Add a testcase for notify-in-instance-init

This is reproducing a problem that was observed
in gtk3's gtk_check_button_init.

gobject/tests/meson.build

@@ -29,6 +29,7 @@ marshalers_c = custom_target('marshalers_c',
 )
 
 gobject_tests = {
+  'notify-init' : {},
   'qdata' : {},
   'accumulator' : {
     'source' : ['accumulator.c', marshalers_h, marshalers_c],

gobject/tests/notify-init.c

@@ -0,0 +1,268 @@
+/* GLib testing framework examples and tests
+ * Copyright (C) 2022 Red Hat, Inc.
+ *
+ * This work is provided "as is"; redistribution and modification
+ * in whole or in part, in any medium, physical or electronic is
+ * permitted without restriction.
+ *
+ * This work 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.
+ *
+ * In no event shall the authors or contributors be liable for any
+ * direct, indirect, incidental, special, exemplary, or consequential
+ * damages (including, but not limited to, procurement of substitute
+ * goods or services; loss of use, data, or profits; or business
+ * interruption) however caused and on any theory of liability, whether
+ * in contract, strict liability, or tort (including negligence or
+ * otherwise) arising in any way out of the use of this software, even
+ * if advised of the possibility of such damage.
+ */
+
+#include <stdlib.h>
+#include <gstdio.h>
+#include <glib-object.h>
+
+typedef struct {
+  GObject parent_instance;
+  gint foo;
+  gboolean bar;
+  gchar *baz;
+  gchar *quux;
+} TestObject;
+
+typedef struct {
+  GObjectClass parent_class;
+} TestObjectClass;
+
+typedef enum {
+  PROP_FOO = 1,
+  PROP_BAR,
+  PROP_BAZ,
+  PROP_QUUX,
+  N_PROPERTIES
+} TestObjectProperty;
+
+static GParamSpec *properties[N_PROPERTIES] = { NULL, };
+
+static GType test_object_get_type (void);
+G_DEFINE_TYPE (TestObject, test_object, G_TYPE_OBJECT)
+
+static void
+test_object_set_foo (TestObject *obj,
+                     gint        foo)
+{
+  if (obj->foo != foo)
+    {
+      obj->foo = foo;
+
+      g_assert (properties[PROP_FOO] != NULL);
+      g_object_notify_by_pspec (G_OBJECT (obj), properties[PROP_FOO]);
+    }
+}
+
+static void
+test_object_set_bar (TestObject *obj,
+                     gboolean    bar)
+{
+  bar = !!bar;
+
+  if (obj->bar != bar)
+    {
+      obj->bar = bar;
+
+      g_assert (properties[PROP_BAR] != NULL);
+      g_object_notify_by_pspec (G_OBJECT (obj), properties[PROP_BAR]);
+    }
+}
+
+static void
+test_object_set_baz (TestObject  *obj,
+                     const gchar *baz)
+{
+  if (g_strcmp0 (obj->baz, baz) != 0)
+    {
+      g_free (obj->baz);
+      obj->baz = g_strdup (baz);
+
+      g_assert (properties[PROP_BAZ] != NULL);
+      g_object_notify_by_pspec (G_OBJECT (obj), properties[PROP_BAZ]);
+    }
+}
+
+static void
+test_object_set_quux (TestObject  *obj,
+                      const gchar *quux)
+{
+  if (g_strcmp0 (obj->quux, quux) != 0)
+    {
+      g_free (obj->quux);
+      obj->quux = g_strdup (quux);
+
+      g_assert (properties[PROP_QUUX] != NULL);
+      g_object_notify_by_pspec (G_OBJECT (obj), properties[PROP_QUUX]);
+    }
+}
+
+static void
+test_object_finalize (GObject *gobject)
+{
+  TestObject *self = (TestObject *) gobject;
+
+  g_free (self->baz);
+  g_free (self->quux);
+
+  G_OBJECT_CLASS (test_object_parent_class)->finalize (gobject);
+}
+
+static void
+test_object_set_property (GObject *gobject,
+                          guint prop_id,
+                          const GValue *value,
+                          GParamSpec *pspec)
+{
+  TestObject *tobj = (TestObject *) gobject;
+
+  g_assert_cmpint (prop_id, !=, 0);
+  g_assert_cmpint (prop_id, !=, N_PROPERTIES);
+  g_assert (pspec == properties[prop_id]);
+
+  switch ((TestObjectProperty)prop_id)
+    {
+    case PROP_FOO:
+      test_object_set_foo (tobj, g_value_get_int (value));
