Okay my pants migration is far along enough to finally say.. macro time (oddly enough I'm realizing that this is my favorite part of being a long term bazel user... tweaking the build for your specific build). I have apps that I run with gunicorn. I got this target to work

pex_binary(
  name="app",
  script="gunicorn",
  args=["foo.bar.baz:app"],
  dependencies=[
    ":bar",   <---- This is the //foo/bar:bar where baz.py lives
    ".build/requirements:reqs#gunicorn"
],
)

I'd like to present this interface in the build

gunicorn_pex_binary(
  name="app",
  wsgi_app = file:app (where file == pwd/baz.py)
)

Where app is of form

$(module_name):$(variable_name)

Under the hood this makes the pex_binary target where the file is added as a dependency to the pex_binary target. Is there a way I can construct this macro by getting the .. calling location? of the target? In bazel I'd accomplish this with

package_name

and minimal starlark.

build_file_dir()

returns a

pathlib.PurePath

of the

BUILD

file's dir

Can I throw errors if something is invalid? Like wsgi_app doesn’t end with

.py

I don't remember. Try it and find out

you should be able to throw errors, I believe…