Dynamically list modules OR How to convert from snake case to camel case for modules with all caps

justincjohnson · October 19, 2017, 1:40pm

I have a metaprogramming question.

I have some modules in my code base (of course). Some are normal camel case modules (e.g. Abc.Def.Ghi) and some have all caps (e.g. Jkl.Mno.PQR). I want to construct the module names dynamically from snake case strings. This can be done fine with Macro.camelize/1 for the normal camel case modules, but the all caps parts mess this up. To overcome this I was wondering if there is a way to dynamically lookup the available modules so I can find the match ignoring case and use that. Does anyone know if this is possible?

I was hoping Module.__info__/1 would accept a :modules atom to get its sub-modules but that isn’t an option, which makes sense.

Another thought I had was if perhaps I can somehow register these details during module compilation by hooking into the compilation system.

Any help is appreciated. Thanks.

justincjohnson · October 19, 2017, 1:55pm

I found what I need in Elixir’s IEx.Autocomplete module, so I’ve copied this into my codebase.

github.com

elixir-lang/elixir/blob/e95f564b7448ffdcfaf5124d74698232c3d02a0e/lib/iex/lib/iex/autocomplete.ex#L274


defp valid_alias_rest?(rest), do: valid_alias_piece?(rest)


## Helpers


defp usable_as_unquoted_module?(name) do
  # Conversion to atom is not a problem because
  # it is only called with existing modules names.
  Code.Identifier.classify(String.to_atom(name)) != :other
end


defp match_modules(hint, root) do
  get_modules(root)
  |> :lists.usort()
  |> Enum.drop_while(&(not String.starts_with?(&1, hint)))
  |> Enum.take_while(&String.starts_with?(&1, hint))
end


defp get_modules(true) do
  ["Elixir.Elixir"] ++ get_modules(false)
end