Would this cause a dependency cycle? Wondering since Xarray also makes use of Dask

Also do we do any other downstream dependency testing? If so, how do we handle that currently? If not, are there other downstream dependencies we would want to test and if so how should we manage that?

Would this cause a dependency cycle? Wondering since Xarray also makes use of Dask

xarray doesn't depend on dask, it's an optional import, so should be fine.

> conda search xarray --info
xarray 0.17.0 pyhd3eb1b0_0
--------------------------
file name   : xarray-0.17.0-pyhd3eb1b0_0.conda
name        : xarray
version     : 0.17.0
build       : pyhd3eb1b0_0
build number: 0
size        : 510 KB
license     : Apache-2.0
subdir      : noarch
url         : https://repo.anaconda.com/pkgs/main/noarch/xarray-0.17.0-pyhd3eb1b0_0.conda
md5         : 8702480113641ff680e55c3e70f78ea3
timestamp   : 2021-03-01 18:58:22 UTC
dependencies: 
  - numpy >=1.17
  - pandas >=0.25
  - python >=3.6
  - setuptools >=41.2

There are a few places in Dask where we have some Xarray-specific logic. For example

Our tests in tests_xarray.py just test that those code paths work as expected, so it seemed reasonable to me that we would run those tests in our CI since they are testing logic inside of Dask.

Yep agree it's worth testing. Just trying to figure out how best to handle downstream dependencies like Xarray

Gotcha. Today we've mostly been relying on downstream projects to do their own upstream testing (e.g. Xarray does this) and surface errors to us when changes to Dask cause downstream breakages. Overall, this setup has been benefitial -- for example this issue was reported last week and we were able to fix things before releasing.

I have less experience on how to do downstream testing well. I know Bokeh has a downstream CI build. We might want to ask them what their experience with that has been like.

I know numba uses this to check on downstream breakage: https://github.com/numba/texasbbq

*edit:
which, given that https://github.com/jrbourbeau/dask-integration-testing is linked in the README, I'm going to gather you're familiar with 😁

Well let's stick with this then to keep things simple for now. If we start collecting downstream test dependencies, we may want to split these out into their own CI job

Sorry I forgot to ask, did we only need to add the dependency for tests to run or are there other changes needed as well?

Just adding xarray causes the tests to be run 👍

Thanks all for reviewing!