FA-4421 / Mapping semantics / Open access

Map filter keys not values · case 01

The operation returns a result or retained state that violates this contract: Keep entries whose keys occur in the supplied allowed-key list, retaining map insertion order.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The predicate tests values against an allowed-key collection.

VERIFIED REPAIR

Keep entries whose keys occur in the supplied allowed-key list, retaining map insertion order.

Unsuccessful approach: Iterating the allowlist gives its order precedence over map insertion order.

Case contract

Keep entries whose keys occur in the supplied allowed-key list, retaining map insertion order. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.

Why this case matters

A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x, y=None):
    return [[k,v] for k,v in x.items() if v in y]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('key differs from value', solve({'a': 'b', 'b': 'c'}, ['a']), [['a', 'b']])
check('allowed order ignored', solve({'a': 1, 'b': 2}, ['b', 'a']), [['a', 1], ['b', 2]])
check('empty filter', solve({'a': 1}, []), [])
check('empty map', solve({}, ['a']), [])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
key differs from value	`[]`	`[['a', 'b']]`	Failed
allowed order ignored	`[]`	`[['a', 1], ['b', 2]]`	Failed
empty filter	`[]`	`[]`	Passed
empty map	`[]`	`[]`	Passed

SHA-256 / 1dea5cb3dc4cf4ee826b8bd22ab118e95b3de30d92ed9aea6cf5b37591a0d3f4

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x, y=None):
    return [[k,x[k]] for k in y if k in x]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('key differs from value', solve({'a': 'b', 'b': 'c'}, ['a']), [['a', 'b']])
check('allowed order ignored', solve({'a': 1, 'b': 2}, ['b', 'a']), [['a', 1], ['b', 2]])
check('empty filter', solve({'a': 1}, []), [])
check('empty map', solve({}, ['a']), [])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
key differs from value	`[['a', 'b']]`	`[['a', 'b']]`	Passed
allowed order ignored	`[['b', 2], ['a', 1]]`	`[['a', 1], ['b', 2]]`	Failed
empty filter	`[]`	`[]`	Passed
empty map	`[]`	`[]`	Passed

SHA-256 / 73529d36ae8bf2538256002596b0a793dfae26f43b70ca38e67ba59c0a2de5d0

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x, y=None):
    return [[k,v] for k,v in x.items() if k in y]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('key differs from value', solve({'a': 'b', 'b': 'c'}, ['a']), [['a', 'b']])
check('allowed order ignored', solve({'a': 1, 'b': 2}, ['b', 'a']), [['a', 1], ['b', 2]])
check('empty filter', solve({'a': 1}, []), [])
check('empty map', solve({}, ['a']), [])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
key differs from value	`[['a', 'b']]`	`[['a', 'b']]`	Passed
allowed order ignored	`[['a', 1], ['b', 2]]`	`[['a', 1], ['b', 2]]`	Passed
empty filter	`[]`	`[]`	Passed
empty map	`[]`	`[]`	Passed

SHA-256 / 7beab73bfd41f86dc767a411ddcbe3858d3b908685c30e0504debba3c7a90400

Verification & scope

This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:37:39.018564+00:00.

Case digest / eb4ca79ea81e641f053b44cc573ab83a58a27f0b15e807ee0a55ae90b99101d7