feat: speed up creating Variant objects (#144)

src/dbus_fast/signature.pxd

@@ -19,5 +19,5 @@ cdef class SignatureTree:
 cdef class Variant:
 
     cdef public object type
-    cdef public str signature
+    cdef public object signature
     cdef public object value

src/dbus_fast/signature.py

@@ -405,31 +405,27 @@ class Variant:
         """Init a new Variant."""
         if type(signature) is SignatureTree:
             signature_tree = signature
+            self.signature = signature_tree.signature
+            self.type = signature_tree.types[0]
         elif type(signature) is SignatureType:
-            signature_type = signature
-            signature_str = signature.signature
             signature_tree = None
+            self.signature = signature.signature
+            self.type = signature
         elif type(signature) is str:
             signature_tree = get_signature_tree(signature)
+            self.signature = signature
+            self.type = signature_tree.types[0]
         else:
             raise TypeError(
                 "signature must be a SignatureTree, SignatureType, or a string"
             )
-
-        if signature_tree:
-            if verify and len(signature_tree.types) != 1:
+        self.value = value
+        if verify:
+            if signature_tree and len(signature_tree.types) != 1:
                 raise ValueError(
                     "variants must have a signature for a single complete type"
                 )
-            signature_str = signature_tree.signature
-            signature_type = signature_tree.types[0]
-
-        if verify:
-            signature_type.verify(value)
-
-        self.type = signature_type
-        self.signature = signature_str
-        self.value = value
+            self.type.verify(value)
 
     def __eq__(self, other: Any) -> bool:
         if type(other) is Variant:

tests/test_signature.py

@@ -220,3 +220,14 @@ def test_invalid_variants():
 
     with pytest.raises(SignatureBodyMismatchError):
         tree.verify([con])
+
+
+def test_variant_signature_type():
+    tree = SignatureTree("as")
+    var = Variant(tree.types[0], ["foo", "bar"])
+    assert var.type == tree.types[0]
+    assert var.value == ["foo", "bar"]
+    assert var.signature == "as"
+
+    with pytest.raises(SignatureBodyMismatchError):
+        Variant(tree.types[0], "wrong")