Cannot use function in custom mix task defined in same app

stevensonmt

I have an app with the following structure:

mix.exs
lib
  |_my_app.ex
  |_mix/tasks/my_mix_task.ex

The file lib/my_app.ex defines a module MyApp with a function load. The mix/tasks/my_mix_task.ex includes

defmodule Mix.Tasks.MyApp.MyTask do 
  use Mix.Task
 
 def run(_) do 
   Mix.Task.run("app.start")
    # IO stuff
   MyApp.load()
 end
end

When I run mix my_app.my_task the call to MyApp.load() gives

UndefinedFunctionError … (module MyApp is not available)

unless I run it from the root directory of my_app, in which case I get

(UndefinedFunctionError) function Hex.Mix.overridden_deps/1 is undefined (module Hex.Mix is not available)

I’ve run mix archive.build and mix archive.install to make it available globally.

Any ideas?

13 comments

#mix-tasks

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2023-11-26 16:53:05 UTC

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dimitarvp

What are your compilation paths? (In mix.exs)

Post #1

stevensonmt

It’s not specified in mix.exs. I believe it defaults to _build. FWIW, in my_app/_build/dev/lib/my_app/ebin/my_app.app I see:

{application, my_app, [
  {optional_applications, []}, 
  {applications, [kernel,stdllib,elixir,logger,my_dependency]},
  {description, "my_app"},
  {modules, ['Elixir.MyApp', 'Elixir.Mix.Tasks.MyApp.MyTask']}
  {registered, []},
  {vsn, "0.1.0"}
  ]
}

(some formatting changed to make it more readable)
– BTW updated OP with some additional error info when run from same directory it is defined in.

mix archive lists the my_app archive in the same path as things like credo, hex, and phx_new. And mix local lists the my_app.my_task along with the tasks defined by those other archives.

Post #2

dimitarvp

Ah no, I meant the elixirc_paths in your mix.exs’ project function.

Post #3

stevensonmt

elixirc_paths is not defined.

Post #4

100phlecs

~~I would guess the MyApp in the error above is referring to the module Mix.Tasks.MyApp, you need to define that first.~~ Elixir would print out the full module path, so this is wrong.

To also prevent confusion, I would recommend doing an abbreviation of some sort–this also adds the convenience of making it easier to type in the terminal, e.g. mix phx.gen.new vs mix phoenix.generate.new

edit: I tested this locally and it seems to work fine, so the above seems to be wrong. I just suspected some sort of module shadowing was taking place

Post #5

dimitarvp

Is Elixier a copy-paste mistake?

Post #6

stevensonmt

Oops, yeah

Post #7

stevensonmt

I’m not sure how to explain it but the error is still an undefined function error … module not available, but now it’s not the MyApp module but the dependency that MyApp.load uses. I just don’t understand how that dependency is not compiled and included when building the archive.

Post #8