Add Regex.import/1 (#14910)

Author: sabiwara

lib/elixir/lib/regex.ex

@@ -102,8 +102,8 @@ defmodule Regex do
       (the previous `r` option is deprecated in favor of `U`)
 
     * `:export` (E) (since Elixir 1.19.3) - uses an exported pattern
-      which can be shared across nodes or through config, at the cost of a runtime
-      overhead every time to re-import it every time it is executed.
+      which can be shared across nodes or passed through config, at the cost of a runtime
+      overhead to re-import it every time it is executed.
       This modifier only has an effect starting on Erlang/OTP 28, and it is ignored
       on older versions (i.e. `~r/foo/E == ~r/foo/`). This is because patterns cannot
       and do not need to be exported in order to be shared in these versions.
@@ -275,6 +275,35 @@ defmodule Regex do
     regex
   end
 
+  @doc """
+  Imports a `regex` that has been exported, otherwise returns the `regex` unchanged.
+
+  This means it will lose the ability to be sent across nodes or passed through config,
+  but will be faster since it won't need to be imported on the fly every time it is executed.
+
+  Exported regexes only exist on OTP 28, so this has no effect on older versions.
+
+  ## Examples
+
+      Regex.import(~r/foo/E)
+      ~r/foo/
+
+      Regex.import(~r/foo/)
+      ~r/foo/
+
+  """
+  @doc since: "1.20.0"
+  @spec import(t) :: t
+  def import(%Regex{re_pattern: re_pattern} = regex) do
+    case re_pattern do
+      {:re_exported_pattern, _, _, _, _} ->
+        %{regex | re_pattern: :re.import(re_pattern), opts: regex.opts -- [:export]}
+
+      _ ->
+        regex
+    end
+  end
+
   @doc """
   Returns the version of the underlying Regex engine.
   """

lib/elixir/test/elixir/regex_test.exs

@@ -132,6 +132,18 @@ defmodule RegexTest do
     end
   end
 
+  test "import/1" do
+    # no-op for non-exported regexes
+    regex = ~r/foo/
+    assert Regex.import(regex) == regex
+
+    imported = Regex.import(~r/foo/E)
+
+    assert imported.opts == []
+    assert "foo" =~ imported
+    assert {:re_pattern, _, _, _, _} = imported.re_pattern
+  end
+
   test "opts/1" do
     assert Regex.opts(Regex.compile!("foo", "i")) == [:caseless]
     assert Regex.opts(Regex.compile!("foo", [:ucp])) == [:ucp]