Add rel_path_keyword to @method (fd.o #11623)

2 files changed, 41 insertions, 2 deletions

diff --git a/dbus/decorators.py b/dbus/decorators.py
index 908d055..00cf20d 100644
--- a/dbus/decorators.py
+++ b/dbus/decorators.py
@@ -35,7 +35,8 @@ def method(dbus_interface, in_signature=None, out_signature=None,
         async_callbacks=None,
         sender_keyword=None, path_keyword=None, destination_keyword=None,
         message_keyword=None, connection_keyword=None,
-        utf8_strings=False, byte_arrays=False):
+        utf8_strings=False, byte_arrays=False,
+        rel_path_keyword=None):
     """Factory for decorators used to mark methods of a `dbus.service.Object`
     to be exported on the D-Bus.
 
@@ -86,8 +87,20 @@ def method(dbus_interface, in_signature=None, out_signature=None,
             case of "fallback paths" you'll usually want to use the object
             path in the method's implementation.
 
+            For fallback objects, `rel_path_keyword` (new in 0.82.2) is
+            likely to be more useful.
+
             :Since: 0.80.0?
 
+        `rel_path_keyword` : str or None
+            If not None (the default), the decorated method will receive
+            the destination object path, relative to the path at which the
+            object was exported, as a keyword argument with this
+            name. For non-fallback objects the relative path will always be
+            '/'.
+
+            :Since: 0.82.2
+
         `destination_keyword` : str or None
             If not None (the default), the decorated method will receive
             the destination bus name as a keyword argument with this name.
@@ -150,6 +163,8 @@ def method(dbus_interface, in_signature=None, out_signature=None,
 
         if sender_keyword:
             args.remove(sender_keyword)
+        if rel_path_keyword:
+            args.remove(rel_path_keyword)
         if path_keyword:
             args.remove(path_keyword)
         if destination_keyword:
@@ -174,6 +189,7 @@ def method(dbus_interface, in_signature=None, out_signature=None,
         func._dbus_out_signature = out_signature
         func._dbus_sender_keyword = sender_keyword
         func._dbus_path_keyword = path_keyword
+        func._dbus_rel_path_keyword = rel_path_keyword
         func._dbus_destination_keyword = destination_keyword
         func._dbus_message_keyword = message_keyword
         func._dbus_connection_keyword = connection_keyword
diff --git a/dbus/service.py b/dbus/service.py
index 8ffec3e..21165c5 100644
--- a/dbus/service.py
+++ b/dbus/service.py
@@ -33,7 +33,7 @@ except ImportError:
 
 import _dbus_bindings
 from dbus import SessionBus, Signature, Struct, validate_bus_name, \
-                 validate_object_path, INTROSPECTABLE_IFACE
+                 validate_object_path, INTROSPECTABLE_IFACE, ObjectPath
 from dbus.decorators import method, signal
 from dbus.exceptions import DBusException, \
                             NameExistsException, \
@@ -653,6 +653,29 @@ class Object(Interface):
                 keywords[parent_method._dbus_sender_keyword] = message.get_sender()
             if parent_method._dbus_path_keyword:
                 keywords[parent_method._dbus_path_keyword] = message.get_path()
+            if parent_method._dbus_rel_path_keyword:
+                path = message.get_path()
+                rel_path = path
+                for exp in self._locations:
+                    # pathological case: if we're exported in two places,
+                    # one of which is a subtree of the other, then pick the
+                    # subtree by preference (i.e. minimize the length of
+                    # rel_path)
+                    if exp[0] is connection:
+                        if path == exp[1]:
+                            rel_path = '/'
+                            break
+                        if exp[1] == '/':
+                            # we already have rel_path == path at the beginning
+                            continue
+                        if path.startswith(exp[1] + '/'):
+                            # yes we're in this exported subtree
+                            suffix = path[len(exp[1]):]
+                            if len(suffix) < len(rel_path):
+                                rel_path = suffix
+                rel_path = ObjectPath(rel_path)
+                keywords[parent_method._dbus_rel_path_keyword] = rel_path
+
             if parent_method._dbus_destination_keyword:
                 keywords[parent_method._dbus_destination_keyword] = message.get_destination()
             if parent_method._dbus_message_keyword: