John Omotani

> ~~To normalise the metrics and derived quantities I think only needs:~~ > * ~~The normalisation of length~~ > * ~~The normalisation of dx, dy and dz~~ ~~Just a comment,...

> Rather than having Mesh holding the different staggered Coordinates, and having to have this callback to recalculate, would it make sense to have the staggered versions of the metrics...

Ooh, or to simplify `Mesh` as much as possible, we could have a very lightweight class to group together the staggered and unstaggered `Coordinates`, like a `CoordinatesContainer`. I'm thinking of...

> I'd like to have ways of making coordinates without a grid file, if the user of the code (or unit test) passes in the pieces needed. If we do...

> It would be really nice to be able to get rid of all the interpolation/extrapolation stuff, but I do have a small worry that removing it would make using...

Another thought - I put member variables and references rather than shared/unique pointers above, but that doesn't allow for staggered `Coordinates` not being created if they're not needed, so I...

> what tools expect certain variables in the files to be written in uppercase. @johnomotani what does xBOUT do? xarray/xBOUT are case sensitive at the moment. I guess we could...

If we went case-sensitive, how about something like this to help avoid errors: * Have an option like `strict` (true or false, default to false), that makes it an error...

> this might need to be done every time an Options operator[] is called I think it'd only be needed when (possibly) creating a new key - if the requested...

`input:strict` sounds good, and I guess `input:validate` is the same number of characters as `validate_input`, so is better. To make `validate` more discoverable, could we maybe add a command-line option...