If you need to change the source code of a dependency, I would copy the source code to another directory or git repo that you manage, edit the source code there, and then point the mix.exs deps entry to that new source location.

I think trying to edit it in the deps directory directly with a mix task is going to be swimming upstream from how it’s designed to be used.

I like to make my mix tasks double up as escripts for this purpose:

# lib/mix/tasks/secrets/mix.exs
defmodule Bonfire.Secrets do
  use Mix.Project

  def project do
    [
      app: :secrets,
      version: "0.1.0-alpha.1",
      elixir: "~> 1.11",
      escript: [main_module: Mix.Tasks.Bonfire.Secrets]
    ]
  end
end

# lib/mix/tasks/secrets/lib/secrets.ex
defmodule Mix.Tasks.Bonfire.Secrets do
  @shortdoc "Generates some secrets"

  @moduledoc """
  Generates random secrets and prints to the terminal.
  > mix bonfire.secrets [length]

  Can also compile/run it as an escript (without having to first compile the app):
  > cd lib/mix/tasks/secrets && mix escript.build && ./secrets [length]
  """
  use Mix.Task

  # for running as escript
  def main(args) do
    run(args)
  end

  @doc false
  def run([]), do: run(["64"])

  def run([int]),
    do: int |> parse!() |> random_string() |> Kernel.<>("\r\n") |> IO.puts()

  def run([int, iterate]), do: for(_ <- 1..parse!(iterate), do: run([int]))
  def run(args), do: nil

  defp parse!(int) do
    case Integer.parse(int) do
      {int, ""} -> int
      _ -> 64
    end
  end

  defp random_string(length) when length > 31 do
    :crypto.strong_rand_bytes(length)
    |> Base.encode64()
    |> binary_part(0, length)
  end
end

thanks, It’s useful