DB: drop before import & handle errors

[obfusk]

• drop data before importing
• make sure all (database) errors are handled properly
  • add DBException class
  • throw DBException in DB functions
  • catch DBException instead of mostly ignoring return values
• make sure unit tests pass
• superficial testing
  • add/edit card/group works normally
  • import/export
• warn user about data being dropped
• FIXMEs
  • remove toasts considered unnecessary (some should never happen)
  • make sure toasts are called with the right context parameter
  • translate untranslated strings
  • improve error messages
  • confirm control flow is still correct
  • Assert.fail(): add error messages?
• review
• more testing

#1333 should be rebased on this.

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Nice to have

• python script to merge two exports? https://github.com/obfusk/catimerge

[TheLastProject]

This change is way too big I feel, definitely too big to be one single commit.

Imho, we want to fix the importer separately. The whole editing cards and everything has been working fine for years and years on end, I'd rather not touch that without very good reason.

It would be better to just start with 1 commit to drop the DB before importing an export, especially because that code wouldn't touch any of the rest of the DB handling, it would live solely in the importing code.

[obfusk]

It would be better to just start with 1 commit to drop the DB before importing an export, especially because that code wouldn't touch any of the rest of the DB handling, it would live solely in the importing code.

Sure. That's easy to separate. I'll make a separate PR for that then.

But you also wanted to stop silently ignoring errors IIRC. Which is what the rest of the PR does. And that requires a lot of changes, though they are all pretty much the same.

[TheLastProject]

I guess we misunderstood each other there, I specifically meant that Catima silently ignores errors during importing (conflicts with other cards being the primary issue). The importing is where stuff is in really bad shape, the general DB handling seems... not pretty but functional.

I want Catima to handle imports well: detect conflicts and tell the user. However, until that time, wiping the DB before starting the import is the easier fix.

[obfusk]

I get that. The problem is that importing uses the same functions as the rest of the app.

I don't think you want the complexity of having an API with and one without errors.

But I can change it so that the rest of the code catches the errors but just ignores errors like before.

And I can do it in more commits, one function at a time.

Just let me know how you'd like to proceed.

Will start with a PR just for the DB drop + warning message.

[obfusk]

I want Catima to handle imports well: detect conflicts and tell the user. However, until that time, wiping the DB before starting the import is the easier fix.

Agreed. I did write a script to merge two ZIP exports: https://github.com/obfusk/catimerge
Also not the best solution, but it works right now :)