unused_inputs_list and caching

[Konstantin]

Bazel action run has an attribute "unused_inputs_list" to trim action inputs to only those actually used. We put that attribute to the heavy use. Now Bazel caching comes into picture and we are not sure those two features are properly coordinated.

Action cache lookup key combines action input hashes plus something else (not important here). We are under impression that even though action uses "unused_inputs_list" its cache key is created from untrimmed list of inputs causing cache miss for the next build.

I wonder how to proof or disproof this assumption.

Any ideas?

Konstantin