mix_man.ex

defmodule Mix.Tasks.Man do
  @moduledoc """
  Print documentation for given Elixir term.
  """

  @shortdoc "Show manual for term"

  use Mix.Task

  require IEx.Helpers

  @impl Mix.Task
  def run([]), do: Mix.shell().error("What manual you want?")

  def run([string]) do
    function =
      if string =~ ~r/^~[A-Za-z]$/ do
        "~" <> rest = string
        {Kernel, :"sigil_#{rest}"}
      else
        {:ok, code} = Code.string_to_quoted(string)
        ast = IEx.Introspection.decompose(code, __ENV__)
        {data, _} = Code.eval_quoted(ast)
        data
      end

    IEx.Introspection.h(function)
  end

  def run(["mix", command]) do
    Mix.Task.run("help", [command])
  end

  def run(args) do
    Mix.shell().error("Unknown term: #{join_args(args)}")
  end

  defp join_args(args) do
    Enum.map_join(args, " ", fn arg ->
      if arg =~ ~r/\s/ do
        inspect(arg)
      else
        arg
      end
    end)
  end
end