fix: skip unknown deps in dot formatter

lib/igniter.ex

@@ -102,7 +102,13 @@ defmodule Igniter do
   @doc "Returns a new igniter"
   @spec new() :: t()
   def new do
-    %__MODULE__{rewrite: Rewrite.new(hooks: [Rewrite.Hook.DotFormatterUpdater])}
+    %__MODULE__{
+      rewrite:
+        Rewrite.new(
+          hooks: [Igniter.Rewrite.DotFormatterUpdater],
+          dot_formatter: Rewrite.DotFormatter.read!(ignore_unknown_deps: true)
+        )
+    }
     |> include_existing_elixir_file(".igniter.exs", required?: false)
     |> parse_igniter_config()
   end

lib/igniter/rewrite/dot_formatter_updater.ex

@@ -0,0 +1,33 @@
+defmodule Igniter.Rewrite.DotFormatterUpdater do
+  @moduledoc false
+
+  alias Rewrite.DotFormatter
+
+  @behaviour Rewrite.Hook
+
+  @formatter ".formatter.exs"
+
+  @impl true
+  def handle(:new, project) do
+    {:ok, %{project | dot_formatter: dot_formatter(project)}}
+  end
+
+  def handle({action, files}, project) when action in [:added, :updated] do
+    if dot_formatter?(files) do
+      {:ok, %{project | dot_formatter: dot_formatter(project)}}
+    else
+      :ok
+    end
+  end
+
+  defp dot_formatter(project) do
+    case DotFormatter.read(project, ignore_unknown_deps: true) do
+      {:ok, dot_formatter} -> dot_formatter
+      {:error, _error} -> DotFormatter.default()
+    end
+  end
+
+  defp dot_formatter?(@formatter), do: true
+  defp dot_formatter?(files) when is_list(files), do: Enum.member?(files, @formatter)
+  defp dot_formatter?(_files), do: false
+end

lib/igniter/test.ex

@@ -334,7 +334,7 @@ defmodule Igniter.Test do
       |> Map.put(
         :rewrite,
         Rewrite.new(
-          hooks: [Rewrite.Hook.DotFormatterUpdater],
+          hooks: [Igniter.Rewrite.DotFormatterUpdater],
           dot_formatter: igniter.rewrite.dot_formatter
         )
       )