Fixed #35384 -- Raised FieldError when saving a file without a name to FileField.

[jonnythebard]

…nce to File field

Trac ticket number

ticket-35384

Branch description

Added code for raising FieldError when trying to save ContentFile instance to File field.

• The issue originates from pre_save of FileField class.
  • when pre_save get's called to save file-like objects, it checks if file is truthy.
    
  • File truthy is determined by the following
    
  • When using regular File or ImageFile instance, even if they do not have explicit name, name would be retrieved from there actual file. But ContentFile instance has nowhere to get its name and its name is set to None.
  • Thus, It cannot pass the if statement(if file and not file._committed:) which results in pre_save method to silently drop it's duty.
• I suppose pre_save is adequate location to validate if ContentFile.name because looks like it is responsible for letting the file objects to be passed to file storage manager.
• Simply adding if file.name is None: would affect many other functioning codes.
  • File fields with null=True option will fall into this statement as well
• Besides None, it is Needed something to represent a ContentFile.name is empty.
• I added EmptyName class and made it default if ContentFile.name is not passed.
• The following at pre_save works fine.
  

Thanks to @john-parton for a good description and isolated tests.

Checklist

• This PR targets the main branch.
• The commit message is written in past tense, mentions the ticket number, and ends with a period.
• I have checked the "Has patch" ticket flag in the Trac system.
• I have added or updated relevant tests.
• I have added or updated relevant docs, including release notes if applicable.
• I have attached screenshots in both light and dark modes for any UI changes.

[sarahboyce]

This will also need a release note 👍

[jonnythebard]

This will also need a release note 👍

Could you provide me with the guide on how to write release note?

[sarahboyce]

This will also need a release note 👍

Could you provide me with the guide on how to write release note?

Actually as this is a bug fix, we won't need a release note here. So don't worry 😁

[jacobtylerwalls]

👋 @jonnythebard spotted a typo in the PR title, would you mind fixing?

[jonnythebard]

It looks like part of the fiddly part is that FieldFile.delete would set name to None in order to delete when saving.

I added a test for deleting the field filed to check if any error occurs.

[adamchainz]

A couple smaller improvements. Looking good!

[jonnythebard]

Thanks for the comments🙏 @adamchainz

[sarahboyce]

Thank you @jonnythebard 👍
I've pushed minor updates. I will give the other a chance to make comments on these before I merge