{"abstract":"An absent optional group is conflated with an empty group.","category":"Regular expressions","checks":4,"contract":"Parse a name optionally followed by = and any value; distinguish missing value as None.","evaluation_group":"model-9410d3dd7dcc754b","failed_approach":"The attempted repair handles the primary example but still violates a separate boundary of the same contract.","family":"xp-regex-optional-none","id":"FA-3131","implementations":{"attempt":{"sha256":"b5b5c7d0c861c5d04b513cb42d947da469e32736ea4b8e113d42edadb01ac0db","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        return [x.partition('=')[0],x.partition('=')[2] or None]\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve('a'), ['a', None])\ncheck('boundary 2', solve('a='), ['a', ''])\ncheck('boundary 3', solve('a=b'), ['a', 'b'])\ncheck('boundary 4', solve('='), ['', ''])\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":"d8d799b6eb406c44a7cd4029b9cfefabc287a41a55af96a259ce2f2eb8c62458","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        return x.split('=',1) if '=' in x else [x,'']\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve('a'), ['a', None])\ncheck('boundary 2', solve('a='), ['a', ''])\ncheck('boundary 3', solve('a=b'), ['a', 'b'])\ncheck('boundary 4', solve('='), ['', ''])\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":"f6246f26d74c41a36e8043c9b0fa8b83ee14302455c118762dbc878b6410550c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct\nfrom urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit\nfrom email.header import decode_header, make_header\nfrom email.utils import getaddresses\nfrom xml.etree import ElementTree as ET\nimport shlex, string, textwrap\n\nN = 1\nobservations = []\ndef solve(x):\n    try:\n        return [x.partition('=')[0],x.partition('=')[2] if '=' in x else None]\n    except Exception as exc:\n        return {\"error\": type(exc).__name__}\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('boundary 1', solve('a'), ['a', None])\ncheck('boundary 2', solve('a='), ['a', ''])\ncheck('boundary 3', solve('a=b'), ['a', 'b'])\ncheck('boundary 4', solve('='), ['', ''])\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":"xp-regex-optional-none","generated_at":"2026-09-29T14:37:21.686224+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.","repair":"Implement the complete stated contract, including the boundary fixtures: Parse a name optionally followed by = and any value; distinguish missing value as None.","root_cause":"The implementation applies an operation whose text or grammar semantics violate this contract: Parse a name optionally followed by = and any value; distinguish missing value as None.","sha256":"edfd9720cfdc8d3417971d736c86cc1fd0d100e8ea49ecba75c10f1bd5158fca","title":"An absent optional group is conflated with an empty group · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verification":{"attempt":{"elapsed_ms":58.282,"exit_code":1,"observations":[{"actual":["a",null],"check":"boundary 1","expected":["a",null],"passed":true},{"actual":["a",null],"check":"boundary 2","expected":["a",""],"passed":false},{"actual":["a","b"],"check":"boundary 3","expected":["a","b"],"passed":true},{"actual":["",null],"check":"boundary 4","expected":["",""],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [\"a\", null], \"expected\": [\"a\", null], \"passed\": true}, {\"check\": \"boundary 2\", \"actual\": [\"a\", null], \"expected\": [\"a\", \"\"], \"passed\": false}, {\"check\": \"boundary 3\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [\"\", null], \"expected\": [\"\", \"\"], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":59.048,"exit_code":1,"observations":[{"actual":["a",""],"check":"boundary 1","expected":["a",null],"passed":false},{"actual":["a",""],"check":"boundary 2","expected":["a",""],"passed":true},{"actual":["a","b"],"check":"boundary 3","expected":["a","b"],"passed":true},{"actual":["",""],"check":"boundary 4","expected":["",""],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [\"a\", \"\"], \"expected\": [\"a\", null], \"passed\": false}, {\"check\": \"boundary 2\", \"actual\": [\"a\", \"\"], \"expected\": [\"a\", \"\"], \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [\"\", \"\"], \"expected\": [\"\", \"\"], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":54.943,"exit_code":0,"observations":[{"actual":["a",null],"check":"boundary 1","expected":["a",null],"passed":true},{"actual":["a",""],"check":"boundary 2","expected":["a",""],"passed":true},{"actual":["a","b"],"check":"boundary 3","expected":["a","b"],"passed":true},{"actual":["",""],"check":"boundary 4","expected":["",""],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"boundary 1\", \"actual\": [\"a\", null], \"expected\": [\"a\", null], \"passed\": true}, {\"check\": \"boundary 2\", \"actual\": [\"a\", \"\"], \"expected\": [\"a\", \"\"], \"passed\": true}, {\"check\": \"boundary 3\", \"actual\": [\"a\", \"b\"], \"expected\": [\"a\", \"b\"], \"passed\": true}, {\"check\": \"boundary 4\", \"actual\": [\"\", \"\"], \"expected\": [\"\", \"\"], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}