <https://code.djangoproject.com/ticket/18283>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
Type: Bug | Status: new
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: | Needs documentation: 0
Has patch: 0 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Changes (by jezdez):
* needs_better_patch: => 0
* needs_docs: => 0
* needs_tests: => 0
* stage: Unreviewed => Accepted
--
Ticket URL: <https://code.djangoproject.com/ticket/18283#comment:1>
Django
Reporter: sayane | Owner: szopu
Type: Bug | Status: assigned
Component: Database layer | Version: 1.4
(models, ORM) |
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
Changes (by szopu):
* owner: nobody => szopu
* status: new => assigned
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Ticket URL: <https://code.djangoproject.com/ticket/18283#comment:2>
Django
Reporter: sayane | Owner: trg
Type: Bug | Status: assigned
Component: Database layer | Version: 1.4
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Changes (by trg):
* owner: szopu => trg
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Ticket URL: <https://code.djangoproject.com/ticket/18283#comment:3>
Django
Reporter: sayane | Owner: trg
Type: Bug | Status: assigned
Component: Database layer | Version: 1.4
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Easy pickings: 0 | UI/UX: 0
Comment (by trg):
I have a real trouble with reproducing this bug. The description of it is
very enigmatic - the submitter didn't mention what
`do_something_with_image()` actually does (for instance, what type of
object it returns).
This bug seems to happen only when one takes the `FieldFile` object from
specified model field and modifies it in place. This is illustrated by
`test_unchanged_fieldfile` in the diff below:
https://github.com/django/django/compare/master...szopu:ticket_18283?expand=1
The only way I see this problem can be fixed, is defensive shallow copying
of the `FieldFile` object in `__get__` and `__set__` (I think that doing
it for `__set__` only is not enough). But this solution has a downside,
for instance, this would generate following semantics:
{{{#!python
model.myfile.name = 'somefile.txt'
print(model.myfile.name) # returns the previous filename instead of
'somefile.txt'
}}}
So my question is: Is it the right way to go?
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Ticket URL: <https://code.djangoproject.com/ticket/18283#comment:4>