@pbrisbin this PR is failing because stack-action detects a file with the name stack-nightly.yml and then calls stack with --resolver nightly. This ignores the contents of stack-nightly.yml file. Is this expected behavior? If so, why have any content in stack-nightly.yml at all?

stack-action code: https://github.com/freckle/stack-action/blob/2e37b29addb79880b5fdfd22b48aa8fc07745f61/src/stack-cli.ts#L44-L49

This ignores the contents of stack-nightly.yml file.

It's not ignoring the contents of stack-nightly.yaml, it's overriding the resolver. That's because resolver: nightly doesn't work -- you must use a concrete date. Therefore, we tend to put the date of the last time we've maintained the file, and then use --resolver nightly.

Is this expected behavior?

Yes, see above. The need for --resolver nightly is why stack-action does what it does.

If so, why have any content in stack-nightly.yml at all?

It's true that if resolver were the only thing in the file we could somehow make things work without it, but it's very rare you don't also need extra-deps or allower-new directives to get nightly compiling, which are not being ignored. Additionally, the presence of a file with this name is how stack-action knows what to do.

cc @pbrisbin can you take a look; I had to make changes so I can't merge my own changes.