Implement removal of configuration

lib/igniter.ex

@@ -504,21 +504,51 @@ defmodule Igniter do
   """
   @spec update_elixir_file(t(), Path.t(), zipper_updater()) :: Igniter.t()
   def update_elixir_file(igniter, path, func) do
-    if Rewrite.has_source?(igniter.rewrite, path) do
-      igniter
-      |> apply_func_with_zipper(path, func)
-      |> format(path)
-    else
-      if exists?(igniter, path) do
-        source = read_ex_source!(igniter, path)
-
-        %{igniter | rewrite: Rewrite.put!(igniter.rewrite, source)}
-        |> format(path)
+    case use_or_read_elixir_file(igniter, path) do
+      {:exists, igniter} ->
+        igniter
         |> apply_func_with_zipper(path, func)
         |> format(path)
-      else
+
+      {:missing, igniter} ->
         add_issue(igniter, "Required #{path} but it did not exist")
-      end
+    end
+  end
+
+  @doc """
+  Updates the source code of the given elixir file if it exists
+  """
+  @spec update_existing_elixir_file(t(), Path.t(), zipper_updater(), keyword) :: Igniter.t()
+  def update_existing_elixir_file(igniter, path, func, opts \\ []) do
+    required? = Keyword.get(opts, :required?, false)
+
+    case use_or_read_elixir_file(igniter, path) do
+      {:exists, igniter} ->
+        igniter
+        |> apply_func_with_zipper(path, func)
+        |> format(path)
+
+      {:missing, igniter} ->
+        if required? do
+          add_issue(igniter, "Required #{path} but it did not exist")
+        else
+          igniter
+        end
+    end
+  end
+
+  defp use_or_read_elixir_file(igniter, path) do
+    cond do
+      Rewrite.has_source?(igniter.rewrite, path) ->
+        {:exists, igniter}
+
+      exists?(igniter, path) ->
+        source = read_ex_source!(igniter, path)
+        igniter = %{igniter | rewrite: Rewrite.put!(igniter.rewrite, source)}
+        {:exists, format(igniter, path)}
+
+      true ->
+        {:missing, igniter}
     end
   end
 

lib/igniter/project/config.ex

@@ -97,16 +97,7 @@ defmodule Igniter.Project.Config do
       |> Igniter.include_or_create_file(config_file_path, file_contents)
       |> ensure_default_configs_exist(file_path)
       |> Igniter.update_elixir_file(config_file_path, fn zipper ->
-        case Zipper.find(zipper, fn
-               {:import, _, [Config]} ->
-                 true
-
-               {:import, _, [{:__aliases__, _, [:Config]}]} ->
-                 true
-
-               _ ->
-                 false
-             end) do
+        case find_config(zipper) do
           nil ->
             {:warning,
              bad_config_message(
@@ -272,16 +263,7 @@ defmodule Igniter.Project.Config do
     |> ensure_default_configs_exist(file_name)
     |> Igniter.include_or_create_file(file_path, file_contents)
     |> Igniter.update_elixir_file(file_path, fn zipper ->
-      case Zipper.find(zipper, fn
-             {:import, _, [Config]} ->
-               true
-
-             {:import, _, [{:__aliases__, _, [:Config]}]} ->
-               true
-
-             _ ->
-               false
-           end) do
+      case find_config(zipper) do
         nil ->
           {:warning, bad_config_message(app_name, file_path, config_path, value, opts)}
 
@@ -294,6 +276,31 @@ defmodule Igniter.Project.Config do
     end)
   end
 
+  def remove_configuration(igniter, file_name, app_name) do
+    file_path = config_file_path(igniter, file_name)
+
+    Igniter.update_existing_elixir_file(igniter, file_path, fn zipper ->
+      case find_config(zipper) do
+        nil ->
+          igniter
+
+        _ ->
+          case Igniter.Code.Function.move_to_function_call_in_current_scope(
+                 zipper,
+                 :config,
+                 [2, 3],
+                 &Igniter.Code.Function.argument_equals?(&1, 0, app_name)
+               ) do
+            :error ->
+              :error
+
+            {:ok, zipper} ->
+              Zipper.remove(zipper)
+          end
+      end
+    end)
+  end
+
   defp config_file_path(igniter, file_name) do
     case igniter |> Igniter.Project.Application.config_path() |> Path.split() do
       [path] -> [path]
@@ -734,4 +741,17 @@ defmodule Igniter.Project.Config do
   defp simple_atom(value) do
     is_atom(value) and Regex.match?(~r/^[a-z_][a-zA-Z0-9_?!]*$/, to_string(value))
   end
+
+  defp find_config(zipper) do
+    Zipper.find(zipper, fn
+      {:import, _, [Config]} ->
+        true
+
+      {:import, _, [{:__aliases__, _, [:Config]}]} ->
+        true
+
+      _ ->
+        false
+    end)
+  end
 end

test/igniter/project/config_test.exs

@@ -719,4 +719,26 @@ defmodule Igniter.Project.ConfigTest do
       """)
     end
   end
+
+  describe "remove_configuration/3" do
+    test "it does not create the config file if it does not exist" do
+      test_project()
+      |> Igniter.Project.Config.remove_configuration("fake.exs", :fake)
+      |> refute_creates("config/fake.exs")
+    end
+
+    test "it removes the applications configuration if it exists" do
+      test_project()
+      |> Igniter.create_new_file("config/fake.exs", """
+        import Config
+
+        config :fake, buz: [:blat]
+      """)
+      |> apply_igniter!()
+      |> Igniter.Project.Config.remove_configuration("fake.exs", :fake)
+      |> assert_has_patch("config/fake.exs", """
+      3 - |config :fake, buz: [:blat]
+      """)
+    end
+  end
 end