Opened 5 years ago

Last modified 5 months ago

#13750 assigned Bug

ImageField accessing height or width and then data results in "I/O operation on closed file"

Reported by: ROsborne Owned by: aethemba
Component: File uploads/storage Version: 1.2
Severity: Normal Keywords:
Cc: aethemba Triage Stage: Accepted
Has patch: yes Needs documentation: no
Needs tests: no Patch needs improvement: yes
Easy pickings: no UI/UX: no

Description (last modified by Alex)

If you have a simple model with an ImageField, the following code will fail with a "I/O operation on closed file":

instance = MyClass.objects.get(...)
w = instance.image.width
h = instance.image.height
original = Image.open(instance.image)

The work around is to reopen the file:

instance = MyClass.objects.get(...)
w = instance.image.width
h = instance.image.height
instance.image.open()
original = Image.open(instance.image)

Note this is different than the issue of the 2nd read() returning empty strings for two reasons:

  1. You can not seek(0), the file is closed.
  1. Needing to reopen in this case is unexpected.

Attachments (7)

regression_13750.diff (1.3 KB) - added by aethemba 6 months ago.
Test to replicate the behaviour described in the ticket
13750_simple_approach_solution.diff (514 bytes) - added by aethemba 6 months ago.
Simple approach to solve #13750
13750_tests.txt (34.1 KB) - added by aethemba 6 months ago.
Results of tests with simple solution
13750_tests_2.txt (3.2 KB) - added by aethemba 6 months ago.
Updated test results
13750_test_simple_solution.diff (2.1 KB) - added by aethemba 6 months ago.
Updated changed code
13750.diff (1.8 KB) - added by aethemba 6 months ago.
Documentation for behavior and updated regression test
13750_new_patch.diff (2.7 KB) - added by aethemba 5 months ago.
Latest patch

Download all attachments as: .zip

Change History (26)

comment:1 Changed 5 years ago by Alex

  • Description modified (diff)
  • Needs documentation unset
  • Needs tests unset
  • Patch needs improvement unset

Reformatted description. Next time please use preview and consult WikiFormatting.

comment:2 Changed 5 years ago by russellm

  • Triage Stage changed from Unreviewed to Accepted

comment:3 Changed 5 years ago by russellm

#13874 is a different presentation of the same problem.

comment:4 Changed 4 years ago by julien

  • Severity set to Normal
  • Type set to Bug

comment:5 Changed 4 years ago by aaugustin

  • UI/UX unset

Change UI/UX from NULL to False.

comment:6 Changed 4 years ago by aaugustin

  • Easy pickings unset

Change Easy pickings from NULL to False.

comment:7 Changed 6 months ago by aethemba

  • Owner changed from nobody to aethemba
  • Status changed from new to assigned

Changed 6 months ago by aethemba

Test to replicate the behaviour described in the ticket

Changed 6 months ago by aethemba

Simple approach to solve #13750

comment:8 Changed 6 months ago by aethemba

Would it be a problem to simply open image files (specifically ImageFieldFile objects) in the _get_ function of the FileDescriptor object? Please see the "simple approach" attachment with a potential diff.

Currently, it fixes the new regression test but approximately 31 other tests fail because they test for the "open-ness" of a file. However, these failing tests could be adapted if people agree to this solution. (See 13750_tests.txt)

I'm happy to hear people's suggestions or other feedback.

Changed 6 months ago by aethemba

Results of tests with simple solution

comment:9 Changed 6 months ago by aethemba

  • Cc aethemba added

comment:10 follow-up: Changed 6 months ago by timgraham

How would the tests be adapted? Where is the file closed in the first place?

Changed 6 months ago by aethemba

Updated test results

Changed 6 months ago by aethemba

Updated changed code

comment:11 Changed 6 months ago by aethemba

I've updated the patch code and I've added the updated test results.

Some tests are now failing because they expect the imagefile to be closed (e.g., tests/modelfields/test_imagefield.py line 165, after getting the size of an image).

I'm assuming that, given the description in this ticket, we want to retrieval of the image (and not an image property) to leave the file open. Is that a correct assumption? And if so, isn't that rather inconsistent behaviour?

comment:12 in reply to: ↑ 10 Changed 6 months ago by aethemba

Replying to timgraham:

How would the tests be adapted? Where is the file closed in the first place?

Hi Tim, I've updated my proposed solution code and test results as attachments. I also left some new questions. Lastly, the file get's closed during saving.

comment:13 Changed 6 months ago by collinanderson

  • Has patch set

comment:14 Changed 6 months ago by timgraham

  • Patch needs improvement set

I don't see a compelling reason to automatically open the file. That change would be backwards incompatible for anyone who is accessing other attributes but doesn't care about the image (they would now have to close it). Can we simply document the behavior in docs/topics/files.txt?

comment:15 Changed 6 months ago by aethemba

Yeah, while I understand the issue of the ticket reporter, keeping things as they are makes more sense to me because the behaviour would remain consistent. As a next step, I could adapt the regression test to test for an image to be closed and include an entry in docs/topics/files.txt. Unless, of course, someone else does have good reasons to open the file.

Changed 6 months ago by aethemba

Documentation for behavior and updated regression test

comment:16 Changed 6 months ago by aethemba

I updated the regression test to check the behaviour that accessing an image field of a model returns a closed file-like reference. Furthermore, I updated the documentation in docs/topics/files.txt. Changes have an accompanying PR to master. Looking forward to the feedback.


comment:17 Changed 5 months ago by aethemba

  • Patch needs improvement unset

I took another look at this issue and found some other interesting stuff. I noticed that, when not accessing the width or height property, the call to Image.open(model.image) does pass successfully. I may have been looking at the wrong thing.

I dug a little deeper and I found that in django/core/files/images.py the function get_dimensions() has a "close" keyword argument. This keyword argument comes from a call to self.closed in the ImageFile class (a few lines above). In the "get_image_dimensions" function, however, the "close" keyword argument determines whether a file should be closed at the end of the function. I think that was not correct, because if self.closed returns True, the keyword argument to the function is "close=True" and there is a call to file.close() at the end of the function get_image_dimensions.

As a solution, I removed the "close" keyword argument in "get_image_dimensions" and added a variable "close" that is either True or False depending on whether in the beginning of the function the file is explicitly opened.

I also re-added the regression test that caused the "I/O operation on closed file" error. With the new patch this test now passes and so do all the other tests. I updated my PR to the repo and removed the documentation bit of my previous patch.

Changed 5 months ago by aethemba

Latest patch

comment:18 follow-up: Changed 5 months ago by timgraham

  • Patch needs improvement set

Still not sure the patch is ideal as noted on the pull request. By the way, there's no need to attach the patch to the ticket if you send a pull request.

comment:19 in reply to: ↑ 18 Changed 5 months ago by aethemba

Replying to timgraham:

Still not sure the patch is ideal as noted on the pull request. By the way, there's no need to attach the patch to the ticket if you send a pull request.

Hey Tim,

thanks for the feedback, much appreciated. I'm a bit confused though:

"Can you make this work adding self.assertTrue(profile.image.closed) after this line? I wouldn't expect accessing the image dimensions to leave the file opened."

Isn't that contradicting with the original complaint of the ticket? If I close the file after accessing the height or image the regression test will fail because a closed file will throw the IO error when passed to an Image.open().

I'm not sure which direction to take to resolve this issue correctly.

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