tests: Move fake-document-portal subprocess inside dbus-appinfo test

For the reasons given in
https://gitlab.gnome.org/GNOME/glib/-/merge_requests/4176#note_2233317,
it’s best to not rely on subprocesses when writing tests. Spawning a
subprocess can go wrong, getting feedback and assertion data from a
subprocess is a pain, and making sure the subprocess is killed properly
at the end of the test is hard to get right.

For tests where we are trying to mock a D-Bus service, it’s much more
reliable to run that service in-process (either in the main thread or in
a separate thread).

So, do that for the `fake-document-portal` former subprocess in the
`dbus-appinfo` test: move it to a worker thread.

This speeds the test up, simplifies the build slightly, and should make
the test run more reliable.

In particular, it provides a pattern for future `fake-*-portal` tests to
be built off. This is particularly useful for more complex portals,
where data needs to be relayed back from the mock portal service to the
unit test to check that the code under test has behaved properly. That’s
a pain to do from a subprocess.

Delete the `org.freedesktop.portal.Documents.service` file because we no
longer need to rely on D-Bus service activation within the test, as
we’re setting up the mock service thread explicitly now.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

gio/tests/dbus-appinfo.c

@@ -23,6 +23,7 @@
 #include <gio/gdesktopappinfo.h>
 
 #include "gdbus-sessionbus.h"
+#include "fake-document-portal.h"
 
 static GDesktopAppInfo *appinfo;
 static int current_state;
@@ -348,9 +349,14 @@ test_flatpak_doc_export (void)
   GDesktopAppInfo *flatpak_appinfo;
   GApplication *app;
   int status;
+  GFakeDocumentPortalThread *thread = NULL;
 
   g_test_summary ("Test that files launched via Flatpak apps are made available via the document portal.");
 
+  /* Run a fake-document-portal */
+  thread = g_fake_document_portal_thread_new (session_bus_get_address ());
+  g_fake_document_portal_thread_run (thread);
+
   desktop_file = g_test_build_filename (G_TEST_DIST,
                                         "org.gtk.test.dbusappinfo.flatpak.desktop",
                                         NULL);
@@ -369,6 +375,8 @@ test_flatpak_doc_export (void)
 
   g_object_unref (app);
   g_object_unref (flatpak_appinfo);
+  g_fake_document_portal_thread_stop (thread);
+  g_clear_object (&thread);
 }
 
 static void
@@ -426,9 +434,14 @@ test_flatpak_missing_doc_export (void)
   GDesktopAppInfo *flatpak_appinfo;
   GApplication *app;
   int status;
+  GFakeDocumentPortalThread *thread = NULL;
 
   g_test_summary ("Test that files launched via Flatpak apps are made available via the document portal.");
 
+  /* Run a fake-document-portal */
+  thread = g_fake_document_portal_thread_new (session_bus_get_address ());
+  g_fake_document_portal_thread_run (thread);
+
   desktop_file = g_test_build_filename (G_TEST_DIST,
                                         "org.gtk.test.dbusappinfo.flatpak.desktop",
                                         NULL);
@@ -447,6 +460,8 @@ test_flatpak_missing_doc_export (void)
   g_object_unref (app);
   g_object_unref (flatpak_appinfo);
   g_free (desktop_file);
+  g_fake_document_portal_thread_stop (thread);
+  g_clear_object (&thread);
 }
 
 int

gio/tests/fake-document-portal.c

@@ -26,8 +26,56 @@
 #include <gio/gio.h>
 #include <gio/gunixfdlist.h>
 
+#include "fake-document-portal.h"
 #include "fake-document-portal-generated.h"
 
+struct _GFakeDocumentPortalThread
+{
+  GObject parent_instance;
+
+  char *address;  /* (not nullable) */
+  GCancellable *cancellable;  /* (not nullable) (owned) */
+  GThread *thread;  /* (not nullable) (owned) */
+  GCond cond;  /* (mutex mutex) */
+  GMutex mutex;
+  gboolean ready;  /* (mutex mutex) */
+};
+
+G_DEFINE_FINAL_TYPE (GFakeDocumentPortalThread, g_fake_document_portal_thread, G_TYPE_OBJECT)
+
+static void g_fake_document_portal_thread_finalize (GObject *object);
+
+static void
+g_fake_document_portal_thread_class_init (GFakeDocumentPortalThreadClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  gobject_class->finalize = g_fake_document_portal_thread_finalize;
+}
+
+static void
+g_fake_document_portal_thread_init (GFakeDocumentPortalThread *self)
+{
+  self->cancellable = g_cancellable_new ();
+  g_cond_init (&self->cond);
+  g_mutex_init (&self->mutex);
+}
+
+static void
+g_fake_document_portal_thread_finalize (GObject *object)
+{
+  GFakeDocumentPortalThread *self = G_FAKE_DOCUMENT_PORTAL_THREAD (object);
+
+  g_assert (self->thread == NULL);  /* should already have been joined */
+
+  g_mutex_clear (&self->mutex);
+  g_cond_clear (&self->cond);
+  g_clear_object (&self->cancellable);
+  g_clear_pointer (&self->address, g_free);
+
+  G_OBJECT_CLASS (g_fake_document_portal_thread_parent_class)->finalize (object);
+}
+
 static gboolean
 on_handle_get_mount_point (FakeDocuments         *object,
                            GDBusMethodInvocation *invocation,
@@ -76,13 +124,66 @@ on_handle_add_full (FakeDocuments         *object,
 }
 
