{"abstract":"The operation returns a result or retained state that violates this contract: Membership is true if any scope contains the key, regardless of its value.","category":"Scoped mappings","checks":4,"contract":"Membership is true if any scope contains the key, regardless of its value. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","evaluation_group":"model-430630f9c2996d5d","failed_approach":"Boolean lookup conflates absent keys with present falsy values.","family":"xr-chainmap-membership-searches-all-scopes","id":"FA-4741","implementations":{"attempt":{"sha256":"f6c689c97cc6f4944368813e2883d553d8a9fe9967a5c925d11f707a150eb38f","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom collections import Counter, ChainMap, deque\nimport heapq\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return bool(ChainMap(*x).get(y))\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('outer membership', solve([{}, {'a': 1}], 'a'), True)\ncheck('None present', solve([{'a': None}], 'a'), True)\ncheck('absent', solve([{}, {}], 'a'), False)\ncheck('false present', solve([{}, {'a': False}], 'a'), True)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"0e67638040ccd149cf1aa454963e2487735763ee6fe22a29dbb9ca663ba2bb39","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom collections import Counter, ChainMap, deque\nimport heapq\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return y in x[0]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('outer membership', solve([{}, {'a': 1}], 'a'), True)\ncheck('None present', solve([{'a': None}], 'a'), True)\ncheck('absent', solve([{}, {}], 'a'), False)\ncheck('false present', solve([{}, {'a': False}], 'a'), True)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"fixed":{"sha256":"18129badb7c8c7eecf26a5e06d04d3fe9571ec4686616634b14361d56cfd41df","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nfrom collections import Counter, ChainMap, deque\nimport heapq\nN = 1\nobservations = []\ndef solve(x, y=None):\n    return y in ChainMap(*x)\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('outer membership', solve([{}, {'a': 1}], 'a'), True)\ncheck('None present', solve([{'a': None}], 'a'), True)\ncheck('absent', solve([{}, {}], 'a'), False)\ncheck('false present', solve([{}, {'a': False}], 'a'), True)\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" 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.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xr-chainmap-membership-searches-all-scopes","generated_at":"2026-09-29T14:37:42.187718+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.","repair":"Membership is true if any scope contains the key, regardless of its value.","root_cause":"Checking only the first scope misses inherited bindings.","sha256":"e6628dd933982999328e8b7f92e933dd7e24a58d943bb93b2e806dea03941a76","title":"Chainmap membership searches all scopes · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verification":{"attempt":{"elapsed_ms":39.214,"exit_code":1,"observations":[{"actual":true,"check":"outer membership","expected":true,"passed":true},{"actual":false,"check":"None present","expected":true,"passed":false},{"actual":false,"check":"absent","expected":false,"passed":true},{"actual":false,"check":"false present","expected":true,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"outer membership\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"None present\", \"actual\": false, \"expected\": true, \"passed\": false}, {\"check\": \"absent\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"false present\", \"actual\": false, \"expected\": true, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":37.758,"exit_code":1,"observations":[{"actual":false,"check":"outer membership","expected":true,"passed":false},{"actual":true,"check":"None present","expected":true,"passed":true},{"actual":false,"check":"absent","expected":false,"passed":true},{"actual":false,"check":"false present","expected":true,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"outer membership\", \"actual\": false, \"expected\": true, \"passed\": false}, {\"check\": \"None present\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"absent\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"false present\", \"actual\": false, \"expected\": true, \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":40.851,"exit_code":0,"observations":[{"actual":true,"check":"outer membership","expected":true,"passed":true},{"actual":true,"check":"None present","expected":true,"passed":true},{"actual":false,"check":"absent","expected":false,"passed":true},{"actual":true,"check":"false present","expected":true,"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"outer membership\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"None present\", \"actual\": true, \"expected\": true, \"passed\": true}, {\"check\": \"absent\", \"actual\": false, \"expected\": false, \"passed\": true}, {\"check\": \"false present\", \"actual\": true, \"expected\": true, \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}