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/5738#issuecomment-906792475,https://api.github.com/repos/pydata/xarray/issues/5738,906792475,IC_kwDOAMm_X842DI4b,1217238,2021-08-26T22:46:19Z,2021-08-26T22:46:19Z,MEMBER,"In the long term, I think we want to eliminate any requirements in Xarray's data model about what variables names are OK.

In particular:
1. We want to allow a coordinate named `""foo""` with different dimensions than `(""foo"",)`, in order to support reading all possible netCDF files into xarray.
2. We want to allow indexing with coordinates that are not dimensions.

With this second change in particular, it should not be a problem to have a multi-index level with the same name as a dimension.

It is true that this change will introduce an inconsistency between appropriate keys for use with `sel` (indexed coordinates) and `isel` (dimensions). But I think this is basically inevitable.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,979316661
https://github.com/pydata/xarray/issues/5738#issuecomment-906201836,https://api.github.com/repos/pydata/xarray/issues/5738,906201836,IC_kwDOAMm_X842A4rs,4160723,2021-08-26T08:25:47Z,2021-08-26T08:25:47Z,MEMBER,"My initial thoughts was to opt for D because it is easier to maintain (less special cases, less complexity, internally we could get rid of `assert_unique_multiindex_level_names` after dropping multi-index virtual variables) and also because an error is raised when there's actually an issue, e.g., we could do `stack` and never plan to do `unstack` later so in that case multi-index level vs. dimension name conflict is not an issue?

I was thinking about this kind of behavior (even though reverting previous changes is not ideal):

```python
ds = xr.Dataset(coords={'dim0': ['a', 'b'], 'dim1': [0, 1]})
ds = ds.stack(dim_stacked=['dim0', 'dim1'])

# This works: dim0 is not a dimension in b
ds['c'] = (('dim0',), [10, 11, 12, 13, 14, 15])

# raise a nice error message here: conflicting sizes for dimension 'dim0'
ds.unstack(dim_stacked)

# raise a nice error message here: conflicting sizes for dimension 'dim0'
ds.sel(dim1=0)
```

However, this may be confusing in the case of integer-based vs. label based indexing:

```python
# label-based selection along `dim_stacked` dimension (length=4)
ds.sel(dim0='a')

# integer-based selection along `dim0` dimension (length=6)
ds.isel(dim0=0)
```

So a more general rule like option C is not that silly after all?

If a dimension name matches the name of a coordinate:

- Ok if this coordinate is a ""dimension"" coordinate (coordinate name == dimension name)
- (maybe ok if this this coordinate is not indexed?) 
- Error otherwise","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,979316661
https://github.com/pydata/xarray/issues/5738#issuecomment-906159715,https://api.github.com/repos/pydata/xarray/issues/5738,906159715,IC_kwDOAMm_X842AuZj,4160723,2021-08-26T07:21:07Z,2021-08-26T07:21:07Z,MEMBER,@fujiisoup @shoyer @aseyboldt,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,979316661