# `Cheer.MixTask`
[🔗](https://github.com/joshrotenberg/cheer/blob/v0.2.1/lib/cheer/mix_task.ex#L1)

Build a Mix task from a Cheer command.

`use Cheer.MixTask` combines `use Mix.Task` and `use Cheer.Command` and
generates the Mix `run/1` entry point. That entry point dispatches argv through
the command with `Cheer.run/3`, using `mix <task>` as the program name in help
and usage output, and translates a usage failure into `exit({:shutdown, 2})`,
the Mix idiom for a nonzero exit.

Declare the command with the usual DSL and implement the leaf `run/2`:

    defmodule Mix.Tasks.Greet do
      use Cheer.MixTask

      command "greet" do
        about "Greet someone"
        argument :name, type: :string, required: true
        option :loud, type: :boolean, short: :l
      end

      @impl Cheer.Command
      def run(%{name: name} = args, _raw) do
        greeting = "Hello, #{name}!"
        greeting = if args[:loud], do: String.upcase(greeting), else: greeting
        Mix.shell().info(greeting)
      end
    end

Then `mix greet world --loud` parses, validates, and renders help exactly like
a standalone CLI.

`@shortdoc` defaults to the command's `about` text when it is not set
explicitly, so the task lists itself in `mix help`. Override `run/1` if the
task needs to do its own setup (such as `Mix.Task.run("app.start")`) before
dispatching.

Do not use `Cheer.main/3` in a Mix task: it calls `System.halt`, which
hard-kills the VM and skips Mix's cleanup. This helper uses `Cheer.run/3` and
the `exit` idiom instead.

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*Consult [api-reference.md](api-reference.md) for complete listing*