fix(embed): handle stdio in server properly

Rename stdin/stdout in the server, so that RPC data won't get corrupted.
This also restores the use of stderr to write directly to the terminal.

8 files changed, 40 insertions, 11 deletions

diff --git a/src/nvim/channel.c b/src/nvim/channel.c
index f2e5a37b34..386ec832eb 100644
--- a/src/nvim/channel.c
+++ b/src/nvim/channel.c
@@ -377,6 +377,7 @@ Channel *channel_job_start(char **argv, CallbackReader on_stdout, CallbackReader
   } else {
     has_out = rpc || callback_reader_set(chan->on_data);
     has_err = callback_reader_set(chan->on_stderr);
+    proc->fwd_err = chan->on_stderr.fwd_err;
   }
 
   switch (stdin_mode) {
@@ -519,6 +520,13 @@ uint64_t channel_from_stdio(bool rpc, CallbackReader on_output, const char **err
     stdout_dup_fd = os_dup(STDOUT_FILENO);
     os_replace_stdout_and_stderr_to_conout();
   }
+#else
+  if (embedded_mode) {
+    stdin_dup_fd = dup(STDIN_FILENO);
+    stdout_dup_fd = dup(STDOUT_FILENO);
+    dup2(STDERR_FILENO, STDOUT_FILENO);
+    dup2(STDERR_FILENO, STDIN_FILENO);
+  }
 #endif
   rstream_init_fd(&main_loop, &channel->stream.stdio.in, stdin_dup_fd, 0);
   wstream_init_fd(&main_loop, &channel->stream.stdio.out, stdout_dup_fd, 0);
diff --git a/src/nvim/channel.h b/src/nvim/channel.h
index d7f32d8988..5743eaead5 100644
--- a/src/nvim/channel.h
+++ b/src/nvim/channel.h
@@ -66,6 +66,7 @@ typedef struct {
   garray_T buffer;
   bool eof;
   bool buffered;
+  bool fwd_err;
   const char *type;
 } CallbackReader;
 
@@ -73,6 +74,7 @@ typedef struct {
                                                 .self = NULL, \
                                                 .buffer = GA_EMPTY_INIT_VALUE, \
                                                 .buffered = false, \
+                                                .fwd_err = false, \
                                                 .type = NULL })
 static inline bool callback_reader_set(CallbackReader reader)
 {
diff --git a/src/nvim/event/libuv_process.c b/src/nvim/event/libuv_process.c
index 811d96ff93..10a09275d9 100644
--- a/src/nvim/event/libuv_process.c
+++ b/src/nvim/event/libuv_process.c
@@ -85,6 +85,9 @@ int libuv_process_spawn(LibuvProcess *uvproc)
     uvproc->uvstdio[2].flags = UV_CREATE_PIPE | UV_WRITABLE_PIPE;
     uvproc->uvstdio[2].data.stream = STRUCT_CAST(uv_stream_t,
                                                  &proc->err.uv.pipe);
+  } else if (proc->fwd_err) {
+    uvproc->uvstdio[2].flags = UV_INHERIT_FD;
+    uvproc->uvstdio[2].data.fd = STDERR_FILENO;
   }
 
   int status;
diff --git a/src/nvim/event/process.c b/src/nvim/event/process.c
index 2fa789ac9a..9dfd6f329a 100644
--- a/src/nvim/event/process.c
+++ b/src/nvim/event/process.c
@@ -43,6 +43,9 @@ static int exit_need_delay = 0;
 int process_spawn(Process *proc, bool in, bool out, bool err)
   FUNC_ATTR_NONNULL_ALL
 {
+  // forwarding stderr contradicts with processing it internally
+  assert(!(err && proc->fwd_err));
+
   if (in) {
     uv_pipe_init(&proc->loop->uv, &proc->in.uv.pipe, 0);
   } else {
diff --git a/src/nvim/event/process.h b/src/nvim/event/process.h
index 26e03ff4f3..e0057faffb 100644
--- a/src/nvim/event/process.h
+++ b/src/nvim/event/process.h
@@ -38,7 +38,7 @@ struct process {
   /// Exit handler. If set, user must call process_free().
   process_exit_cb cb;
   internal_process_cb internal_exit_cb, internal_close_cb;
-  bool closed, detach, overlapped;
+  bool closed, detach, overlapped, fwd_err;
   MultiQueue *events;
 };
 
@@ -62,7 +62,8 @@ static inline Process process_init(Loop *loop, ProcessType type, void *data)
     .closed = false,
     .internal_close_cb = NULL,
     .internal_exit_cb = NULL,
-    .detach = false
+    .detach = false,
+    .fwd_err = false,
   };
 }
 
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 9bb9eea4f6..953385836b 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -279,6 +279,15 @@ int main(int argc, char **argv)
   // argument list "global_alist".
   command_line_scan(&params);
 
+#ifndef MSWIN
+  int tty_fd = params.input_isatty
+    ? STDIN_FILENO
+    : (params.output_isatty
+       ? STDOUT_FILENO
+       : (params.err_isatty ? STDERR_FILENO : -1));
+  pty_process_save_termios(tty_fd);
+#endif
+
   nlua_init(argv, argc, params.lua_arg0);
   TIME_MSG("init lua interpreter");
 
@@ -1455,14 +1464,6 @@ static void check_and_set_isatty(mparm_T *paramp)
   stdout_isatty
     = paramp->output_isatty = os_isatty(STDOUT_FILENO);
   paramp->err_isatty = os_isatty(STDERR_FILENO);
-#ifndef MSWIN
-  int tty_fd = paramp->input_isatty
-    ? STDIN_FILENO
-    : (paramp->output_isatty
-       ? STDOUT_FILENO
-       : (paramp->err_isatty ? STDERR_FILENO : -1));
-  pty_process_save_termios(tty_fd);
-#endif
   TIME_MSG("window checked");
 }
 
diff --git a/src/nvim/os/pty_process_unix.c b/src/nvim/os/pty_process_unix.c
index 143f0b3900..cd2150a6a6 100644
--- a/src/nvim/os/pty_process_unix.c
+++ b/src/nvim/os/pty_process_unix.c
@@ -168,6 +168,14 @@ static struct termios termios_default;
 /// @param tty_fd   TTY file descriptor, or -1 if not in a terminal.
 void pty_process_save_termios(int tty_fd)
 {
+  if (embedded_mode) {
+    // TODO(bfredl): currently we cannot use the state of the host terminal in
+    // the server. when the TUI process launches the server, the state has already
+    // changed. we would need to serialize termios_default in the TUI process and
+    // transmit it. Altough, just always using the clean slate of init_termios() might
+    // be preferrable anyway.
+    return;
+  }
   if (tty_fd == -1) {
     return;
   }
diff --git a/src/nvim/ui_client.c b/src/nvim/ui_client.c
index 2821054909..ff82fd3239 100644
--- a/src/nvim/ui_client.c
+++ b/src/nvim/ui_client.c
@@ -41,8 +41,11 @@ uint64_t ui_client_start_server(int argc, char **argv)
   }
   args[args_idx++] = NULL;
 
+  CallbackReader on_err = CALLBACK_READER_INIT;
+  on_err.fwd_err = true;
+
   Channel *channel = channel_job_start(args, CALLBACK_READER_INIT,
-                                       CALLBACK_READER_INIT, CALLBACK_NONE,
+                                       on_err, CALLBACK_NONE,
                                        false, true, true, false, kChannelStdinPipe,
                                        NULL, 0, 0, NULL, &exit_status);
   if (ui_client_forward_stdin) {