Fix mv-init is not applied when storage returns ""

[lukesmurray]

This is to fix #438. I believe this works and is DRY. My only gripe is that I used serialized + "" in two places. If you want I can extract that into a variable.

[lukesmurray]

not sure if the extra conversion to a string is necessary here

[LeaVerou]

It is not, JSON.parse() converts to a string internally anyway. You can quickly verify this by typing e.g. JSON.parse(false) in the console. :)

[LeaVerou]

Hi Luke!

Thanks for contributing!
The issue here is that if there's no init backend, this will still propagate as an error, but it is not. Having no data is a normal initial state of any app.

I think a better process would be to return null from .catch() when there is an init backend and in a subsequent .then() load from the init backend if data is null. What do you think?

Btw, very minor, but you may want to set your editor to remove trailing whitespace, I see there's a tab added in the end of line 490.

[lukesmurray]

not sure if we need to change the backend variable here.

[lukesmurray]

Sorry I committed early I still haven't fixed the issue 👎

[lukesmurray]

Ok so I think this fulfills what you were asking for but the error is still propagated.
The part I'm confused about is what we want to do in mavo#load when the data is null and there is no init. Do we want to suppress any errors in that case and assume that the backend is empty?

[LeaVerou]

The part I'm confused about is what we want to do in mavo#load when the data is null and there is no init. Do we want to suppress any errors in that case and assume that the backend is empty?

Yes. It's not an error, most apps start with no data! If there's an init backend we load from there, if not, no problem, we just render null!

[LeaVerou]

Hi Luke,

This is not quite what I suggested. As you point out, it still throws an error when the data is null which propagates further if there's no init backend. As I explained in my comment, the data being null is not an error condition.

A few notes that may be helpful:

• We want the init backend to be used in two cases: a) When there is an error and b) when the data is null (which is not an error and should not throw)
• If there's no init backend and the data is null, we just render null, no problem.
• Right now (before any PRs), the init backend is only utilized in a .catch(), i.e. when an error has occurred and nulls are treated as errors which are just caught in that catch or propagated and caught in the next one. Do note that this is unavoidable for some backends, notably file-based ones, since the file will often not be found when there's no data yet and will yield an HTTP 404 error (which is special cased later on in this method).
• Do note that even when there's an actual error that we display to the end user, we still render null.

[LeaVerou]

Hi Luke,
Are you still interested in working on this? Do you need help?

Cheers,
Lea

[lukesmurray]

@LeaVerou better late than never. This passes the tests you wrote. I did what you suggested.

1. removed the error I added for when the backend loads a null value.
2. return null from the first catch if the backend load throws an error and init exists
3. add a then which attempts to load with init if the data is null and init exists.
4. propagate null in the new then if init does not exist.

I can squash these commits if you want me to.