Add OneOf support, rework field detection

betterproto/tests/test_features.py

@@ -13,23 +13,23 @@ def test_has_field():
 
     # Unset by default
     foo = Foo()
-    assert foo.bar.serialized_on_wire == False
+    assert betterproto.serialized_on_wire(foo.bar) == False
 
     # Serialized after setting something
     foo.bar.baz = 1
-    assert foo.bar.serialized_on_wire == True
+    assert betterproto.serialized_on_wire(foo.bar) == True
 
     # Still has it after setting the default value
     foo.bar.baz = 0
-    assert foo.bar.serialized_on_wire == True
+    assert betterproto.serialized_on_wire(foo.bar) == True
 
-    # Manual override
-    foo.bar.serialized_on_wire = False
-    assert foo.bar.serialized_on_wire == False
+    # Manual override (don't do this)
+    foo.bar._serialized_on_wire = False
+    assert betterproto.serialized_on_wire(foo.bar) == False
 
     # Can manually set it but defaults to false
     foo.bar = Bar()
-    assert foo.bar.serialized_on_wire == False
+    assert betterproto.serialized_on_wire(foo.bar) == False
 
 
 def test_enum_as_int_json():
@@ -70,3 +70,48 @@ def test_unknown_fields():
 
     new_again = Newer().parse(round_trip)
     assert newer == new_again
+
+
+def test_oneof_support():
+    @dataclass
+    class Sub(betterproto.Message):
+        val: int = betterproto.int32_field(1)
+
+    @dataclass
+    class Foo(betterproto.Message):
+        bar: int = betterproto.int32_field(1, group="group1")
+        baz: str = betterproto.string_field(2, group="group1")
+        sub: Sub = betterproto.message_field(3, group="group2")
+        abc: str = betterproto.string_field(4, group="group2")
+
+    foo = Foo()
+
+    assert betterproto.which_one_of(foo, "group1")[0] == ""
+
+    foo.bar = 1
+    foo.baz = "test"
+
+    # Other oneof fields should now be unset
+    assert foo.bar == 0
+    assert betterproto.which_one_of(foo, "group1")[0] == "baz"
+
+    foo.sub.val = 1
+    assert betterproto.serialized_on_wire(foo.sub)
+
+    foo.abc = "test"
+
+    # Group 1 shouldn't be touched, group 2 should have reset
+    assert foo.sub.val == 0
+    assert betterproto.serialized_on_wire(foo.sub) == False
+    assert betterproto.which_one_of(foo, "group2")[0] == "abc"
+
+    # Zero value should always serialize for one-of
+    foo = Foo(bar=0)
+    assert betterproto.which_one_of(foo, "group1")[0] == "bar"
+    assert bytes(foo) == b"\x08\x00"
+
+    # Round trip should also work
+    foo2 = Foo().parse(bytes(foo))
+    assert betterproto.which_one_of(foo2, "group1")[0] == "bar"
+    assert foo.bar == 0
+    assert betterproto.which_one_of(foo2, "group2")[0] == ""