Is it possible to specify dependencies for an instrumenter?

[nojb]

Is it possible to specify dependencies for an instrumenter? For example, in Bisect, we previously recommended using (preprocessor_deps ...) to give the filename of the exclusions file, i.e.

(preprocess (pps bisect_ppx --exclusions bisect.exclude))
(preprocessor_deps (file bisect.exclude))

Doing this now with

(instrumentation (backend bisect_ppx --exclusions bisect.exclude))
(preprocessor_deps (file bisect.exclude))

results in

5 |  (preprocessor_deps (file bisect.exclude))
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: This preprocessor_deps field will be ignored because no preprocessor
that might use them is configured.

Originally posted by @aantron in #3932 (comment)

[nojb]

This is not currently supported; since instrumentations could in the future be specified by other means than ppx preprocessors, I guess we would like a dedicated field, eg

(instrumentation
 (backend bisect_ppx --exclusions bisect.exclude)
 (deps bisect.exclude))

I haven't looked to the details, but this looks reasonable to me. cc @jeremiedimino

[ghost]

Me too. A deps field in the instrumentation one also look more natural to me than a preprocessor_deps field on the side of an instrumentation one. It makes the intent clearer.

[aantron]

Bisect still needs this. It's not practical to use Bisect with the new integration with complicated projects that need files excluded, because exclusion files cannot be found by Bisect when they are not copied into the build directory.

[nojb]

Bisect still needs this. It's not practical to use Bisect with the new integration with complicated projects that need files excluded, because exclusion files cannot be found by Bisect when they are not copied into the build directory.

Ack. Sorry, this slipped through the cracks. I will try to get around to it soon.