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/pull/3598#issuecomment-562310739,https://api.github.com/repos/pydata/xarray/issues/3598,562310739,MDEyOklzc3VlQ29tbWVudDU2MjMxMDczOQ==,1312546,2019-12-05T20:47:02Z,2019-12-05T20:47:02Z,MEMBER,"Hopefully the new comments make sense. I'm struggling a bit to explain things since I don't fully understand them myself :)

> So it was a graph construction issue.

I *think* so. Dask doesn't actually validate arguments passed to HighLevelGraph. But I believe we assume that when all the values in `dependencies` are themselves keys of `layers`. We didn't have that before with things like

```
(Pdb) pp collections[0].dask.dependencies
{'all-84bc51ac43a9275b3662b0089710eab9': {'or_-64f95b81b2f8001b4c61f2023ac4c223'},
 ...
 'eq-abac622d95ce5055d3e7b7dea944ec37': {'lambda-e79de3edfa267f41111057d26471bce3-x',
                                         'ones-c4a83f4b990021618d55e0fa61a351d6'},
...
}
 ```

The `'lambda-e79de3edfa267f41111057d26471bce3-x'` wasn't a layer of the graph. It was previously nested under the single new layer we were creating `gname` or `lambda-e79de3edfa267f41111057d26471bce3` in this case.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,533555794