html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/6836#issuecomment-1504975778,https://api.github.com/repos/pydata/xarray/issues/6836,1504975778,IC_kwDOAMm_X85ZtBui,4160723,2023-04-12T09:42:39Z,2023-04-12T09:42:39Z,MEMBER,A special-case sounds reasonable to me as well as a temporary fix before looking into if/how we can refactor groupby so that it works with multiple kinds of built-in and/or custom indexes.,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1318992926
https://github.com/pydata/xarray/issues/6836#issuecomment-1313748084,https://api.github.com/repos/pydata/xarray/issues/6836,1313748084,IC_kwDOAMm_X85OTjR0,4160723,2022-11-14T13:55:02Z,2022-11-14T13:55:02Z,MEMBER,"> we can fix that in safe_cast_to_index()

...we *cannot* fix that in `safe_cast_to_index()` (or we can add a parameter to specify the desired result).","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1318992926
https://github.com/pydata/xarray/issues/6836#issuecomment-1313739883,https://api.github.com/repos/pydata/xarray/issues/6836,1313739883,IC_kwDOAMm_X85OThRr,4160723,2022-11-14T13:49:47Z,2022-11-14T13:49:47Z,MEMBER,From #7282 it looks like we need to convert the multi-index level to a single index when casting the group to an index. And from #7105 we can fix that in `safe_cast_to_index()` (sometimes the full multi-index is expected) so we probably need a special case in `groupby`.,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1318992926
https://github.com/pydata/xarray/issues/6836#issuecomment-1255125171,https://api.github.com/repos/pydata/xarray/issues/6836,1255125171,IC_kwDOAMm_X85Kz7Cz,4160723,2022-09-22T14:39:24Z,2022-09-22T14:39:24Z,MEMBER,"Thanks @emmaai for the issue report and thanks @dcherian and @FabianHofmann for tracking it down.

There is a lot of complexity related to `pandas.MultiIndex` special cases and it's been difficult to avoid new issues arising during the index refactor.

`create_default_index_implicit` has some hacks to create xarray objects directly from `pandas.MultiIndex` instances (e.g., `xr.Dataset(coords={""x"": pd_midx})`) or even from xarray objects wrapping multi-indexes. The error raised here suggests that the issue should fixed before this call... Probably in `safe_cast_to_index` indeed.

We should probably avoid using `.to_index()` internally, or should we even deprecate it?  The fact that `mda.one.to_index()` (in v2022.3.0) doesn't return the same result than `mda.indexes[""one""]` adds more confusion than it adds value. Actually, in the long-term I'd be for deprecating all `pandas.MultiIndex` special cases in Xarray.


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