A simple experiment to see if we can fetch definitions (unfoldings) of the transitive closure of a module from within a GHC Plugin:
- plugin: the plugin, prints all definitions it has access to.
- examples: a package that uses this plugin.
- test-lib: a library used by "examples".
This stanza in the cabal.project file is the key bit:
package *
ghc-options: -fexpose-all-unfoldings
It re-compiles all the dependencies with the flag -fexpose-all-unfoldings which
allows us to fetch the definitions.
This doesn't work for GHC's core libraries; Cabal always uses their precompiled versions.
To try this, you can run cabal v2-build all > all_unfoldings.txt.
This compiles examples with the GHC plugin and writes its output to all_unfoldings.txt
in which you should see all definitions from the libraries
unordered-containers (a direct dependency of examples) and
hashable (a transitive dependency of examples).