support signatures to signal decorator

dbus_next/service.py

@@ -107,17 +107,16 @@ def wrapped(*args, **kwargs):
 
 
 class _Signal:
-    def __init__(self, fn, name, disabled=False):
+    def __init__(self, fn, name, disabled=False, signature: Optional[str] = None):
         inspection = inspect.signature(fn)
 
         args = []
-        signature = ''
         signature_tree = None
 
-        return_annotation = parse_annotation(inspection.return_annotation)
+        if signature is None:
+            signature = parse_annotation(inspection.return_annotation)
 
-        if return_annotation:
-            signature = return_annotation
+        if signature:
             signature_tree = SignatureTree._get(signature)
             for type_ in signature_tree.types:
                 args.append(intr.Arg(type_, intr.ArgDirection.OUT))
@@ -132,7 +131,7 @@ def __init__(self, fn, name, disabled=False):
         self.introspection = intr.Signal(self.name, args)
 
 
-def signal(name: str = None, disabled: bool = False):
+def signal(name: str = None, disabled: bool = False, signature: Optional[str] = None):
     """A decorator to mark a class method of a :class:`ServiceInterface` to be a DBus signal.
 
     The signal is broadcast on the bus when the decorated class method is
@@ -170,7 +169,7 @@ def two_strings_signal(self, val1, val2) -> 'ss':
     @no_type_check_decorator
     def decorator(fn):
         fn_name = name if name else fn.__name__
-        signal = _Signal(fn, fn_name, disabled)
+        signal = _Signal(fn, fn_name, disabled, signature)
 
         @wraps(fn)
         def wrapped(self, *args, **kwargs):

test/service/test_decorators.py

@@ -62,6 +62,10 @@ def foo_prop(self) -> int:
     def foo_prop(self, val: int):
         self._foo_prop = val
 
+    @signal(signature="as")
+    def foo_signal(self) -> List[str]:
+        return ['result']
+
 
 def test_method_decorator():
     interface = ExampleInterface()
@@ -96,7 +100,7 @@ def test_method_decorator():
     assert not method.disabled
     assert type(method.introspection) is intr.Method
 
-    assert len(signals) == 2
+    assert len(signals) == 3
 
     signal = signals[0]
     assert signal.name == 'renamed_signal'
@@ -105,6 +109,12 @@ def test_method_decorator():
     assert type(signal.introspection) is intr.Signal
 
     signal = signals[1]
+    assert signal.name == 'foo_signal'
+    assert signal.signature == 'as'
+    assert not signal.disabled
+    assert type(signal.introspection) is intr.Signal
+
+    signal = signals[2]
     assert signal.name == 'some_signal'
     assert signal.signature == 'as'
     assert not signal.disabled
@@ -177,7 +187,7 @@ def test_interface_introspection():
     signals = xml.findall('signal')
     properties = xml.findall('property')
 
-    assert len(xml) == 6
+    assert len(xml) == 7
     assert len(methods) == 2
-    assert len(signals) == 1
+    assert len(signals) == 2
     assert len(properties) == 3