API to simulate QuotaExceededError

[nolanlawson]

Similar to #50, it would be awesome for fakeindexeddb to have a way to simulate the storage device running out of space and throwing a QuotaExceededError.

Currently this is really hard to repro, even in a browser (it's recommended to create a separate volume and start Chrome with that volume). Having it in fakeindexeddb would be extremely convenient.

Something like:

indexedDB.__simulateQuotaExceeded = true // false by default

[GuilleW]

With extension, a way to test all error when opening database, open transaction, etc ... will be useful too.

[GuilleW]

Something like :

indexedDB.__simulate = QUOTA_EXCEEDED_ERROR
// unit test ...

indexedDB.__simulate = CLOSE_EVENT
// unit test ...

Not API breaker and help unit testing.

[Quelklef]

Is the idea with __simulateQuotaExceeded = true to have fakeindexeddb throw an exception on the real-world quota amount?

Seems to me like it would be more useful to set the quota amount for testing (indexedDB.__quota = 50; // mb, default Infinity) or to have some way to manually throw the error (indexedDB.__throwQuotaExceeded()).

[nolanlawson]

@Quelklef This would require fakeindexeddb to actually calculate how much "storage" it's using, which would be computationally expensive and inaccurate since it's all in-memory.

The problem with throwQuotaExceeded() as a function is that, to truly simulate what a browser does, the error should be thrown during a readwrite transaction (if the quota is exceeded after opening) or in the indexedDB.open request (if the quota is already exceeded before even opening the database).

[Quelklef]

@nolanlawson Okay, that all makes sense. What is the intended behaviour of indexedDB.__simulateQuotaExceeded = true;, then? To throw on the next open request?

[nolanlawson]

That's what I was thinking – that way, you could test throwing both on open() and on a readwrite transaction, by just setting that flag right before you do the transaction.

[Quelklef]

Got it. IMO, it reads a little like setting a config option rather than setting up for imminent behaviour. Compare it to something like .__prepareExceedQuota() or another name of the likes.