Multi-line prompts in IEx (elixir-lang#14522)

Author: josevalim

lib/iex/lib/iex.ex

@@ -396,10 +396,8 @@ defmodule IEx do
   The supported options are:
 
     * `:auto_reload`
-    * `:alive_continuation_prompt`
     * `:alive_prompt`
     * `:colors`
-    * `:continuation_prompt`
     * `:default_prompt`
     * `:dot_iex`
     * `:history_size`
@@ -485,14 +483,8 @@ defmodule IEx do
 
     * `:default_prompt` - used when `Node.alive?/0` returns `false`
 
-    * `:continuation_prompt` - used when `Node.alive?/0` returns `false`
-      and more input is expected
-
     * `:alive_prompt` - used when `Node.alive?/0` returns `true`
 
-    * `:alive_continuation_prompt` - used when `Node.alive?/0` returns
-      `true` and more input is expected
-
   The following values in the prompt string will be replaced appropriately:
 
     * `%counter` - the index of the history
@@ -506,11 +498,17 @@ defmodule IEx do
   The parser is a "mfargs", which is a tuple with three elements:
   the module name, the function name, and extra arguments to
   be appended. The parser receives at least three arguments, the
-  current input as a string, the parsing options as a keyword list,
-  and the buffer as a string. It must return `{:ok, expr, buffer}`
-  or `{:incomplete, buffer}`.
+  current input as a charlist, the parsing options as a keyword list,
+  and the state. The initial state is an empty charlist. It must
+  return `{:ok, expr, state}` or `{:incomplete, state}`.
+
+  If the parser raises, the state is reset to an empty charlist.
 
-  If the parser raises, the buffer is reset to an empty string.
+  > In earlier Elixir versions, the parser would receive the input
+  > and the initial buffer as strings. However, this behaviour
+  > changed when Erlang/OTP introduced multiline editing. If you
+  > support earlier Elixir versions, you can normalize the inputs
+  > by calling `to_charlist/1`.
 
   ## `.iex`
 

lib/iex/lib/iex/app.ex

@@ -8,6 +8,10 @@ defmodule IEx.App do
   use Application
 
   def start(_type, _args) do
+    with :default <- Application.get_env(:stdlib, :shell_multiline_prompt, :default) do
+      Application.put_env(:stdlib, :shell_multiline_prompt, {IEx.Config, :prompt})
+    end
+
     children = [IEx.Config, IEx.Broker, IEx.Pry]
     Supervisor.start_link(children, strategy: :one_for_one, name: IEx.Supervisor)
   end

lib/iex/lib/iex/config.ex

@@ -13,15 +13,37 @@ defmodule IEx.Config do
     :inspect,
     :history_size,
     :default_prompt,
-    :continuation_prompt,
     :alive_prompt,
-    :alive_continuation_prompt,
     :width,
     :parser,
     :dot_iex,
     :auto_reload
   ]
 
+  # Generate a continuation prompt based on IEx prompt.
+  # This is set as global configuration on app start.
+  def prompt(prompt) do
+    case Enum.split_while(prompt, &(&1 != ?()) do
+      # It is not the default Elixir shell, so we use the default prompt
+      {_, []} ->
+        List.duplicate(?\s, max(0, prompt_width(prompt) - 3)) ++ ~c".. "
+
+      {left, right} ->
+        List.duplicate(?., prompt_width(left)) ++ right
+    end
+  end
+
+  # TODO: Remove this when we require Erlang/OTP 27+
+  @compile {:no_warn_undefined, :prim_tty}
+  @compile {:no_warn_undefined, :shell}
+  defp prompt_width(prompt) do
+    if function_exported?(:prim_tty, :npwcwidthstring, 1) do
+      :prim_tty.npwcwidthstring(prompt)
+    else
+      :shell.prompt_width(prompt)
+    end
+  end
+
   # Read API
 
   def configuration() do
@@ -53,20 +75,12 @@ defmodule IEx.Config do
     Application.fetch_env!(:iex, :default_prompt)
   end
 
-  def continuation_prompt() do
-    Application.get_env(:iex, :continuation_prompt, default_prompt())
-  end
-
   def alive_prompt() do
     Application.fetch_env!(:iex, :alive_prompt)
   end
 
-  def alive_continuation_prompt() do
-    Application.get_env(:iex, :alive_continuation_prompt, alive_prompt())
-  end
-
   def parser() do
-    Application.get_env(:iex, :parser, {IEx.Evaluator, :parse, []})
+    Application.fetch_env!(:iex, :parser)
   end
 
   def color(color) do
@@ -202,9 +216,7 @@ defmodule IEx.Config do
   defp validate_option({:inspect, new}) when is_list(new), do: :ok
   defp validate_option({:history_size, new}) when is_integer(new), do: :ok
   defp validate_option({:default_prompt, new}) when is_binary(new), do: :ok
-  defp validate_option({:continuation_prompt, new}) when is_binary(new), do: :ok
   defp validate_option({:alive_prompt, new}) when is_binary(new), do: :ok
-  defp validate_option({:alive_continuation_prompt, new}) when is_binary(new), do: :ok
   defp validate_option({:width, new}) when is_integer(new), do: :ok
   defp validate_option({:parser, tuple}) when tuple_size(tuple) == 3, do: :ok
   defp validate_option({:dot_iex, path}) when is_binary(path), do: :ok

lib/iex/lib/iex/evaluator.ex

@@ -55,26 +55,21 @@ defmodule IEx.Evaluator do
     end
   end
 
-  # If parsing fails, this might be a TokenMissingError which we treat in
-  # a special way (to allow for continuation of an expression on the next
-  # line in IEx).
-  #
-  # The first two clauses provide support for the break-trigger allowing to
-  # break out from a pending incomplete expression. See
-  # https://github.com/elixir-lang/elixir/issues/1089 for discussion.
-  @break_trigger "#iex:break\n"
+  @break_trigger ~c"#iex:break\n"
 
