Implement destructoring nested tuples on "let" and "for" statement target

[Kijewski]

This PR implements the parsing of nested tuples for the target of {% let %} statements. E.g.

{% let (a, (b, c)) = … %}

[Kijewski]

If this PR is accepted, my next two PRs will

1. introduce destructoring structs on the lhs, and
2. the use of the same function for "match" / "if let" targets.

[vallentin]

Nice 🎉

Didn't look at the diffs yet, but from the title I assume it doesn't apply for e.g. for (a, (b, c)) in ...? Can the same parsing and generation be applied to that? Would be nice, as then the last point in #451 can be closed :)

[Kijewski]

"for … in" uses the new parsing function: https://github.com/djc/askama/pull/506/files#diff-48297b9b3a3f70c8521bedbaa0601f9e2b405eaa7a99fbffe0d9131e3207e478L904-L907

I'll add a test for nested tuples in for-loops.

[vallentin]

So, that's a yes. Nice 🎉

It's much appreciated, that you've arrived and implemented all these nice to have features :)

[Kijewski]

Hehe, you're welcome. Well, the library is well written, you guys answer fast, so it's quite easy to contribute.

Please have a look at the added test if I understood #451 correctly.

[vallentin]

you guys answer fast

That's probably mostly due to luck + all of us being in the same timezone.

Please have a look at the added test if I understood #451 correctly.

Yes, that looks great. Optionally, a simple .iter().enumerate() might also be nice, as a simple base case test. :)

[vallentin]

Here's a few comments :)

[Kijewski]

I applied your suggestions.

[djc]

The scond commit looks great, but I can't quite make sense of what's going on with the first one. Left a bunch more specific questions/suggestions, below.

[Kijewski]

I split the 1st commit into 6 commits. :-/ → #510

[Kijewski]

Rebased on #510.

[Kijewski]

Rebased on main. I could not reproduce the error in askama_rocket at home.

[djc]

Yeah, I think the askama_rocket issue was a recent nightly regression. I think it has already been fixed, so hopefully it will disappear soon.

[djc]

Thanks!