[glib/benzea/systemd-transient-scope: 2/2] gdesktopappinfo: Handle task completion from spawn function

[Benjamin Berg <bberg src gnome org>]

commit fb08144484493f293993d3a45ee601f176519606
Author: Benjamin Berg <bberg redhat com>
Date:   Tue Jul 28 12:11:13 2020 +0200

    gdesktopappinfo: Handle task completion from spawn function
    
    This allows delaying the return of the task until all dbus calls (in
    particular the ones to setup the scope) have finished.
    
    This fixes the behaviour of the previous commit which would not
    correctly move the process into the scope if the application exited
    right after the task returned.

 gio/gdesktopappinfo.c | 212 ++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 152 insertions(+), 60 deletions(-)
---
diff --git a/gio/gdesktopappinfo.c b/gio/gdesktopappinfo.c
index c5c774665..4bc5f474a 100644
--- a/gio/gdesktopappinfo.c
+++ b/gio/gdesktopappinfo.c
@@ -2872,11 +2872,29 @@ create_systemd_scope (GDBusConnection *session_bus,
   g_free (unit_name);
 }
 
+typedef struct
+{
+  GTask *task; /* (owned) */
+  int fd;      /* (owned) */
+} ScopeCreatedData;
+
+static void
+scope_created_data_free (ScopeCreatedData *data)
+{
+  g_clear_object (&data->task);
+  if (data->fd >= 0)
+    close (data->fd);
+  data->fd = -1;
+
+  g_free (data);
+}
+
 static void
 systemd_scope_created_cb (GObject *object,
                           GAsyncResult *result,
                           gpointer user_data)
 {
+  ScopeCreatedData *data = user_data;
   GVariant *res = NULL;
   GError *error = NULL;
 
@@ -2887,14 +2905,48 @@ systemd_scope_created_cb (GObject *object,
       g_error_free (error);
     }
 
-  /* Unblock the waiting wrapper binary. */
-  close (GPOINTER_TO_INT (user_data));
+  if (data->task)
+    {
+      gint pending;
+      pending = GPOINTER_TO_INT (g_task_get_task_data (data->task));
+      pending -= 1;
+      g_task_set_task_data (data->task, GINT_TO_POINTER (pending), NULL);
+
+      /* There is a corner case where g_desktop_app_info_launch_uris_with_spawn
+       * may have returned an error already.
+       */
+      if (pending == 0 && !g_task_get_completed (data->task))
+        g_task_return_boolean (data->task, TRUE);
+    }
 
   if (res)
     g_variant_unref (res);
+
+  /* This unblocks the waiting wrapper binary. */
+  scope_created_data_free (data);
 }
 #endif
 
+static void
+launch_uris_with_spawn_flush_cb (GObject *object,
+                                 GAsyncResult *result,
+                                 gpointer user_data)
+{
+  GTask *task = G_TASK (user_data);
+  gint pending;
+
+  g_dbus_connection_flush_finish (G_DBUS_CONNECTION (object), result, NULL);
+
+  pending = GPOINTER_TO_INT (g_task_get_task_data (task));
+  pending -= 1;
+  g_task_set_task_data (task, GINT_TO_POINTER (pending), NULL);
+
+  if (pending == 0)
+    g_task_return_boolean (task, TRUE);
+
+  g_object_unref (task);
+}
+
 static gboolean
 g_desktop_app_info_launch_uris_with_spawn (GDesktopAppInfo *info,
                                            GDBusConnection *session_bus,
@@ -2909,17 +2961,26 @@ g_desktop_app_info_launch_uris_with_spawn (GDesktopAppInfo *info,
                                            gint stdin_fd,
                                            gint stdout_fd,
                                            gint stderr_fd,
+                                           GTask *task,
                                            GError **error_out)
 {
-  gboolean completed = FALSE;
   GList *dup_uris;
   GStrv envp = NULL;
   GError *error = NULL;
   char *sn_id = NULL;
   int argc;
 
+  /* We may get a task to report back on or an error. But never both.
+   * Note that g_desktop_app_info_launch_action is currently passing neither.
+   */
+  g_assert (!(task && error));
   g_return_val_if_fail (info != NULL, FALSE);
 
