The motivation for this design is that package environments should be
#15541: package environment files and the GHC API -------------------------------------+------------------------------------- Reporter: lspitzner | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.6.1 Component: GHC API | Version: 8.4.3 Resolution: | Keywords: package | environment Operating System: Unknown/Multiple | Architecture: Type of failure: Documentation | Unknown/Multiple bug | Test Case: Blocked By: | Blocking: Related Tickets: #15513 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by lspitzner): transparent to the user, giving tooling a means of configuring GHC for a project without further user intervention. I consider the whole feature to be a mistake, see [https://hexagoxel.de/postsforpublish/posts/2018-08-25-ghc-pkg-env- misfeature.html this summary post]. As a consequence, if I had to choose between the options you presented, I'd vote for the first (rip out this side-effect from `setSessionDynFlags`). Some further opinionated thoughts: - If you expose `getFoo` and `setFoo`, `getFoo >>= setFoo` **must behave as identity**, free of (side- / other) effects. No amount of API docs excuses a violation. - It is likely to surprise and generally inadvisable to have any actions exposed in an API depend on `CWD`, especially by default. - The actions in the API should all have a single, clearly defined purpose. In brittany we encountered exactly the same question when it came to user config handling in its API. Perhaps have a look at how the brittany API is designed when it comes to `Config` values: https://hackage.haskell.org/package/brittany-0.11.0.0/docs/Language- Haskell-Brittany.html. Note how `parsePrintModule` is explicit about its inputs, promises to be semantically pure, and that there are separate actions that explicitly handle the filesystem reading of config files. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15541#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler