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/4826#issuecomment-766973931,https://api.github.com/repos/pydata/xarray/issues/4826,766973931,MDEyOklzc3VlQ29tbWVudDc2Njk3MzkzMQ==,463809,2021-01-25T17:19:19Z,2021-01-25T17:19:19Z,CONTRIBUTOR,"Tagging a few maintainers: @dcherian @shoyer.

Sorry to tag you directly, hope that's ok. I think I've found the issue here and would like to provide a PR to fix, but need some input on what you think would be best.

To summarize, the current behavior leading to the bug is:

1. When a `bool` dtype is initially written, the `maybe_encode_bool` function us used to convert it the bool to a `i1` with a `vars.attr` that says it is actually a bool. It would appear from #2937 that it ends up an `i8` somehow anyway. https://github.com/pydata/xarray/blob/cc53a77ff0c8aaf8686f0b0bd7f75985b74e2054/xarray/conventions.py#L119
2. When this is loaded the first time, the `i8` is correctly identified as actually being a bool using the attributes. https://github.com/pydata/xarray/blob/cc53a77ff0c8aaf8686f0b0bd7f75985b74e2054/xarray/conventions.py#L352
3. However, 2 lines above that, there is a `encoding.setdefault(""dtype"", original_dtype)` so this Variable object now has `.encoding[""dtype""]` which is `i8`.
4. When I try to save this again, it tries `maybe_encode_bool` from step 1 again, but this time the function is bypassed because of step 3 above.
5. The dataset I write from step 4 now does not have the attribute identifying it as a bool, and so it's an `i8` when I load it back.

I can think of a few fixes:
- Drop the `.encoding` dict on load for bools. Presumably these `.encodings` are kept such that datasets attempts to preserve the compressor, chunk size, etc. of its source. However, given that `.encoding` seems to be dropped when I eg. do a `.astype(""bool"")` maybe this is OK for bools.
- Set `var.attrs[""dtype""] = np.dtype(""bool"")` on load. This would preserve what we'd get out of `maybe_encode_bool`. The challenge with this is that `.attrs` are not always preserved?
- Change `maybe_encode_bool` to not ignore when `.encoding[""dtype""]` exists. I suppose there would be a need to check that the compressor is still compatible, etc?

As a local fix while we consider these options, can you confirm that, as the docs state, the `.encoding` is only used for *serializing* and not *deserializing* arrays, and therefore if I drop the `.encoding` on my `DataArrays` as a temporary fix I wouldn't break anything (if I am ok with xarray not preserving my compressors, etc).","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,789410367
https://github.com/pydata/xarray/issues/4826#issuecomment-765747736,https://api.github.com/repos/pydata/xarray/issues/4826,765747736,MDEyOklzc3VlQ29tbWVudDc2NTc0NzczNg==,463809,2021-01-22T23:37:47Z,2021-01-22T23:38:22Z,CONTRIBUTOR,"OK here's the other side of the problem. The original dtype (which is i8) is set in the encoding:

https://github.com/pydata/xarray/blob/v0.16.2/xarray/conventions.py#L350","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,789410367
https://github.com/pydata/xarray/issues/4826#issuecomment-765741719,https://api.github.com/repos/pydata/xarray/issues/4826,765741719,MDEyOklzc3VlQ29tbWVudDc2NTc0MTcxOQ==,463809,2021-01-22T23:27:57Z,2021-01-22T23:27:57Z,CONTRIBUTOR,"Apparently my proposed fix broke a bunch of other things, eg. some writing of timedeltas with units and such.

Deleting the ""dtype"" key in the `.encoding` of the boolean variable also seems to do the trick. The issue is that bools are not encoded correctly if the `.encoding` field already has a `dtype`:

https://github.com/pydata/xarray/blob/v0.16.2/xarray/conventions.py#L119","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,789410367