{"abstract":"Writes to the shadow field instead of the descriptor backing key and changes the required Python-language result.","category":"Descriptor lookup","checks":4,"contract":"A data descriptor field takes precedence over an instance field shadow. Its backing key is _value, missing reads return 7, writes update that key, deletion removes it, and class access returns class-descriptor. Return [read results,final instance dictionary]. Inputs use the finite Python types shown in the fixtures. An error string denotes the specified caught exception, not an unhandled process failure.","evaluation_group":"xl-data-descriptor-storage","failed_approach":"The alternative still fails because it deletes the shadow key instead of the descriptor backing key.","family":"xl-data-descriptor-storage-setter-wrong-storage","id":"FA-4961","implementations":{"attempt":{"sha256":"cc634026c7515a32b5489d04fff6bb0849757a9a555aca248d454778165d75c0","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(initial, commands):\n    class D:\n        def __get__(self, obj, owner):\n            if obj is None: return 'class-descriptor'\n            return obj.__dict__.get('_value',7)\n        def __set__(self, obj, value):\n            obj.__dict__['_value']=value\n        def __delete__(self, obj):\n            obj.__dict__.pop('field',None)\n    class C:\n        field=D()\n    c=C(); c.__dict__.update(initial); out=[]\n    for op,value in commands:\n        if op=='get': out.append(c.field)\n        elif op=='class': out.append(C.field)\n        elif op=='set': c.field=value\n        elif op=='delete': del c.field\n    return [out,dict(c.__dict__)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('descriptor beats shadow', solve({'field': 99, '_value': 2}, [['get', None], ['class', None]]), [[2, 'class-descriptor'], {'field': 99, '_value': 2}])\ncheck('set and delete dispatch', solve({}, [['set', 5], ['get', None], ['delete', None], ['get', None]]), [[5, 7], {}])\ncheck('zero is stored', solve({'_value': 0}, [['get', None]]), [[0], {'_value': 0}])\ncheck('shadow survives descriptor delete', solve({'field': 4, '_value': 8}, [['delete', None], ['get', None]]), [[7], {'field': 4}])\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":"76f6a5aba90662e6a90051b42d16a63253d1825d83c06e7c9ffb7f162ba8d1ac","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(initial, commands):\n    class D:\n        def __get__(self, obj, owner):\n            if obj is None: return 'class-descriptor'\n            return obj.__dict__.get('_value',7)\n        def __set__(self, obj, value):\n            obj.__dict__['field']=value\n        def __delete__(self, obj):\n            obj.__dict__.pop('_value',None)\n    class C:\n        field=D()\n    c=C(); c.__dict__.update(initial); out=[]\n    for op,value in commands:\n        if op=='get': out.append(c.field)\n        elif op=='class': out.append(C.field)\n        elif op=='set': c.field=value\n        elif op=='delete': del c.field\n    return [out,dict(c.__dict__)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('descriptor beats shadow', solve({'field': 99, '_value': 2}, [['get', None], ['class', None]]), [[2, 'class-descriptor'], {'field': 99, '_value': 2}])\ncheck('set and delete dispatch', solve({}, [['set', 5], ['get', None], ['delete', None], ['get', None]]), [[5, 7], {}])\ncheck('zero is stored', solve({'_value': 0}, [['get', None]]), [[0], {'_value': 0}])\ncheck('shadow survives descriptor delete', solve({'field': 4, '_value': 8}, [['delete', None], ['get', None]]), [[7], {'field': 4}])\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":"27a2a5cc04c0bd5a04bb91f5efa124d7580b8de85d4df8668b76c112e7842118","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(initial, commands):\n    class D:\n        def __get__(self, obj, owner):\n            if obj is None: return 'class-descriptor'\n            return obj.__dict__.get('_value',7)\n        def __set__(self, obj, value):\n            obj.__dict__['_value']=value\n        def __delete__(self, obj):\n            obj.__dict__.pop('_value',None)\n    class C:\n        field=D()\n    c=C(); c.__dict__.update(initial); out=[]\n    for op,value in commands:\n        if op=='get': out.append(c.field)\n        elif op=='class': out.append(C.field)\n        elif op=='set': c.field=value\n        elif op=='delete': del c.field\n    return [out,dict(c.