(feat): Autosave using localStorage

[dobri1408]

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Closes ##4168

PR preview:

https://volto--6864.org.readthedocs.build/6864/user-manual/blocks.html#autosave

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[dobri1408]

I've updated the old pr #4252

Currently, the implementation works as follows:

1. If you close the tab or click the cancel button, an autosaved copy is stored in localStorage.
2. When you reopen the content, a toast notification informs you that a saved version is available, and you can choose to restore it.
3. If someone else has edited the content in the meantime, the toast will let you know, and you can decide whether to load your local version.
4. You can use the undo button to revert actions.
5. This behavior applies both when creating new content and when editing existing content.

I think it would be useful to start a discussion around what additional features should be included in the final version.

[dobri1408]

I've also included a video to remind you about the feature.

screen-capture.31.mp4

[stevepiercy]

Acceptance tests need to pass.

I think this is a great enhancement as is. I'd prefer to merge it after resolving failing tests. If and when we come to agreement on what additional features should be added, then we can enhance it further in separate PRs.

[stevepiercy]

I approve translation messages and change log.

It needs docs in the user manual, as a subsection in Edit content using blocks, "Autosave content". The change log, although terse, would be a good start. Screenshots or brief videos would be helpful.

It also needs a technical review from another member of @plone/volto-team.

[stevepiercy]

One final tweak on the docs (my bad), and they are good to go. I am crying tears of joy.

[stevepiercy]

Docs look good. Needs a technical review from @plone/volto-team

[pnicolli]

I definitely want to discuss how to move this forward in the volto team meeting later today. One thing to keep in mind is: does this still work if the content type schema has changed since the last time it autosaved some data? In other words, it doesn't necessarily HAVE to work, but at least it should not break. I'm saying this as a reminder also for whoever will test this, as it hit me as a possible use case but I did not go through the code yet so maybe it's handled already, I don't know.

[pnicolli]

I am testing it but honestly can't make it work. Nothing seems to be written in my localstorage therefore no toast appears.

EDIT: scratch all this comment, I was working on an item that was broken in the backend. It's working now, I'll keep testing.

[pnicolli]

First comment is: it's suggesting me to restore the autosaved data even if it's empty, would be great if it didn't, if at all possible.

To reproduce:

1. add a page
2. populate the title
3. cancel and edit again
4. apply autosaved data
5. empty the title
6. cancel and edit again
7. it suggests autosaved data, if you apply it it's empty

[pnicolli]

A couple other thoughts:

1. it would probably be even better if we allowed users to clear autosaved data for a page in addition to just refusing to apply it, otherwise they will continue to show up until you actually save something
2. should we consider having some cleanup mechanism to avoid cluttering the localStorage? I'm not even sure if this is the case, just wondering
3. Every feature/idea I'm suggesting here and in previous comments can definitely become a separate issue if you want, instead of blocking this big PR even more. As I said in the Volto Team Meeting yesterday, this is the kind of PR that can become a mess if it sits here for a while.

I'll review the code shortly as well, the baseline feature is working fine for me when run locally.

[pnicolli]

Awesome, needs a little cleanup and then it's good to go

[sneridagh]

LGTM!

I am not 100% sure about the messages still, but let's test drive it during the alpha, and improve on the go.