@tacaswell, I directly edited a change to this. Hope that was OK.

I approved this, but you could self-merge on my changes to get the test to work, or someone else could merge; I don't think I should merge since I last edited...

Thanks @jklymak !

In general assume you can push non-controversial stuff to any of my branches.

@anntzer had some questions about this in #14356 . I think that keeping checking until we find an un-masked element is the correct behavior which seems safer than assuming that a fill value will have the right units.

Yeah, though it is kind of wasteful for a long masked-out array. We still should sit down an write a specification for what units are and how they can be packed, because I'm not sure how we would get in the situation where a masked out element would have different units than the unmasked elements.

Also what happens if the whole array is masked? I'm not sure this will ever return anything?

It will have the same behavior as passing an empty list (which is to return None which may or may not be what we want it to do, but at least it is consistent?)

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

$ git checkout v3.1.x
$ git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

$ git cherry-pick -m1 177f9df5d2292369f3ce0544be1b3952e61c2f47

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

$ git commit -am 'Backport PR #14429: FIX: if the first elements of an array are masked keep checking'

4. Push to a named branch :

git push YOURFORK v3.1.x:auto-backport-of-pr-14429-on-v3.1.x

5. Create a PR against branch v3.1.x, I would have named this PR:

"Backport PR #14429 on branch v3.1.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to suggest an improvement.