Saving DataTree to zarr changes the order of the groups

[bweeding]

What is your issue?

When I generate a DataTree and save it to a zarr file, the order of the groups is not preserved.

This is irritating as I had ordered the DataTree in a particular way for automated plotting.

[TomNicholas]

I don't think zarr is guaranteed to preserve order. Zarr's list operation is the result of an async list, which can return results in any order (needed for scalability). The best zarr could do would be to always sort that list before returning it, but that still wouldn't allow you to create an arbitrary order (i.e. insertion order) and round-trip it like you are trying to here.

ordered the DataTree in a particular way for automated plotting.

I'm curious why the ordering of groups would matter for plotting? Ordering of groups doesn't really mean anything in DataTree...

[bweeding]

Ok, no worries.

It came up as a had a plotting routine comparing climate model outputs and I was iterating through the groups using indices rather than keys, but I've fixed that now so it's no longer a problem.