 static void
-on_bus_acquired (GDBusConnection *connection,
+on_name_acquired (GDBusConnection *connection,
                   const gchar     *name,
                   gpointer         user_data)
 {
-  FakeDocuments *interface;
-  GError *error = NULL;
+  GFakeDocumentPortalThread *self = G_FAKE_DOCUMENT_PORTAL_THREAD (user_data);
 
+  g_test_message ("Acquired the name %s", name);
+
+  g_mutex_lock (&self->mutex);
+  self->ready = TRUE;
+  g_cond_signal (&self->cond);
+  g_mutex_unlock (&self->mutex);
+}
+
+static void
+on_name_lost (GDBusConnection *connection,
+              const gchar     *name,
+              gpointer         user_data)
+{
+  g_test_message ("Lost the name %s", name);
+}
+
+static gboolean
+cancelled_cb (GCancellable *cancellable,
+              gpointer      user_data)
+{
+  g_test_message ("fake-document-portal cancelled");
+  return G_SOURCE_CONTINUE;
+}
+
+static gpointer
+fake_document_portal_thread_cb (gpointer user_data)
+{
+  GFakeDocumentPortalThread *self = G_FAKE_DOCUMENT_PORTAL_THREAD (user_data);
+  GMainContext *context = NULL;
+  GDBusConnection *connection = NULL;
+  GSource *source = NULL;
+  guint id;
+  FakeDocuments *interface = NULL;
+  GError *local_error = NULL;
+
+  context = g_main_context_new ();
+  g_main_context_push_thread_default (context);
+
+  connection = g_dbus_connection_new_for_address_sync (self->address,
+                                                       G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT |
+                                                       G_DBUS_CONNECTION_FLAGS_MESSAGE_BUS_CONNECTION,
+                                                       NULL,
+                                                       self->cancellable,
+                                                       &local_error);
+  g_assert_no_error (local_error);
+
+  /* Listen for cancellation. The source will wake up the context iteration
+   * which can then re-check its exit condition below. */
+  source = g_cancellable_source_new (self->cancellable);
+  g_source_set_callback (source, G_SOURCE_FUNC (cancelled_cb), NULL, NULL);
+  g_source_attach (source, context);
+  g_source_unref (source);
+
+  /* Set up the interface */
   g_test_message ("Acquired a message bus connection");
 
   interface = fake_documents_skeleton_new ();
@@ -98,51 +199,81 @@ on_bus_acquired (GDBusConnection *connection,
   g_dbus_interface_skeleton_export (G_DBUS_INTERFACE_SKELETON (interface),
                                     connection,
                                     "/org/freedesktop/portal/documents",
-                                    &error);
-  g_assert_no_error (error);
-}
+                                    &local_error);
+  g_assert_no_error (local_error);
 
-static void
-on_name_acquired (GDBusConnection *connection,
-                  const gchar     *name,
-                  gpointer         user_data)
-{
-  g_test_message ("Acquired the name %s", name);
-}
-
-static void
-on_name_lost (GDBusConnection *connection,
-              const gchar     *name,
-              gpointer         user_data)
-{
-  g_test_message ("Lost the name %s", name);
-}
-
-
-gint
-main (gint argc, gchar *argv[])
-{
-  GMainLoop *loop;
-  guint id;
-
-  g_log_writer_default_set_use_stderr (TRUE);
-
-  loop = g_main_loop_new (NULL, FALSE);
-
-  id = g_bus_own_name (G_BUS_TYPE_SESSION,
+  /* Own the portal name */
+  id = g_bus_own_name_on_connection (connection,
                                      "org.freedesktop.portal.Documents",
                                      G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT |
                                      G_BUS_NAME_OWNER_FLAGS_REPLACE,
-                       on_bus_acquired,
                                      on_name_acquired,
                                      on_name_lost,
-                       loop,
+                                     self,
                                      NULL);
 
-  g_main_loop_run (loop);
+  while (!g_cancellable_is_cancelled (self->cancellable))
+    g_main_context_iteration (context, TRUE);
 
   g_bus_unown_name (id);
-  g_main_loop_unref (loop);
+  g_dbus_interface_skeleton_unexport (G_DBUS_INTERFACE_SKELETON (interface));
+  g_clear_object (&interface);
+  g_clear_object (&connection);
+  g_main_context_pop_thread_default (context);
+  g_clear_pointer (&context, g_main_context_unref);
 
