Mix compiler tracer for detecting unused public functions.

def deps do
  [
    {:mix_unused, "~> 0.3.0"}
  ]
end

The docs can be found at https://hexdocs.pm/mix_unused.

After installation you need to add :unused as a compiler to the list of Mix compilers:

defmodule MySystem.MixProject do
  use Mix.Project

  def project do
    [
      compilers: [:unused] ++ Mix.compilers(),
      # In case of Phoenix projects you need to add it to the list
      # compilers: [:unused, :phoenix, :gettext] ++ Mix.compilers()
      # ...
    ]
  end

  # ...
end

This isn't perfect solution and this will not find dynamic calls in form of:

apply(mod, func, args)

So this mean that, for example, if you have custom child_spec/1 definition then mix unused can return such function as unused even when you are using that indirectly in your supervisor.

You can define used functions by adding mfa in unused: [ignored: [⋯]] in your project configuration:

def project do
  [
    # ⋯
    unused: [
      ignore: [
        {MyApp.Foo, :child_spec, 1}
      ]
    ],
    # ⋯
  ]
end

See LICENSE.