fix: vendor Path.relative_to to get 1.18.4 behavior

Author: zachdaniel

lib/igniter.ex

@@ -1510,8 +1510,8 @@ defmodule Igniter do
   def format(igniter, adding_paths, reevaluate_igniter_config? \\ true) do
     igniter =
       igniter
-      |> include_existing_elixir_file("config/config.exs", require?: false)
-      |> include_existing_elixir_file("config/#{Mix.env()}.exs", require?: false)
+      |> include_existing_elixir_file("config/config.exs")
+      |> include_existing_elixir_file("config/#{Mix.env()}.exs")
 
     if adding_paths &&
          Enum.any?(List.wrap(adding_paths), &(Path.basename(&1) == ".formatter.exs")) do
@@ -1706,7 +1706,13 @@ defmodule Igniter do
           source_handler.from_string(content, path: path)
           |> Map.put(:from, :file)
         else
-          raise "File #{path} not found in test files."
+          raise """
+          File #{path} not found in test files.
+
+          Available Files:
+
+          #{Enum.map_join(Map.keys(igniter.assigns[:test_files]), "\n", &"  * #{&1}")}
+          """
         end
       else
         source_handler.read!(path)
@@ -1985,8 +1991,8 @@ defmodule Igniter do
       :unavailable
   end
 
-  defp subdirectory?(path, base_path) do
-    case Path.relative_to(path, base_path) do
+  def subdirectory?(path, base_path) do
+    case relative_to(path, base_path) do
       # Same path, not a subdirectory
       ^base_path ->
         false
@@ -2001,4 +2007,72 @@ defmodule Igniter do
         end
     end
   end
+
+  defp relative_to(path, cwd, opts \\ []) when is_list(opts) do
+    os_type = :os.type() |> elem(0)
+    split_path = Path.split(path)
+    split_cwd = Path.split(cwd)
+    force = Keyword.get(opts, :force, false)
+
+    case {split_absolute?(split_path, os_type), split_absolute?(split_cwd, os_type)} do
+      {true, true} ->
+        split_path = expand_split(split_path)
+        split_cwd = expand_split(split_cwd)
+
+        case force do
+          true -> relative_to_forced(split_path, split_cwd, split_path)
+          false -> relative_to_unforced(split_path, split_cwd, split_path)
+        end
+
+      {false, false} ->
+        split_path = expand_relative(split_path, [], [])
+        split_cwd = expand_relative(split_cwd, [], [])
+        relative_to_forced(split_path, split_cwd, [])
+
+      {_, _} ->
+        Path.join(expand_relative(split_path, [], []))
+    end
+  end
+
+  defp relative_to_unforced(path, path, _original), do: "."
+
+  defp relative_to_unforced([h | t1], [h | t2], original),
+    do: relative_to_unforced(t1, t2, original)
+
+  defp relative_to_unforced([_ | _] = l1, [], _original), do: Path.join(l1)
+  defp relative_to_unforced(_, _, original), do: Path.join(original)
+
+  defp relative_to_forced(path, path, _original), do: "."
+  defp relative_to_forced(["."], _path, _original), do: "."
+  defp relative_to_forced(path, ["."], _original), do: Path.join(path)
+  defp relative_to_forced([h | t1], [h | t2], original), do: relative_to_forced(t1, t2, original)
+
+  # this should only happen if we have two paths on different drives on windows
+  defp relative_to_forced(original, _, original), do: Path.join(original)
+
+  defp relative_to_forced(l1, l2, _original) do
+    base = List.duplicate("..", length(l2))
+    Path.join(base ++ l1)
+  end
+
+  defp expand_relative([".." | t], [_ | acc], up), do: expand_relative(t, acc, up)
+  defp expand_relative([".." | t], acc, up), do: expand_relative(t, acc, [".." | up])
+  defp expand_relative(["." | t], acc, up), do: expand_relative(t, acc, up)
+  defp expand_relative([h | t], acc, up), do: expand_relative(t, [h | acc], up)
+  defp expand_relative([], [], []), do: ["."]
+  defp expand_relative([], acc, up), do: up ++ :lists.reverse(acc)
+
+  defp expand_split([head | tail]), do: expand_split(tail, [head])
+  defp expand_split([".." | t], [_, last | acc]), do: expand_split(t, [last | acc])
+  defp expand_split([".." | t], acc), do: expand_split(t, acc)
+  defp expand_split(["." | t], acc), do: expand_split(t, acc)
+  defp expand_split([h | t], acc), do: expand_split(t, [h | acc])
+  defp expand_split([], acc), do: :lists.reverse(acc)
+
+  defp split_absolute?(split, :win32), do: win32_split_absolute?(split)
+  defp split_absolute?(split, _), do: match?(["/" | _], split)
+
+  defp win32_split_absolute?(["//" | _]), do: true
+  defp win32_split_absolute?([<<_, ":/">> | _]), do: true
+  defp win32_split_absolute?(_), do: false
 end