kernel: Add possibility to disable prompt redrawing

When stdout is used as both a terminal and as the main logging
mechanism, redrawing the prompt will cause a lot of ANSI characters
to be printed to the log when the prompt is redrawn. So we add this
options for systems that have a hard time migrating away. It is
only available in Erlang/OTP 26 as a temporary measure as in the long
run no system should be using stdout as a logging mechanism and
terminal at the same time.

lib/kernel/src/group.erl

@@ -818,9 +818,14 @@ more_data(What, Cont0, Drv, Shell, Ls, Encoding) ->
             get_line1(edlin:edit_line(eof, Cont0), Drv, Shell, Ls, Encoding);
         {io_request,From,ReplyAs,Req} when is_pid(From) ->
             {more_chars,Cont,_More} = edlin:edit_line([], Cont0),
-            send_drv_reqs(Drv, edlin:erase_line()),
-            io_request(Req, From, ReplyAs, Drv, Shell, []), %WRONG!!!
-            send_drv_reqs(Drv, edlin:redraw_line(Cont)),
+            case application:get_env(stdlib, shell_redraw_prompt_on_output, true) of
+                true ->
+                    send_drv_reqs(Drv, edlin:erase_line()),
+                    io_request(Req, From, ReplyAs, Drv, Shell, []),
+                    send_drv_reqs(Drv, edlin:redraw_line(Cont));
+                false ->
+                    io_request(Req, From, ReplyAs, Drv, Shell, [])
+            end,
             get_line1({more_chars,Cont,[]}, Drv, Shell, Ls, Encoding);
         {reply,{From,ReplyAs},Reply} ->
             %% We take care of replies from puts here as well

lib/kernel/src/prim_tty.erl

@@ -137,6 +137,7 @@
                 reader :: {pid(), reference()} | undefined,
                 writer :: {pid(), reference()} | undefined,
                 options,
+                redraw_prompt_on_output = true,
                 unicode = true :: boolean(),
                 lines_before = [],   %% All lines before the current line in reverse order
                 lines_after = [],    %% All lines after the current line.
@@ -236,8 +237,11 @@ init(UserOptions) when is_map(UserOptions) ->
                      IOEncoding =:= unicode -> true;
                      true -> UnicodeSupported
                   end,
+    RedrawPrompt = application:get_env(stdlib, shell_redraw_prompt_on_output, true),
     {ok, ANSI_RE_MP} = re:compile(?ANSI_REGEXP, [unicode]),
-    init_term(#state{ tty = TTY, unicode = UnicodeMode, options = Options, ansi_regexp = ANSI_RE_MP }).
+    init_term(#state{ tty = TTY, unicode = UnicodeMode, options = Options,
+                      ansi_regexp = ANSI_RE_MP,
+                      redraw_prompt_on_output = RedrawPrompt }).
 init_term(State = #state{ tty = TTY, options = Options }) ->
     TTYState =
         case maps:get(tty, Options) of
@@ -631,15 +635,19 @@ handle_request(State, {expand_with_trim, Binary}) ->
     handle_request(State, 
                    {expand, iolist_to_binary(["\r\n",string:trim(Binary, both)])});
 %% putc prints Binary and overwrites any existing characters
-handle_request(State = #state{ unicode = U }, {putc, Binary}) ->
+handle_request(State = #state{ redraw_prompt_on_output = RedrawOnOutput,
+                               unicode = U }, {putc, Binary}) ->
     %% Todo should handle invalid unicode?
     %% print above the prompt if we have a prompt.
     %% otherwise print on the current line.
-    case {State#state.lines_before,{State#state.buffer_before, State#state.buffer_after}, State#state.lines_after} of
-        {[],{[],[]},[]} ->
+    if State#state.lines_before =:= [] andalso
+       State#state.buffer_before =:= [] andalso
+       State#state.buffer_after =:= [] andalso
+       State#state.lines_after =:= [];
+       not RedrawOnOutput ->
             {PutBuffer, _} = insert_buf(State, Binary),
             {[encode(PutBuffer, U)], State};
-        _ ->
+       true ->
             {Delete, DeletedState} = handle_request(State, delete_line),
             {PutBuffer, _} = insert_buf(DeletedState, Binary),
             {Redraw, _} = handle_request(State, redraw_prompt_pre_deleted),

lib/kernel/test/interactive_shell_SUITE.erl

@@ -59,6 +59,7 @@
          shell_expand_location_below/1,
          shell_update_window_unicode_wrap/1,
          shell_receive_standard_out/1,
+         shell_receive_user_output/1,
          shell_standard_error_nlcr/1, shell_clear/1,
          remsh_basic/1, remsh_error/1, remsh_longnames/1, remsh_no_epmd/1,
          remsh_expand_compatibility_25/1, remsh_expand_compatibility_later_version/1,
@@ -136,6 +137,7 @@ groups() ->
        shell_update_window, shell_small_window_multiline_navigation, shell_huge_input,
        shell_support_ansi_input,
        shell_receive_standard_out,
+       shell_receive_user_output,
        shell_standard_error_nlcr,
        shell_expand_location_above,
        shell_expand_location_below,
@@ -987,6 +989,40 @@ shell_receive_standard_out(Config) ->
         ok
     after
         stop_tty(Term)
+    end,
+    Term2 = start_tty([{args,["-stdlib","shell_redraw_prompt_on_output","false"]}|Config]),
+    try
+        send_tty(Term2,"my_fun(5) -> ok; my_fun(N) -> receive after 100 -> io:format(\"~p\\n\", [N]), my_fun(N+1) end.\n"),
+        send_tty(Term2,"spawn(shell_default, my_fun, [0]). ABC\n"),
+        timer:sleep(1000),
+        check_location(Term2, {0,-18}), %% Check that we are at the same location relative to the start.
+        check_content(Term2, "..0\\s+1\\s+2\\s+3\\s+4"),
+        ok
+    after
+        stop_tty(Term2)
+    end.
+shell_receive_user_output(Config) ->
+    Term = start_tty(Config),
+    try
+        send_tty(Term,"my_fun(5) -> ok; my_fun(N) -> timer:sleep(100), io:format(user, \"~p\\n\", [N]), my_fun(N+1).\n"),
+        send_tty(Term, "spawn(shell_default, my_fun, [0]). ABC\n"),
+        timer:sleep(1000),
+        check_location(Term, {0, 0}), %% Check that we are at the same location relative to the start.
+        check_content(Term, "3\\s+4\\s+.+>\\sABC"),
+        ok
+    after
+        stop_tty(Term)
+    end,
+    Term2 = start_tty([{args,["-stdlib","shell_redraw_prompt_on_output","false"]}|Config]),
+    try
+        send_tty(Term2,"my_fun(5) -> ok; my_fun(N) -> timer:sleep(100), io:format(user, \"~p\\n\", [N]), my_fun(N+1).\n"),
+        send_tty(Term2,"spawn(shell_default, my_fun, [0]). ABC\n"),
+        timer:sleep(1000),
+        check_location(Term2, {0,-18}), %% Check that we are at the same location relative to the start.
+        check_content(Term2, "..0\\s+1\\s+2\\s+3\\s+4"),
+        ok
+    after
+        stop_tty(Term2)
     end.
 %% Test that the shell works when invalid utf-8 (aka latin1) is sent to it
 shell_invalid_unicode(Config) ->