   @op_tokens [:or_op, :and_op, :comp_op, :rel_op, :arrow_op, :in_op] ++
                [:three_op, :concat_op, :mult_op]
 
-  @doc false
-  def parse(input, opts, parser_state)
+  @doc """
+  Default parsing implementation with support for pipes and #iex:break.
 
-  def parse(input, opts, ""), do: parse(input, opts, {"", :other})
+  If parsing fails, this might be a TokenMissingError which we treat in
+  a special way (to allow for continuation of an expression on the next
+  line in IEx).
+  """
+  def parse(input, opts, parser_state)
 
-  def parse(@break_trigger, _opts, {"", _} = parser_state) do
-    {:incomplete, parser_state}
-  end
+  def parse(input, opts, []), do: parse(input, opts, {[], :other})
 
   def parse(@break_trigger, opts, _parser_state) do
     :elixir_errors.parse_error(
@@ -87,14 +82,13 @@ defmodule IEx.Evaluator do
   end
 
   def parse(input, opts, {buffer, last_op}) do
-    input = buffer <> input
+    input = buffer ++ input
     file = Keyword.get(opts, :file, "nofile")
     line = Keyword.get(opts, :line, 1)
     column = Keyword.get(opts, :column, 1)
-    charlist = String.to_charlist(input)
 
     result =
-      with {:ok, tokens} <- :elixir.string_to_tokens(charlist, line, column, file, opts),
+      with {:ok, tokens} <- :elixir.string_to_tokens(input, line, column, file, opts),
            {:ok, adjusted_tokens} <- adjust_operator(tokens, line, column, file, opts, last_op),
            {:ok, forms} <- :elixir.tokens_to_quoted(adjusted_tokens, file, opts) do
         last_op =
@@ -108,7 +102,7 @@ defmodule IEx.Evaluator do
 
     case result do
       {:ok, forms, last_op} ->
-        {:ok, forms, {"", last_op}}
+        {:ok, forms, {[], last_op}}
 
       {:error, {_, _, ""}} ->
         {:incomplete, {input, last_op}}
@@ -119,7 +113,7 @@ defmodule IEx.Evaluator do
           file,
           error,
           token,
-          {charlist, line, column, 0}
+          {input, line, column, 0}
         )
     end
   end
@@ -189,9 +183,9 @@ defmodule IEx.Evaluator do
 
   defp loop(%{server: server, ref: ref} = state) do
     receive do
-      {:eval, ^server, code, counter, parser_state} ->
-        {status, parser_state, state} = parse_eval_inspect(code, counter, parser_state, state)
-        send(server, {:evaled, self(), status, parser_state})
+      {:eval, ^server, code, counter} ->
+        {status, state} = safe_eval_and_inspect(code, counter, state)
+        send(server, {:evaled, self(), status})
         loop(state)
 
       {:fields_from_env, ^server, ref, receiver, fields} ->
@@ -296,32 +290,19 @@ defmodule IEx.Evaluator do
     end
   end
 
-  defp parse_eval_inspect(code, counter, parser_state, state) do
-    try do
-      {parser_module, parser_fun, args} = IEx.Config.parser()
-      args = [code, [line: counter, file: "iex"], parser_state | args]
-      eval_and_inspect_parsed(apply(parser_module, parser_fun, args), counter, state)
-    catch
-      kind, error ->
-        print_error(kind, error, __STACKTRACE__)
-        {:error, "", state}
-    end
-  end
-
-  defp eval_and_inspect_parsed({:ok, forms, parser_state}, counter, state) do
+  defp safe_eval_and_inspect(forms, counter, state) do
     put_history(state)
     put_whereami(state)
-    state = eval_and_inspect(forms, counter, state)
-    {:ok, parser_state, state}
+    {:ok, eval_and_inspect(forms, counter, state)}
+  catch
+    kind, error ->
+      print_error(kind, error, __STACKTRACE__)
+      {:error, state}
   after
     Process.delete(:iex_history)
     Process.delete(:iex_whereami)
   end
 
-  defp eval_and_inspect_parsed({:incomplete, parser_state}, _counter, state) do
-    {:incomplete, parser_state, state}
-  end
-
   defp put_history(%{history: history}) do
     Process.put(:iex_history, history)
   end
@@ -410,12 +391,7 @@ defmodule IEx.Evaluator do
 
         _ ->
           banner = Exception.format_banner(kind, blamed, stacktrace)
-
-          if String.contains?(banner, IO.ANSI.reset()) do
-            [banner]
-          else
-            [IEx.color(:eval_error, banner)]
-          end
+          [IEx.color(:eval_error, banner)]
       end
 
     stackdata = Exception.format_stacktrace(prune_stacktrace(stacktrace))