Add / Edit forms - Any way to preserve file uploads when form validation errors occur?

[neilferreira]

Hello

Before I spend too much time digging through the code I figured I'd ask if anyone has already covered this. If I go to add or edit an object that has a NamedBlobImage field on it I can see a file upload widget. If I specify a file but another form validation error occurs my uploaded file is lost. This is particularly frustrating if the upload takes a long time to upload in the first place.

Is there any way to configure the Dexterity forms to not lose the uploaded files when a validation error occurs?

Thankyou.

FYI, I'm using Plone 4.3.

[davisagli]

I don't think there's currently any infrastructure to handle this, but it would be a really nice feature to have.

SubstanceD does this by putting the files in a temporary directory and a reference to them in the user's session: https://github.com/Pylons/substanced/blob/master/substanced/form/__init__.py

In order to use that approach for Plone we'd want to use a session mechanism that doesn't write to the ZODB temporary store (which tends to cause conflicts and requires setting up session affinity in your load balancer). Maybe a signed cookie.

[datakurre]

We could do this with plone.app.drafts. I added a simple Dexterity-support for it for Mosaic, but this particular use case is not yet supported (it auto-saves values on validation, but only when the validation passes; also it does not re-use auto-saved values on final save, which would be the case here).

Plone.app.drafts does not require Mosaic. It is activated for content types by enabling drafting behavior.

Plone.app.drafts tries to avoid conflicts by making separate draft BTree for each authenticated user.

[gforcada]

Couldn't this actually be handled by either session/local storage (HTML 5 new thingies)?

[davisagli]

Maybe, but:

• local storage typically has a fairly small size limit
• it'd be nice to avoid sending the file to the server more than once, if it's a large file

[mauritsvanrees]

File uploads are preserved now, at least in Plone 5.2. I remember I have seen that, but I don't remember in which package this was done.
@thet You created this feature. Which package was that?