Add warning about polynomial degree 0

[benegee]

I was misled by a comment in basis_lobatto_legendre.jl, thinking polydeg = 0 would be an exceptional but valid setting. It however only works with TreeMesh. See https://github.com/trixi-framework/Trixi.jl/pull/1489

So I extended the comment.

Would there be an easy way to catch such a setting early and warn users?

[github-actions[bot]]

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[benegee]

Would we want to have such checks? What is our policy in regard to user assistance?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.30%. Comparing base (4bf61a0) to head (607c70a). Report is 3 commits behind head on main.

Additional details and impacted files

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[ranocha]

Would we want to have such checks? What is our policy in regard to user assistance?

I would be fine having such a check. Right now, we just check that the dimensions fit

https://github.com/trixi-framework/Trixi.jl/blob/b11bc10d8ac68798ae2e53f9db3d5c4f824af5fa/src/semidiscretization/semidiscretization_hyperbolic.jl#L44

What about the other core devs, e.g., @trixi-framework/principal-developers?

[sloede]

Intuitively, I am not a big fan. One would have to add mesh-specific checks to the semidiscretization, which I don't think is good practice regarding modularity and extensibility.

[ranocha]

Good point.