rfc8785: ensure IntEnum works on < 3.11 (#5)

* rfc8785: ensure IntEnum works on < 3.11

Signed-off-by: William Woodruff <william@trailofbits.com>

* rfc8785: generalize coercion

Signed-off-by: William Woodruff <william@trailofbits.com>

* test_impl: test StrEnum as well

Signed-off-by: William Woodruff <william@trailofbits.com>

* test_impl: skip StrEnum test below 3.11

Since StrEnum does not exist.

Signed-off-by: William Woodruff <william@trailofbits.com>

* test_impl: fix import

Signed-off-by: William Woodruff <william@trailofbits.com>

---------

Signed-off-by: William Woodruff <william@trailofbits.com>

src/rfc8785/_impl.py

@@ -189,6 +189,11 @@ def dump(obj: _Value, sink: IO[bytes]) -> None:
             else:
                 sink.write(b"false")
         case int():
+            # Annoyance: int can be subclassed by types like IntEnum,
+            # which then break or change `int.__str__`. Rather than plugging
+            # these individually, we coerce back to `int`.
+            obj = int(obj)
+
             if obj < _INT_MIN or obj > _INT_MAX:
                 raise IntegerDomainError(obj)
             sink.write(str(obj).encode("utf-8"))

test/test_impl.py

@@ -5,6 +5,7 @@
 import gzip
 import json
 import struct
+import sys
 from enum import IntEnum
 from io import BytesIO
 
@@ -112,3 +113,17 @@ class X(IntEnum):
 
     raw = impl.dumps([X.A, X.B, X.C])
     assert json.loads(raw) == [1, 2, 9001]
+
+
+@pytest.mark.skipif(sys.version_info < (3, 11), reason="StrEnum added in 3.11+")
+def test_dumps_strenum():
+    from enum import StrEnum
+
+    # StrEnum is a subclass of str, so this should work transparently.
+    class X(StrEnum):
+        A = "foo"
+        B = "bar"
+        C = "baz"
+
+    raw = impl.dumps([X.A, X.B, X.C])
+    assert json.loads(raw) == ["foo", "bar", "baz"]