__dict__)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('descriptor beats shadow', solve({'field': 99, '_value': 2}, [['get', None], ['class', None]]), [[2, 'class-descriptor'], {'field': 99, '_value': 2}])\ncheck('set and delete dispatch', solve({}, [['set', 5], ['get', None], ['delete', None], ['get', None]]), [[5, 7], {}])\ncheck('zero is stored', solve({'_value': 0}, [['get', None]]), [[0], {'_value': 0}])\ncheck('shadow survives descriptor delete', solve({'field': 4, '_value': 8}, [['delete', None], ['get', None]]), [[7], {'field': 4}])\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":"xl-data-descriptor-storage-setter-wrong-storage","generated_at":"2026-09-29T14:37:44.534542+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Runs Python standard-library language operations in a deterministic local reproducer. Literal expected answers are authored independently. Related defects share an evaluation group to avoid benchmark split leakage.","repair":"A data descriptor field takes precedence over an instance field shadow. Its backing key is _value, missing reads return 7, writes update that key, deletion removes it, and class access returns class-descriptor. Return [read results,final instance dictionary].","root_cause":"Writes to the shadow field instead of the descriptor backing key. The executable reproducer isolates this operation from the rest of the contract.","sha256":"645f950fcbe19bbe2b726de30aa41ed47ea4de7a3064136a2e2787f05a49e0b5","title":"Data descriptor storage: Writes to the shadow field instead of the descriptor backing key · case 01","variant":1,"variant_policy":"The five numbered cases rerun the same authored boundary fixtures; they are reproducibility runs, not independent input variants.","verification":{"attempt":{"elapsed_ms":39.554,"exit_code":1,"observations":[{"actual":[[2,"class-descriptor"],{"_value":2,"field":99}],"check":"descriptor beats shadow","expected":[[2,"class-descriptor"],{"_value":2,"field":99}],"passed":true},{"actual":[[5,5],{"_value":5}],"check":"set and delete dispatch","expected":[[5,7],{}],"passed":false},{"actual":[[0],{"_value":0}],"check":"zero is stored","expected":[[0],{"_value":0}],"passed":true},{"actual":[[8],{"_value":8}],"check":"shadow survives descriptor delete","expected":[[7],{"field":4}],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"descriptor beats shadow\", \"actual\": [[2, \"class-descriptor\"], {\"field\": 99, \"_value\": 2}], \"expected\": [[2, \"class-descriptor\"], {\"field\": 99, \"_value\": 2}], \"passed\": true}, {\"check\": \"set and delete dispatch\", \"actual\": [[5, 5], {\"_value\": 5}], \"expected\": [[5, 7], {}], \"passed\": false}, {\"check\": \"zero is stored\", \"actual\": [[0], {\"_value\": 0}], \"expected\": [[0], {\"_value\": 0}], \"passed\": true}, {\"check\": \"shadow survives descriptor delete\", \"actual\": [[8], {\"_value\": 8}], \"expected\": [[7], {\"field\": 4}], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":124.066,"exit_code":1,"observations":[{"actual":[[2,"class-descriptor"],{"_value":2,"field":99}],"check":"descriptor beats shadow","expected":[[2,"class-descriptor"],{"_value":2,"field":99}],"passed":true},{"actual":[[7,7],{"field":5}],"check":"set and delete dispatch","expected":[[5,7],{}],"passed":false},{"actual":[[0],{"_value":0}],"check":"zero is stored","expected":[[0],{"_value":0}],"passed":true},{"actual":[[7],{"field":4}],"check":"shadow survives descriptor delete","expected":[[7],{"field":4}],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"descriptor beats shadow\", \"actual\": [[2, \"class-descriptor\"], {\"field\": 99, \"_value\": 2}], \"expected\": [[2, \"class-descriptor\"], {\"field\": 99, \"_value\": 2}], \"passed\": true}, {\"check\": \"set and delete dispatch\", \"actual\": [[7, 7], {\"field\": 5}], \"expected\": [[5, 7], {}], \"passed\": false}, {\"check\": \"zero is stored\", \"actual\": [[0], {\"_value\": 0}], \"expected\": [[0], {\"_value\": 0}], \"passed\": true}, {\"check\": \"shadow survives descriptor delete\", \"actual\": [[7], {\"field\": 4}], \"expected\": [[7], {\"field\": 4}], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":37.854,"exit_code":0,"observations":[{"actual":[[2,"class-descriptor"],{"_value":2,"field":99}],"check":"descriptor beats shadow","expected":[[2,"class-descriptor"],{"_value":2,"field":99}],"passed":true},{"actual":[[5,7],{}],"check":"set and delete dispatch","expected":[[5,7],{}],"passed":true},{"actual":[[0],{"_value":0}],"check":"zero is stored","expected":[[0],{"_value":0}],"passed":true},{"actual":[[7],{"field":4}],"check":"shadow survives descriptor delete","expected":[[7],{"field":4}],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"descriptor beats shadow\", \"actual\": [[2, \"class-descriptor\"], {\"field\": 99, \"_value\": 2}], \"expected\": [[2, \"class-descriptor\"], {\"field\": 99, \"_value\": 2}], \"passed\": true}, {\"check\": \"set and delete dispatch\", \"actual\": [[5, 7], {}], \"expected\": [[5, 7], {}], \"passed\": true}, {\"check\": \"zero is stored\", \"actual\": [[0], {\"_value\": 0}], \"expected\": [[0], {\"_value\": 0}], \"passed\": true}, {\"check\": \"shadow survives descriptor delete\", \"actual\": [[7], {\"field\": 4}], \"expected\": [[7], {\"field\": 4}], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}