[gnome-online-accounts/wip/rishi/issue-43] daemon, dbus: Enable checking if a provider type is supported

[Debarshi Ray <debarshir src gnome org>]

commit 95fb22b0bbe8c3ba244ac614fb916c24af58921d
Author: Debarshi Ray <debarshir gnome org>
Date:   Mon Feb 3 20:01:18 2020 +0100

    daemon, dbus: Enable checking if a provider type is supported
    
    With the advent of Flatpak, applications can no longer be expected to
    be updated in lockstep with the operating system. In this case,
    applications are meant to link against libgoa-1.0.so, while goa-daemon
    and libgoa-backend-1.0.so are considered part of the OS.
    
    Therefore, when a newer version of an application is running against
    an older operating system, it needs to introspect the provider types
    supported by the backend daemon so that features not supported by the
    OS can be disabled at run-time.
    
    Based on initial work done by Jean Felder.
    
    https://gitlab.gnome.org/GNOME/gnome-online-accounts/issues/43

 data/dbus-interfaces.xml |  5 +++++
 src/daemon/goadaemon.c   | 27 +++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)
---
diff --git a/data/dbus-interfaces.xml b/data/dbus-interfaces.xml
index 2fa79824..6ac52f02 100644
--- a/data/dbus-interfaces.xml
+++ b/data/dbus-interfaces.xml
@@ -421,6 +421,11 @@
       <arg name="account_object_path" type="o" direction="out"/>
     </method>
 
+    <method name="IsSupportedProvider">
+      <arg name="provider_type" type="s" direction="in"/>
+      <arg name="is_supported" type="b" direction="out"/>
+    </method>
+
   </interface>
 
 
diff --git a/src/daemon/goadaemon.c b/src/daemon/goadaemon.c
index bfbe41c8..0eb372eb 100644
--- a/src/daemon/goadaemon.c
+++ b/src/daemon/goadaemon.c
@@ -76,6 +76,12 @@ static gboolean on_manager_handle_add_account (GoaManager            *object,
                                                GVariant              *details,
                                                gpointer               user_data);
 
+static gboolean
+on_manager_handle_is_supported_provider (GoaManager             *manager,
+                                         GDBusMethodInvocation  *invocation,
+                                         const gchar            *provider_type,
+                                         gpointer                user_data);
+
 static gboolean on_account_handle_remove (GoaAccount            *account,
                                           GDBusMethodInvocation *invocation,
                                           gpointer               user_data);
@@ -265,6 +271,7 @@ goa_daemon_init (GoaDaemon *self)
                     "handle-add-account",
                     G_CALLBACK (on_manager_handle_add_account),
                     self);
+  g_signal_connect (self->manager, "handle-is-supported-provider", G_CALLBACK 
(on_manager_handle_is_supported_provider), NULL);
   object = goa_object_skeleton_new ("/org/gnome/OnlineAccounts/Manager");
   goa_object_skeleton_set_manager (object, self->manager);
   g_dbus_object_manager_server_export (self->object_manager, G_DBUS_OBJECT_SKELETON (object));
@@ -1292,6 +1299,26 @@ on_manager_handle_add_account (GoaManager             *manager,
 
 /* ---------------------------------------------------------------------------------------------------- */
 
+static gboolean
+on_manager_handle_is_supported_provider (GoaManager             *manager,
+                                         GDBusMethodInvocation  *invocation,
+                                         const gchar            *provider_type,
+                                         gpointer                user_data)
+{
+  GoaProvider *provider = NULL;
+  gboolean is_supported;
+
+  provider = goa_provider_get_for_provider_type (provider_type);
+  is_supported = provider == NULL ? FALSE : TRUE;
+
+  goa_manager_complete_is_supported_provider (manager, invocation, is_supported);
+
+  g_clear_object (&provider);
+  return TRUE;
+}
+
+/* ---------------------------------------------------------------------------------------------------- */
+
 typedef struct
 {
   GoaObject *object;