Make shell compatible with OTP 26 (#12114)

Author: josevalim

lib/iex/lib/iex/broker.ex

@@ -10,27 +10,29 @@ defmodule IEx.Broker do
   ## Shell API
 
   @doc """
-  Finds the IEx server running inside `:user_drv`, on this node exclusively.
+  Finds the IEx server.
   """
   @spec shell :: shell()
+  # TODO: Use shell:whereis_shell() from Erlang/OTP 26+.
   def shell() do
-    # Locate top group leader when using the "new shell".
     if user = Process.whereis(:user) do
-      case :group.interfaces(user) do
-        # Old or no shell
-        [] ->
-          nil
-
-        # Get current group from user_drv
-        [user_drv: user_drv] ->
-          case :user_drv.interfaces(user_drv) do
-            [] -> nil
-            [current_group: group] -> :group.interfaces(group)[:shell]
-          end
+      if user_drv = get_from_dict(user, :user_drv) do
+        if group = get_from_dict(user_drv, :current_group) do
+          get_from_dict(group, :shell)
+        end
       end
     end
   end
 
+  defp get_from_dict(pid, key) do
+    with {:dictionary, dictionary} <- Process.info(pid, :dictionary),
+         {^key, value} <- List.keyfind(dictionary, key, 0) do
+      value
+    else
+      _ -> nil
+    end
+  end
+
   @doc """
   Finds the evaluator and server running inside `:user_drv`, on this node exclusively.
   """

lib/iex/lib/iex/cli.ex

@@ -50,22 +50,28 @@ defmodule IEx.CLI do
   a dumb terminal version is started instead.
   """
   def start do
-    if tty_works?() do
-      :user_drv.start([:"tty_sl -c -e", tty_args()])
-    else
-      if get_remsh(:init.get_plain_arguments()) do
-        IO.puts(
-          :stderr,
-          "warning: the --remsh option will be ignored because IEx is running on limited shell"
-        )
-      end
+    # TODO: We can remove the -user callback on Erlang/OTP 26+ in favor of eval
+    cond do
+      Code.ensure_loaded?(:prim_tty) ->
+        :user_drv.start(%{initial_shell: tty_args()})
+
+      tty_works?() ->
+        :user_drv.start([:"tty_sl -c -e", tty_args()])
+
+      true ->
+        if get_remsh(:init.get_plain_arguments()) do
+          IO.puts(
+            :stderr,
+            "warning: the --remsh option will be ignored because IEx is running on limited shell"
+          )
+        end
 
-      :user.start()
+        :user.start()
 
-      # IEx.Broker is capable of considering all groups under user_drv but
-      # when we use :user.start(), we need to explicitly register it instead.
-      # If we don't register, pry doesn't work.
-      IEx.start([register: true] ++ options(), {:elixir, :start_cli, []})
+        # IEx.Broker is capable of considering all groups under user_drv but
+        # when we use :user.start(), we need to explicitly register it instead.
+        # If we don't register, pry doesn't work.
+        IEx.start([register: true] ++ options(), {:elixir, :start_cli, []})
     end
   end