+  /* Surrounding code must not have set any data on the task
+   * (it is cleared before calling this function). */
+  if (session_bus && task)
+    g_assert (g_task_get_task_data (task) == NULL);
+
   if (launch_context)
     envp = g_app_launch_context_get_environment (launch_context);
   else
@@ -3085,11 +3146,29 @@ g_desktop_app_info_launch_uris_with_spawn (GDesktopAppInfo *info,
       close (wrapper_data.pipe[0]);
 
       if (session_bus)
-        create_systemd_scope (session_bus,
-                              info,
-                              pid,
-                              systemd_scope_created_cb,
-                              GINT_TO_POINTER (wrapper_data.pipe[1]));
+        {
+          ScopeCreatedData *data;
+
+          data = g_new0 (ScopeCreatedData, 1);
+
+          if (task)
+            {
+              gint pending;
+              pending = GPOINTER_TO_INT (g_task_get_task_data (task));
+              pending += 1;
+              g_task_set_task_data (task, GINT_TO_POINTER (pending), NULL);
+
+              data->task = g_object_ref (task);
+            }
+
+          data->fd = wrapper_data.pipe[1];
+
+          create_systemd_scope (session_bus,
+                                info,
+                                pid,
+                                systemd_scope_created_cb,
+                                data);
+        }
       else
         close (wrapper_data.pipe[1]);
 #endif
@@ -3129,14 +3208,56 @@ g_desktop_app_info_launch_uris_with_spawn (GDesktopAppInfo *info,
     }
   while (dup_uris != NULL && !error);
 
-  if (dup_uris == NULL)
-    completed = TRUE;
-
   g_strfreev (envp);
-  if (error)
-    g_propagate_error (error_out, error);
 
-  return completed;
+  if (!error)
+    {
+      if (session_bus && task)
+        {
+          GCancellable *cancellable = g_task_get_cancellable (task);
+          gint pending;
+          pending = GPOINTER_TO_INT (g_task_get_task_data (task));
+          pending += 1;
+          g_task_set_task_data (task, GINT_TO_POINTER (pending), NULL);
+
+          /* FIXME: The D-Bus message from the notify_desktop_launch() function
+           * can be still lost even if flush is called later. See:
+           * https://gitlab.freedesktop.org/dbus/dbus/issues/72
+           */
+          g_dbus_connection_flush (session_bus,
+                                   cancellable,
+                                   launch_uris_with_spawn_flush_cb,
+                                   g_steal_pointer (&task));
+        }
+      else if (session_bus)
+        {
+          /* No task available. */
+          g_dbus_connection_flush (session_bus,
+                                   NULL,
+                                   NULL,
+                                   NULL);
+        }
+      else if (task)
+        {
+          /* Return the given task. */
+          g_task_return_boolean (task, TRUE);
+          g_object_unref (task);
+        }
+
+      return TRUE;
+    }
+  else
+    {
+      if (task)
+        {
+          g_task_return_error (task, g_steal_pointer (&error));
+          g_object_unref (task);
+        }
+      else
+        g_propagate_error (error_out, g_steal_pointer (&error));
+
+      return FALSE;
+    }
 }
 
 static gchar *
@@ -3285,17 +3406,9 @@ g_desktop_app_info_launch_uris_internal (GAppInfo                   *appinfo,
     success = g_desktop_app_info_launch_uris_with_spawn (info, session_bus, info->exec, uris, launch_context,
                                                          spawn_flags, user_setup, user_setup_data,
                                                          pid_callback, pid_callback_data,
-                                                         stdin_fd, stdout_fd, stderr_fd, error);
+                                                         stdin_fd, stdout_fd, stderr_fd, NULL, error);
 
