Do not close panes until process has exited and any outstanding data

has been written to the pipe-pane event if there is one. GitHub issue 991.

cmd-pipe-pane.c

@@ -35,6 +35,7 @@
 
 static enum cmd_retval	cmd_pipe_pane_exec(struct cmd *, struct cmdq_item *);
 
+static void cmd_pipe_pane_write_callback(struct bufferevent *, void *);
 static void cmd_pipe_pane_error_callback(struct bufferevent *, short, void *);
 
 const struct cmd_entry cmd_pipe_pane_entry = {
@@ -68,6 +69,11 @@ cmd_pipe_pane_exec(struct cmd *self, struct cmdq_item *item)
 		bufferevent_free(wp->pipe_event);
 		close(wp->pipe_fd);
 		wp->pipe_fd = -1;
+
+		if (window_pane_destroy_ready(wp)) {
+			server_destroy_pane(wp, 1);
+			return (CMD_RETURN_NORMAL);
+		}
 	}
 
 	/* If no pipe command, that is enough. */
@@ -131,8 +137,9 @@ cmd_pipe_pane_exec(struct cmd *self, struct cmdq_item *item)
 		wp->pipe_fd = pipe_fd[0];
 		wp->pipe_off = EVBUFFER_LENGTH(wp->event->input);
 
-		wp->pipe_event = bufferevent_new(wp->pipe_fd,
+		wp->pipe_event = bufferevent_new(wp->pipe_fd, NULL,
-		    NULL, NULL, cmd_pipe_pane_error_callback, wp);
+		    cmd_pipe_pane_write_callback, cmd_pipe_pane_error_callback,
+		    wp);
 		bufferevent_enable(wp->pipe_event, EV_WRITE);
 
 		setblocking(wp->pipe_fd, 0);
@@ -142,13 +149,28 @@ cmd_pipe_pane_exec(struct cmd *self, struct cmdq_item *item)
 	}
 }
 
+static void
+cmd_pipe_pane_write_callback(__unused struct bufferevent *bufev, void *data)
+{
+	struct window_pane	*wp = data;
+
+	log_debug("%%%u pipe empty", wp->id);
+	if (window_pane_destroy_ready(wp))
+		server_destroy_pane(wp, 1);
+}
+
 static void
 cmd_pipe_pane_error_callback(__unused struct bufferevent *bufev,
     __unused short what, void *data)
 {
 	struct window_pane	*wp = data;
 
+	log_debug("%%%u pipe error", wp->id);
+
 	bufferevent_free(wp->pipe_event);
 	close(wp->pipe_fd);
 	wp->pipe_fd = -1;
+
+	if (window_pane_destroy_ready(wp))
+		server_destroy_pane(wp, 1);
 }

server.c

@@ -406,7 +406,12 @@ server_child_exited(pid_t pid, int status)
 		TAILQ_FOREACH(wp, &w->panes, entry) {
 			if (wp->pid == pid) {
 				wp->status = status;
-				server_destroy_pane(wp, 1);
+
+				log_debug("%%%u exited", wp->id);
+				wp->flags |= PANE_EXITED;
+
+				if (window_pane_destroy_ready(wp))
+					server_destroy_pane(wp, 1);
 				break;
 			}
 		}

tmux.h

@@ -768,6 +768,8 @@ struct window_pane {
 #define PANE_FOCUSPUSH 0x20
 #define PANE_INPUTOFF 0x40
 #define PANE_CHANGED 0x80
+#define PANE_ERROR 0x100
+#define PANE_EXITED 0x200
 
 	int		 argc;
 	char	       **argv;
@@ -2133,6 +2135,7 @@ u_int		 window_count_panes(struct window *);
 void		 window_destroy_panes(struct window *);
 struct window_pane *window_pane_find_by_id_str(const char *);
 struct window_pane *window_pane_find_by_id(u_int);
+int		 window_pane_destroy_ready(struct window_pane *);
 int		 window_pane_spawn(struct window_pane *, int, char **,
 		     const char *, const char *, const char *, struct environ *,
 		     struct termios *, char **);
@@ -2154,7 +2157,6 @@ void		 window_pane_key(struct window_pane *, struct client *,
 int		 window_pane_outside(struct window_pane *);
 int		 window_pane_visible(struct window_pane *);
 u_int		 window_pane_search(struct window_pane *, const char *);
-
 const char	*window_printable_flags(struct winlink *);
 struct window_pane *window_pane_find_up(struct window_pane *);
 struct window_pane *window_pane_find_down(struct window_pane *);

window.c

@@ -388,6 +388,19 @@ window_destroy(struct window *w)
 	free(w);
 }
 
+int
+window_pane_destroy_ready(struct window_pane *wp)
+{
+	if (wp->pipe_fd != -1 && EVBUFFER_LENGTH(wp->pipe_event->output) != 0)
+		return (0);
+
+	if (~wp->flags & PANE_EXITED)
+		return (0);
+	if (~wp->flags & PANE_ERROR)
+		return (0);
+	return (1);
+}
+
 void
 window_add_ref(struct window *w, const char *from)
 {
@@ -1000,7 +1013,11 @@ window_pane_error_callback(__unused struct bufferevent *bufev,
 {
 	struct window_pane *wp = data;
 
-	server_destroy_pane(wp, 1);
+	log_debug("%%%u error", wp->id);
+	wp->flags |= PANE_ERROR;
+
+	if (window_pane_destroy_ready(wp))
+		server_destroy_pane(wp, 1);
 }
 
 void