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/3091#issuecomment-510883034,https://api.github.com/repos/pydata/xarray/issues/3091,510883034,MDEyOklzc3VlQ29tbWVudDUxMDg4MzAzNA==,35968931,2019-07-12T13:18:34Z,2019-07-12T13:18:34Z,MEMBER,"Okay have a look at PR #3101.

It will now issue a function-specific warning depending on if you enter from `open_mfdataset` or `auto_combine`, e.g.

```python
""""""In xarray version 0.13 the default behaviour of `open_mfdataset`
will change. To retain the existing behavior, pass
combine='nested'. To use future default behavior, pass
combine='by_coords'. See http://xarray.pydata.org/en/stable/combining.html#combining-multi""""""
```

It links to [this page](http://xarray.pydata.org/en/stable/combining.html#combining-multi) of the docs. This is controlled by a hidden `from_openmfds` kwarg.

Then it issues the same set of warnings as before, whose exact form depends on the structure of the users input.

This could be improved further, but I think this should already be much clearer than before.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,466444738
https://github.com/pydata/xarray/issues/3091#issuecomment-510565507,https://api.github.com/repos/pydata/xarray/issues/3091,510565507,MDEyOklzc3VlQ29tbWVudDUxMDU2NTUwNw==,5635139,2019-07-11T16:48:17Z,2019-07-11T16:48:17Z,MEMBER,"I think that would be OK. 
Another option - more work but better - is to raise a single warning in `open_mfdataset` and suppress downstream warnings (we have a `suppress` contextmanager IIRC)

I'd generally weigh towards _less_ tax on people making changes, even if the user experience is a bit worse temporarily. So in this case I would vote to do whatever you're happy to do quickly @TomNicholas ","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,466444738
https://github.com/pydata/xarray/issues/3091#issuecomment-510558970,https://api.github.com/repos/pydata/xarray/issues/3091,510558970,MDEyOklzc3VlQ29tbWVudDUxMDU1ODk3MA==,35968931,2019-07-11T16:30:12Z,2019-07-11T16:30:12Z,MEMBER,"Okay fair points.

From an implementation point of view it makes sense to raise one warning just saying that function will be deprecated/have deprecated behaviour, then immediately raise further warnings with details as to what to do. (Otherwise you'll have to start secretly passing partial warning message strings into auto_combine, which is possible but seems clunky.) If I do that so it specifically refers to open_mfdataset in the first warning, then gives a (better) generic explanation in the second, do you think that would be sufficient? ","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,466444738
https://github.com/pydata/xarray/issues/3091#issuecomment-510555912,https://api.github.com/repos/pydata/xarray/issues/3091,510555912,MDEyOklzc3VlQ29tbWVudDUxMDU1NTkxMg==,5635139,2019-07-11T16:22:27Z,2019-07-11T16:22:27Z,MEMBER,"I don't use the function but so as an outsider: all the information is there, but it took me a few reads through to understand it. Depending on how widely used this is, I think something like this would be clearer (h/t to similar pandas' warnings):

> The default behavior of `open_mfdataset` will change in xarray [0.14] for datasets with global dimension coordinates: [datasets will be combined by their coords {maybe better explanation, maybe link}]
> To retain the existing behavior, pass `combine='nested'`. To use future default behavior, pass `combine='by_coords'`. ","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,466444738
https://github.com/pydata/xarray/issues/3091#issuecomment-510554824,https://api.github.com/repos/pydata/xarray/issues/3091,510554824,MDEyOklzc3VlQ29tbWVudDUxMDU1NDgyNA==,2448579,2019-07-11T16:19:33Z,2019-07-11T16:19:33Z,MEMBER,When calling `open_mfdataset` it's not clear why I'm getting a warning about `auto_combine` (as a user). The second warning seems OK.,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,466444738
https://github.com/pydata/xarray/issues/3091#issuecomment-510535887,https://api.github.com/repos/pydata/xarray/issues/3091,510535887,MDEyOklzc3VlQ29tbWVudDUxMDUzNTg4Nw==,35968931,2019-07-11T15:31:46Z,2019-07-11T15:32:05Z,MEMBER,"> I don't think we should be issuing this warning when using open_mfdataset with default kwargs

Why? Do you feel it's not clear enough? The warning is to indicate that the current behaviour of `open_mfdataset` will change slightly, and to not be caught by surprise then a `combine` argument should now be supplied. 

To understand why a deprecation cycle would be required read from [here](https://github.com/pydata/xarray/pull/2616#discussion_r254344467) (but it is long and confusing and the function names change so happy to explain the logic again if you want).","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,466444738