Opened 3 years ago

Closed 3 years ago

#20948 closed Uncategorized (invalid)

Form ImageField, MemoryFileUploadHandler and reading content of the InMemoryUploadedFile

Reported by: p_hrechyshkin@… Owned by:
Component: Python 2 Version: 1.4
Severity: Normal Keywords: file upload
Cc: p_hrechyshkin@… Triage Stage: Unreviewed
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

There is a form with ImageField, which returns validation error

"Upload a valid image. The file you uploaded was either not an image or a corrupted image."

In my view I am trying to read image file content:

image = self.request.FILES.get('image')
if image:

content = "".join(image.chunks())

Validation error doesn't occur if I comment line with image.chunks(), also it isn't showed if I remove "django.core.files.uploadhandler.MemoryFileUploadHandler" from FILE_UPLOAD_HANDLERS setting.

So the reason could be in file object created by MemoryFileUploadHandler (InMemoryUploadedFile).

My guess was it could be that after read there is no call file.seek(0) which set file reader pointer to the begging of the file.

It could be ImageFile.to_python assumes that pointer set to the beginning.
In ImageField.to_python I have added

data.file.seek(0)

before

file = StringIO(data.read())

and I haven't got image validation error after that.

Is it proper behavior? Or ImageField shouldn't assume that file haven't been read? Or InMemoryUploadedFile should call file.seek(0) after chunks iterator ended its work?

Change History (4)

comment:1 Changed 3 years ago by Florian Apolloner

Needs documentation: unset
Needs tests: unset
Patch needs improvement: unset

You are supposed to call image.seek(0) yourself after you read from it. That said, it would be intresting to know why it works for TemporaryUploadedFile

comment:2 Changed 3 years ago by sduveen

Owner: changed from nobody to sduveen
Status: newassigned

comment:3 Changed 3 years ago by sduveen

Owner: sduveen deleted
Status: assignednew

comment:4 Changed 3 years ago by Tim Graham

Resolution: invalid
Status: newclosed
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