added extra error checking on spherical mesh creation

[chrwagne]

Description

Adding an additional check to ensure r_grid, phi_grid, and theta_grid values make sense when creating a spherical mesh, and raise a Value Error when they do not. This way a Value Error will be raised when a user creates attempts to create a spherical mesh with a r_grid, phi_grid, or theta_grid minimum that is greater than or equal to the maximum.

Fixes # 2933

#2933

Checklist

• I have performed a self-review of my own code
• I have followed the style guidelines for Python source files (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[chrwagne]

@shimwell I have made these changes for my added error checks on the spherical mesh. Could you review them please?

[shimwell]

This looks super nice and concise. Very tidy PR. I could only spot a couple of extra f chars.

This looks ready to go in my view. I think we should merge this one in before #2977 then perhaps #2977 can be reshaped a bit to make use of the utility code here in the checkvalue.py

[shimwell]

@paulromano would it be ok to merge this extra check in. Admittedly it will slow down the mesh creation a bit. Do you think the reduction in speed is worth the extra user friendliness? Would it be worth trying a numpy solution to speed things up a bit for the longer arrays?

[shimwell]

Thanks for those changes, I've triggered the CI

[shimwell]

CI has passed

[paulromano]

I like the idea here but the implementation is not very efficient. I would recommend using numpy functionality rather than an explicit for loop. You can check for monotonicity of a list/array with:

np.all(np.diff(value) > 0.0)

[chrwagne]

@shimwell @paulromano Thanks for the response and numpy changes applied!

[paulromano]

Thanks for this improvement, @chrwagne! Sorry for the delay on getting this merged.