max_size and min_size validation for `forms.fields.FileField`

[amirreza8002]

Code of Conduct

• I agree to follow Django's Code of Conduct

Feature Description

hi
adding validation for max size and min size of files

Problem

since files can be uploaded by users, having some validation on them could become necessary for developers

Request or proposal

proposal

Additional Details

this was discussed in https://forum.djangoproject.com/t/proposal-max-and-min-size-validation-for-filefield/43232 and https://code.djangoproject.com/ticket/36685

we already get size of the file in the to_python method in form field and check for empty files
might just turn it into checking both side of size

Implementation Suggestions

this could be either a validator function that will be added to list of validators
or a parameter to FileField itself, which could be validated in the validate method

[github-actions]

Thank you amirreza8002 for sharing your idea! We have a lot of them so please be patient. You can see the current queue here.

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[nessita]

As mentioned in the linked ticket, this feature was requested and also discussed in #34700, #34263, #33942.

[amirreza8002]

sorry i forgot to mention the other ones 🫠

[adamchainz]

The duplicates all trace back to #33942, which was only suggesting MIME validation, and closed because of that. The file size validation seems not to have been discussed separately.

I think size validation is so lightweight and commonplace that it makes sense to include in core, on the form FileField and as separate validators. As I wrote on the forum, it's pretty surprising that Django's docs don't even contain any advice on validating a max file size, which is a very common requirement.