mix_unused notifies Phoenix liveview functions, such as __phoenix_verify_routes__

[kubosuke]

hint: TestWeb.RedirectToController.__phoenix_verify_routes__/1 is unused
    lib/test_web/controllers/redirect_to_controller.ex:1

defmodule TestWeb.RedirectToController do
  use TestWeb, :controller

  def call(conn, to: to) do
    conn
    |> redirect(to: ~u"#{to}")
    |> halt()
  end
end

these Phoenix functions should be ignored

[hauleth]

The thing is that this library do not assume anything about source code. That is why at the beginning there is some configuration required to make everything not that noisy. Good default is to use {:_, ~r/__.*__/} in ignore list, to ignore all functions like that.

I am not sure if that should be enabled by default and if so, what should be the API to not include that option in the default filters.

There is example list of filters that I use in my own Phoenix project:

[
  ignore: [
    Langusta.Repo,
    LangustaWeb.Gettext,
    LangustaWeb.Endpoint,
    LangustaWeb.Router,
    LangustaWeb.Router.Helpers,
    {:_, ~r/^__.*__\??$/},
    {:_, :child_spec, 1},
    {:_, :start_link, 1},
    {~r/^LangustaWeb\.Views\./, :render, 1..2},
    {~r/^LangustaWeb\.Views\./, :template_not_found, 2},
    ~r/^LangustaWeb\..*Controller$/,
    ~r/^LangustaWeb\.Cldr/,
    # Ignore views
    fn _, meta -> meta.doc_meta[:view] end,
    # Ignore functions marked as compile-time functions
    fn _, meta -> meta.doc_meta[:compile] end,
    # Ignore unused code in test/support/
    fn _, meta -> meta.file =~ ~r|test/support/| end
  ]
]

It probably could be added to README to make it more discoverable, but for now I will close it unless there is some clever metric how to detect such functions.

Ideally Elixir would mark generated functions in compile metadata, that would allow me to filter these function automatically (or provide a helper to filter them out without much of user interaction.