-  return 0;
+  return NULL;
+}
+
+/*
+ * Create a new #GFakeDocumentPortalThread. The thread isn’t started until
+ * g_fake_document_portal_thread_run() is called on it.
+ *
+ * Returns: (transfer full): the new fake document portal wrapper
+ */
+GFakeDocumentPortalThread *
+g_fake_document_portal_thread_new (const char *address)
+{
+  GFakeDocumentPortalThread *self = g_object_new (G_TYPE_FAKE_DOCUMENT_PORTAL_THREAD, NULL);
+  self->address = g_strdup (address);
+  return g_steal_pointer (&self);
+}
+
+/*
+ * Start a worker thread which will run a fake
+ * `org.freedesktop.portal.Documents` portal on the bus at @address. This is
+ * intended to be used with #GTestDBus to mock up a portal from within a unit
+ * test process, rather than relying on D-Bus activation of a mock portal
+ * subprocess.
+ *
+ * It blocks until the thread has owned its D-Bus name and is ready to handle
+ * requests.
+ */
+void
+g_fake_document_portal_thread_run (GFakeDocumentPortalThread *self)
+{
+  g_return_if_fail (G_IS_FAKE_DOCUMENT_PORTAL_THREAD (self));
+  g_return_if_fail (self->thread == NULL);
+
+  self->thread = g_thread_new ("fake-document-portal", fake_document_portal_thread_cb, self);
+
+  /* Block until the thread is ready. */
+  g_mutex_lock (&self->mutex);
+  while (!self->ready)
+    g_cond_wait (&self->cond, &self->mutex);
+  g_mutex_unlock (&self->mutex);
+}
+
+/* Stop and join a worker thread started with fake_document_portal_thread_run().
+ * Blocks until the thread has stopped and joined.
+ *
+ * Once this has been called, it’s safe to drop the final reference on @self. */
+void
+g_fake_document_portal_thread_stop (GFakeDocumentPortalThread *self)
+{
+  g_return_if_fail (G_IS_FAKE_DOCUMENT_PORTAL_THREAD (self));
+  g_return_if_fail (self->thread != NULL);
+
+  g_cancellable_cancel (self->cancellable);
+  g_thread_join (g_steal_pointer (&self->thread));
 }

gio/tests/fake-document-portal.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2024 GNOME Foundation
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __FAKE_DOCUMENT_PORTAL_H__
+#define __FAKE_DOCUMENT_PORTAL_H__
+
+#include <glib.h>
+#include <glib-object.h>
+
+G_BEGIN_DECLS
+
+#define G_TYPE_FAKE_DOCUMENT_PORTAL_THREAD (g_fake_document_portal_thread_get_type ())
+G_DECLARE_FINAL_TYPE (GFakeDocumentPortalThread, g_fake_document_portal_thread, G, FAKE_DOCUMENT_PORTAL_THREAD, GObject)
+
+GFakeDocumentPortalThread *g_fake_document_portal_thread_new (const char *address);
+void g_fake_document_portal_thread_run (GFakeDocumentPortalThread *self);
+void g_fake_document_portal_thread_stop (GFakeDocumentPortalThread *self);
+
+G_END_DECLS
+
+#endif /* __FAKE_DOCUMENT_PORTAL_H__ */

gio/tests/meson.build

@@ -544,15 +544,6 @@ if host_machine.system() != 'windows'
       },
     }
 
-    if not glib_have_cocoa
-      gio_tests += {
-        'dbus-appinfo' : {
-          'extra_sources' : extra_sources,
-          'extra_programs' : ['fake-document-portal'],
-        },
-      }
-    endif
-
     fake_document_portal_generated = custom_target('fake-document-portal-generated',
         input :   ['../org.freedesktop.portal.Documents.xml'],
         output :  ['fake-document-portal-generated.h',
@@ -566,10 +557,15 @@ if host_machine.system() != 'windows'
                    '--c-namespace', 'Fake',
                    '@INPUT@'])
 
-    test_extra_programs += {
-      'fake-document-portal' : {
-        'extra_sources': fake_document_portal_generated,
+    if not glib_have_cocoa
+      gio_tests += {
+        'dbus-appinfo' : {
+          'extra_sources' : [extra_sources, 'fake-document-portal.c', fake_document_portal_generated],
         },
+      }
+    endif
+
+    test_extra_programs += {
       'fake-service-name' : {}
     }
   endif # have_dbus_daemon

gio/tests/services/meson.build

@@ -1,5 +1,4 @@
 dbus_service_files = [
-  'org.freedesktop.portal.Documents.service',
   'org.gtk.GDBus.FakeService.service'
 ]
 

gio/tests/services/org.freedesktop.portal.Documents.service.in

@@ -1,3 +0,0 @@
-[D-BUS Service]
-Name=org.freedesktop.portal.Documents
-Exec=@installed_tests_dir@/fake-document-portal