Bug report

Bug description:

in PEP 814, the provided pseudocode for hash(frozendict) is hash(frozenset(frozendict.items())), which makes sense, but the current implementation severely mismatches it in semantics:

just xoring the key and value hashes is very different from xoring the proper hashes of (key, value) pairs
the current implementation causes collisions to arise on permutations of keys and values separately rather than treating each entry as a single unit:

cases= [
  {"a": False, "b": True, "c": True},
  {"a": True, "b": False, "c": True},
  {"a": True, "b": True, "c": False},
  {False: "a", "b": True, "c": True},
  {"a": "b", False: True, True: "c"}
]
assert len({hash(frozendict(case)) for case in cases}) == 1

which is definitely not desirable, and potentially even exploitable for DOS attacks like string hashes were before randomization was added.

CPython versions tested on:

3.15

Operating systems tested on:

Linux

Linked PRs

• gh-149807 : frozendict_hash : hash (key, value) pairs rather than keys and values separately #149808
• gh-149807: Fix hash(frozendict): compute (key, value) pair hash #149841
• [3.15] gh-149807: Fix hash(frozendict): compute (key, value) pair hash (GH-149841) #150149