At Shopify, we do a similar thing using a tool we wrote called Shadowenv[1], which evaluates little programs to manipulate the environment on directory entry/ex

At Shopify, we do a similar thing using a tool we wrote called Shadowenv[1], which evaluates little programs to manipulate the environment on directory entry/exit. It's a lot like direnv, but it can't do anything that makes it slow, and is guaranteed to run in at most 100ms (though it typically only takes a few) When I set `ruby: 2.6.8` in my `dev.yml` file, for example, I get this Shadowenv program written out to `.shadowenv.d/550_dev_ruby.lisp`: (provide "ruby" "2.6.8") (when-let ((ruby-root (env/get "RUBY_ROOT"))) (env/remove-from-pathlist "PATH" (path-concat ruby-root "bin")) (when-let ((gem-root (env/get "GEM_ROOT"))) (env/remove-from-pathlist "PATH" (path-concat gem-root "bin"))) (when-let ((gem-home (env/get "GEM_HOME"))) (env/remove-from-pathlist "PATH" (path-concat gem-home "bin")))) (env/set "BUNDLE_PATH" ()) (env/set "GEM_PATH" ()) (env/set "GEM_HOME" ()) (env/set "RUBYOPT" ()) (env/set "RUBYLIB" ()) (env/set "RUBY_ROOT" "/opt/rubies/2.6.8") (env/prepend-to-pathlist "PATH" "/opt/rubies/2.6.8/bin") (env/set "RUBY_ENGINE" "ruby") (env/set "RUBY_VERSION" "2.6.8") (env/set "GEM_ROOT" "/opt/rubies/2.6.8/lib/ruby/gems/2.6.0") (when-let ((gem-root (env/get "GEM_ROOT"))) (env/prepend-to-pathlist "GEM_PATH" gem-root) (env/prepend-to-pathlist "PATH" (path-concat gem-root "bin"))) (let ((gem-home (path-concat (env/get "HOME") ".gem" (env/get "RUBY_ENGINE") (env/get "RUBY_VERSION")))) (do (env/set "GEM_HOME" gem-home) (env/prepend-to-pathlist "GEM_PATH" gem-home) (env/prepend-to-pathlist "PATH" (path-concat gem-home "bin")))) I really like this strategy. It's really nicely generalizable to any of these language runtimes that need to change on a per-project basis. [1]: https://shopify.github.io/shadowenv/ https://shopify.github.io/shadowenv/