-  if (session_bus != NULL)
-    {
-      /* This asynchronous flush holds a reference until it completes,
-       * which ensures that the following unref won't immediately kill
-       * the connection if we were the initial owner.
-       */
-      g_dbus_connection_flush (session_bus, NULL, NULL, NULL);
-      g_object_unref (session_bus);
-    }
+  g_clear_object (&session_bus);
 
   return success;
 }
@@ -3349,18 +3462,6 @@ launch_uris_with_dbus_cb (GObject      *object,
   g_object_unref (task);
 }
 
-static void
-launch_uris_flush_cb (GObject      *object,
-                      GAsyncResult *result,
-                      gpointer      user_data)
-{
-  GTask *task = G_TASK (user_data);
-
-  g_dbus_connection_flush_finish (G_DBUS_CONNECTION (object), result, NULL);
-  g_task_return_boolean (task, TRUE);
-  g_object_unref (task);
-}
-
 static void
 launch_uris_bus_get_cb (GObject      *object,
                         GAsyncResult *result,
@@ -3369,12 +3470,20 @@ launch_uris_bus_get_cb (GObject      *object,
   GTask *task = G_TASK (user_data);
   GDesktopAppInfo *info = G_DESKTOP_APP_INFO (g_task_get_source_object (task));
   LaunchUrisData *data = g_task_get_task_data (task);
+  LaunchUrisData *data_copy = NULL;
   GCancellable *cancellable = g_task_get_cancellable (task);
   GDBusConnection *session_bus;
-  GError *error = NULL;
 
   session_bus = g_bus_get_finish (result, NULL);
 
+  data_copy = g_new0 (LaunchUrisData, 1);
+  data_copy->appinfo = g_steal_pointer (&data->appinfo);
+  data_copy->uris = g_steal_pointer (&data->uris);
+  data_copy->context = g_steal_pointer (&data->context);
+
+  /* Allow other data to be attached to the task. */
+  g_task_set_task_data (task, NULL, NULL);
+
   if (session_bus && info->app_id)
     {
       /* FIXME: The g_document_portal_add_documents() function, which is called
@@ -3382,34 +3491,21 @@ launch_uris_bus_get_cb (GObject      *object,
        * uses blocking calls.
        */
       g_desktop_app_info_launch_uris_with_dbus (info, session_bus,
-                                                data->uris, data->context,
+                                                data_copy->uris, data_copy->context,
                                                 cancellable,
                                                 launch_uris_with_dbus_cb,
                                                 g_steal_pointer (&task));
     }
   else
     {
-      /* FIXME: The D-Bus message from the notify_desktop_launch() function
-       * can be still lost even if flush is called later. See:
-       * https://gitlab.freedesktop.org/dbus/dbus/issues/72
-       */
       g_desktop_app_info_launch_uris_with_spawn (info, session_bus, info->exec,
-                                                 data->uris, data->context,
+                                                 data_copy->uris, data_copy->context,
                                                  _SPAWN_FLAGS_DEFAULT, NULL,
                                                  NULL, NULL, NULL, -1, -1, -1,
-                                                 &error);
-      if (error != NULL)
-        {
-          g_task_return_error (task, g_steal_pointer (&error));
-          g_object_unref (task);
-        }
-      else
-        g_dbus_connection_flush (session_bus,
-                                 cancellable,
-                                 launch_uris_flush_cb,
-                                 g_steal_pointer (&task));
+                                                 g_steal_pointer (&task), NULL);
     }
 
+  launch_uris_data_free (data_copy);
   g_clear_object (&session_bus);
 }
 
@@ -5225,16 +5321,12 @@ g_desktop_app_info_launch_action (GDesktopAppInfo   *info,
       if (exec_line)
         g_desktop_app_info_launch_uris_with_spawn (info, session_bus, exec_line, NULL, launch_context,
                                                    _SPAWN_FLAGS_DEFAULT, NULL, NULL, NULL, NULL,
-                                                   -1, -1, -1, NULL);
+                                                   -1, -1, -1, NULL, NULL);
 
       g_free (exec_line);
     }
 
-  if (session_bus != NULL)
-    {
-      g_dbus_connection_flush (session_bus, NULL, NULL, NULL);
-      g_object_unref (session_bus);
-    }
+  g_clear_object (&session_bus);
 }
 /* Epilogue {{{1 */