Raise AttributeError on attempts to access unset oneof fields (#510)

tests/inputs/google_impl_behavior_equivalence/test_google_impl_behavior_equivalence.py

@@ -50,8 +50,10 @@ def test_bytes_are_the_same_for_oneof():
 
     # None of these fields were explicitly set BUT they should not actually be null
     # themselves
-    assert isinstance(message.foo, Foo)
-    assert isinstance(message2.foo, Foo)
+    assert not hasattr(message, "foo")
+    assert object.__getattribute__(message, "foo") == betterproto.PLACEHOLDER
+    assert not hasattr(message2, "foo")
+    assert object.__getattribute__(message2, "foo") == betterproto.PLACEHOLDER
 
     assert isinstance(message_reference.foo, ReferenceFoo)
     assert isinstance(message_reference2.foo, ReferenceFoo)

tests/inputs/oneof_enum/test_oneof_enum.py

@@ -18,9 +18,8 @@ def test_which_one_of_returns_enum_with_default_value():
         get_test_case_json_data("oneof_enum", "oneof_enum-enum-0.json")[0].json
     )
 
-    assert message.move == Move(
-        x=0, y=0
-    )  # Proto3 will default this as there is no null
+    assert not hasattr(message, "move")
+    assert object.__getattribute__(message, "move") == betterproto.PLACEHOLDER
     assert message.signal == Signal.PASS
     assert betterproto.which_one_of(message, "action") == ("signal", Signal.PASS)
 
@@ -33,9 +32,8 @@ def test_which_one_of_returns_enum_with_non_default_value():
     message.from_json(
         get_test_case_json_data("oneof_enum", "oneof_enum-enum-1.json")[0].json
     )
-    assert message.move == Move(
-        x=0, y=0
-    )  # Proto3 will default this as there is no null
+    assert not hasattr(message, "move")
+    assert object.__getattribute__(message, "move") == betterproto.PLACEHOLDER
     assert message.signal == Signal.RESIGN
     assert betterproto.which_one_of(message, "action") == ("signal", Signal.RESIGN)
 
@@ -44,5 +42,6 @@ def test_which_one_of_returns_second_field_when_set():
     message = Test()
     message.from_json(get_test_case_json_data("oneof_enum")[0].json)
     assert message.move == Move(x=2, y=3)
-    assert message.signal == Signal.PASS
+    assert not hasattr(message, "signal")
+    assert object.__getattribute__(message, "signal") == betterproto.PLACEHOLDER
     assert betterproto.which_one_of(message, "action") == ("move", Move(x=2, y=3))

tests/oneof_pattern_matching.py

@@ -0,0 +1,46 @@
+from dataclasses import dataclass
+
+import pytest
+
+import betterproto
+
+
+def test_oneof_pattern_matching():
+    @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(baz="test1", abc="test2")
+
+    match foo:
+        case Foo(bar=_):
+            pytest.fail("Matched 'bar' instead of 'baz'")
+        case Foo(baz=v):
+            assert v == "test1"
+        case _:
+            pytest.fail("Matched neither 'bar' nor 'baz'")
+
+    match foo:
+        case Foo(sub=_):
+            pytest.fail("Matched 'sub' instead of 'abc'")
+        case Foo(abc=v):
+            assert v == "test2"
+        case _:
+            pytest.fail("Matched neither 'sub' nor 'abc'")
+
+    foo.sub = Sub(val=1)
+
+    match foo:
+        case Foo(sub=Sub(val=v)):
+            assert v == 1
+        case Foo(abc=v):
+            pytest.fail("Matched 'abc' instead of 'sub'")
+        case _:
+            pytest.fail("Matched neither 'sub' nor 'abc'")

tests/test_features.py

@@ -1,4 +1,5 @@
 import json
+import sys
 from copy import (
     copy,
     deepcopy,
@@ -18,6 +19,8 @@ from typing import (
     Optional,
 )
 
+import pytest
+
 import betterproto
 
 
@@ -151,17 +154,18 @@ def test_oneof_support():
     foo.baz = "test"
 
     # Other oneof fields should now be unset
-    assert foo.bar == 0
+    assert not hasattr(foo, "bar")
+    assert object.__getattribute__(foo, "bar") == betterproto.PLACEHOLDER
     assert betterproto.which_one_of(foo, "group1")[0] == "baz"
 
-    foo.sub.val = 1
+    foo.sub = 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) is False
+    assert not hasattr(foo, "sub")
+    assert object.__getattribute__(foo, "sub") == betterproto.PLACEHOLDER
     assert betterproto.which_one_of(foo, "group2")[0] == "abc"
 
     # Zero value should always serialize for one-of
@@ -176,6 +180,16 @@ def test_oneof_support():
     assert betterproto.which_one_of(foo2, "group2")[0] == ""
 
 
+@pytest.mark.skipif(
+    sys.version_info < (3, 10),
+    reason="pattern matching is only supported in python3.10+",
+)
+def test_oneof_pattern_matching():
+    from .oneof_pattern_matching import test_oneof_pattern_matching
+
+    test_oneof_pattern_matching()
+
+
 def test_json_casing():
     @dataclass
     class CasingTest(betterproto.Message):