Stencil build with Bazel

I’m trying to call stencil build with bazel. For this reasons I’ve made a skylark rule-wrapper, but main problem is that bazel requires explicit inputs and outputs.
So question is there any way to predict which files stencil build command will produce?

I’ve looked into compiler’s sources and not sure if it possible at all, because looks like summary gathered after file system commit here

Thanks for any info