+      break;
+
+    case PROP_BAR:
+      test_object_set_bar (tobj, g_value_get_boolean (value));
+      break;
+
+    case PROP_BAZ:
+      test_object_set_baz (tobj, g_value_get_string (value));
+      break;
+
+    case PROP_QUUX:
+      test_object_set_quux (tobj, g_value_get_string (value));
+      break;
+
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static void
+test_object_get_property (GObject *gobject,
+                          guint prop_id,
+                          GValue *value,
+                          GParamSpec *pspec)
+{
+  TestObject *tobj = (TestObject *) gobject;
+
+  g_assert_cmpint (prop_id, !=, 0);
+  g_assert_cmpint (prop_id, !=, N_PROPERTIES);
+  g_assert (pspec == properties[prop_id]);
+
+  switch ((TestObjectProperty)prop_id)
+    {
+    case PROP_FOO:
+      g_value_set_int (value, tobj->foo);
+      break;
+
+    case PROP_BAR:
+      g_value_set_boolean (value, tobj->bar);
+      break;
+
+    case PROP_BAZ:
+      g_value_set_string (value, tobj->baz);
+      break;
+
+    case PROP_QUUX:
+      g_value_set_string (value, tobj->quux);
+      break;
+
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static void
+test_object_class_init (TestObjectClass *klass)
+{
+  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
+
+  properties[PROP_FOO] = g_param_spec_int ("foo", "Foo", "Foo",
+                                           -1, G_MAXINT,
+                                           0,
+                                           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
+  properties[PROP_BAR] = g_param_spec_boolean ("bar", "Bar", "Bar",
+                                               FALSE,
+                                               G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
+  properties[PROP_BAZ] = g_param_spec_string ("baz", "Baz", "Baz",
+                                              NULL,
+                                              G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
+
+  properties[PROP_QUUX] = g_param_spec_string ("quux", "quux", "quux",
+                                               NULL,
+                                               G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY | G_PARAM_STATIC_STRINGS);
+
+  gobject_class->set_property = test_object_set_property;
+  gobject_class->get_property = test_object_get_property;
+  gobject_class->finalize = test_object_finalize;
+
+  g_object_class_install_properties (gobject_class, N_PROPERTIES, properties);
+}
+
+static void
+quux_changed (TestObject *self,
+              GParamSpec *pspec,
+              gpointer    data)
+{
+  g_assert (self->baz != NULL);
+}
+
+static void
+test_object_init (TestObject *self)
+{
+  /* This instance init behavior is the thing we are testing:
+   *
+   * 1. Connect to notify::quux
+   * 2. Change the the quux property
+   * 3. Continue to set up things that the quux_changed handler
+   *   relies on
+   *
+   * The expected behavior is that:
+   *
+   * - The quux_changed handler *is* called
+   * - It is only called after the object is fully constructed
+   */
+  g_signal_connect (self, "notify::quux", G_CALLBACK (quux_changed), NULL);
+
+  test_object_set_quux (self, "quux");
+
+  self->foo = 42;
+  self->bar = TRUE;
+  self->baz = g_strdup ("Hello");
+}
+
+static void
+test_notify_in_init (void)
+{
+  TestObject *obj;
+
+  g_test_summary ("Test that emitting notify with a handler already connected in test_object_init() works");
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/2665");
+
+  obj = g_object_new (test_object_get_type (), NULL);
+
+  g_object_unref (obj);
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/properties/notify-in-init", test_notify_in_init);
+
+  return g_test_run ();
+}