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# Igniter

Igniter is a code generation and project patching framework.

For library authors, this is a tool kit for writing smarter generators that can semantically modify existing files.

For end-users, this means `mix igniter.install <package>`, which will _add it to your mix.exs automatically_ and then run that library's installer if it has one. Even when libraries don't have an installer, or use igniter, this behavior makes it useful to keep around.

## Limitations

Right now, all files that are touched are formatted in their entirety. This may be a deal breaker for some users. I believe that we can solve this without changing the fundemental design of the project, but it is not a high priority.

## Installation

Igniter can be added to an existing elixir project by adding it to your dependencies:

```elixir
{:igniter, "~> 0.1"}
```

You can also generate new projects with igniter preinstalled, and run installers in the same command.

First, install the archive:

```elixir
mix archive.install hex igniter_new
```

Then you can run `mix igniter.new`

```
mix igniter.new app_name --install ash
```

Or if you want to use a different project creator, specify the mix task name with the `--with` flag. Any arguments will be passed through to that task, with the exception of `--install` and `--example`.

```
mix igniter.new app_name --install ash --with phx.new --no-ecto
```

## Patterns

Mix tasks built with igniter are both individually callable, _and_ composable. This means that tasks can call each other, and also end users can create and customize their own generators composing existing tasks.

### Installers

Igniter will look for a task called `<your_package>.install` when the user runs `mix igniter.install <your_package>`, and will run it after installing and fetching dependencies.

### Generators/Patchers

These can be run like any other mix task, or composed together. For example, lets say that you wanted to have your own `Ash.Resource` generator, that starts with the default `mix ash.gen.resource` task, but then adds or modifies files:

```elixir
# in lib/mix/tasks/my_app.gen.resource.ex
defmodule Mix.Tasks.MyApp.Gen.Resource do
  use Igniter.Mix.Task

  def igniter(igniter, [resource | _] = argv) do
    resource = Igniter.Code.Module.parse(resource)
    my_special_thing = Module.concat([resource, SpecialThing])
    location = Igniter.Code.Module.proper_location(my_special_thing)

    igniter
    |> Igniter.compose_task("ash.gen.resource", argv)
    |> Igniter.create_new_elixir_file(location, """
    defmodule #{inspect(my_special_thing)} do
      # this is the special thing for #{inspect()}
    end
    """)
  end
end
```