fix(js): read the format key only when it holds formatter options

lib/volt/js/format.ex

@@ -27,9 +27,14 @@ defmodule Volt.JS.Format do
   @discovery_keys ~w(root sources ignore)a
 
   def load_config do
-    case Application.get_env(:volt, :format) do
-      nil -> load_json_config()
-      opts when is_list(opts) -> Keyword.drop(opts, @discovery_keys)
+    opts = Application.get_env(:volt, :format)
+
+    # The bundler reads the same key, where the value is an atom such as :esm.
+    # Only a keyword list carries formatter options.
+    if Keyword.keyword?(opts) do
+      Keyword.drop(opts, @discovery_keys)
+    else
+      load_json_config()
     end
   end
 

lib/volt/js/helpers.ex

@@ -38,5 +38,11 @@ defmodule Volt.JS.Helpers do
   end
 
   defp discovery_config(nil), do: []
-  defp discovery_config(tool), do: Application.get_env(:volt, tool, [])
+
+  defp discovery_config(tool) do
+    config = Application.get_env(:volt, tool, [])
+
+    # The bundler reads :format as an atom, so it holds no discovery keys.
+    if Keyword.keyword?(config), do: config, else: []
+  end
 end

test/volt/js/format_test.exs

@@ -25,4 +25,10 @@ defmodule Volt.JS.FormatTest do
 
     assert Format.load_config() == [semi: false, print_width: 100]
   end
+
+  test "load_config/0 ignores a bundle format set on the same key" do
+    Application.put_env(:volt, :format, :esm)
+
+    assert Format.load_config() == Format.load_json_config()
+  end
 end

test/volt/js/helpers_test.exs

@@ -44,6 +44,19 @@ defmodule Volt.JS.HelpersTest do
     assert Helpers.discover_files(tool: :lint) == [Path.join(tmp_dir, "lint/source.ts")]
   end
 
+  test "a bundle format on the same key holds no discovery options", %{tmp_dir: tmp_dir} do
+    Application.put_env(:volt, :format, :esm)
+
+    Application.put_env(:volt, :lint,
+      root: tmp_dir,
+      sources: ["lint/**/*.ts"],
+      ignore: []
+    )
+
+    assert Helpers.discover_format_files() == []
+    assert Helpers.discover_files(tool: :lint) == [Path.join(tmp_dir, "lint/source.ts")]
+  end
+
   defp restore_env(key, nil), do: Application.delete_env(:volt, key)
   defp restore_env(key, value), do: Application.put_env(:volt, key, value)
 end