fix: enforce strict_map_key with object_pairs_hook (#673)

This PR makes it so that `self._strict_map_key` is enforced even when
using `_object_pairs_hook` which didn't use to be the case.

msgpack/fallback.py

@@ -518,9 +518,15 @@ class Unpacker:
                     self._unpack(EX_SKIP)
                 return
             if self._object_pairs_hook is not None:
-                ret = self._object_pairs_hook(
-                    (self._unpack(EX_CONSTRUCT), self._unpack(EX_CONSTRUCT)) for _ in range(n)
-                )
+
+                def _gen():
+                    for _ in range(n):
+                        key = self._unpack(EX_CONSTRUCT)
+                        if self._strict_map_key and type(key) not in (str, bytes):
+                            raise ValueError("%s is not allowed for map key" % str(type(key)))
+                        yield key, self._unpack(EX_CONSTRUCT)
+
+                ret = self._object_pairs_hook(_gen())
             else:
                 ret = {}
                 for _ in range(n):

test/test_except.py

@@ -89,3 +89,17 @@ def test_strict_map_key():
     packed = packb(invalid, use_bin_type=True)
     with raises(ValueError):
         unpackb(packed, raw=False, strict_map_key=True)
+
+
+def test_strict_map_key_with_object_pairs_hook():
+    # strict_map_key should be enforced even when object_pairs_hook is set
+    invalid = {42: "value"}
+    packed = packb(invalid, use_bin_type=True)
+    with raises(ValueError):
+        unpackb(packed, raw=False, strict_map_key=True, object_pairs_hook=list)
+
+    # valid keys (str/bytes) should still work with object_pairs_hook
+    valid = {"key": "value"}
+    packed = packb(valid, use_bin_type=True)
+    result = unpackb(packed, raw=False, strict_map_key=True, object_pairs_hook=list)
+    assert result == [("key", "value")]