{"abstract":"An escaped pipe splits a field, or an even run of escape characters hides a real separator.","category":"Parsing","checks":7,"contract":"Split a pipe-delimited string. Only backslash-pipe and backslash-backslash are legal escapes. Preserve empty fields; reject incomplete or unknown escapes by returning None.","contract_signature":"text","evaluation_group":"model-20abbcce0abf0136","failed_approach":"A negative lookbehind handles one backslash but mistakes an escaped backslash for an active escape.","family":"parse-escaped-delimiter","id":"FA-171","implementations":{"attempt":{"sha256":"dee3f734a27c681922b3a68085764896bd4a536a45460c0b031fc720b1c97af7","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re\nN = 1\nobservations = []\ndef solve(text):\n    fields = re.split(r'(?<!\\\\)\\|', text)\n    return [value.replace(r'\\|', '|').replace('\\\\\\\\', '\\\\') for value in fields]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nlabel = 'field' * N\ncheck('literal escaped separator', solve(label + r'\\|inside|tail'), [label + '|inside', 'tail'])\ncheck('even escape run leaves separator active', solve(label + '\\\\\\\\|tail'), [label + '\\\\', 'tail'])\ncheck('multiple escaped backslashes', solve('\\\\\\\\' * N + '|end'), ['\\\\' * N, 'end'])\ncheck('empty fields remain positioned', solve('|a||'), ['', 'a', '', ''])\ncheck('empty record is one empty field', solve(''), [''])\ncheck('dangling escape rejected', solve(label + '\\\\'), None)\ncheck('unknown escape rejected', solve(label + r'\\q'), None)\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":"09dfb8f5b8a95787deb4e7c157ce72f4e9da27d437bd2930aed78de4f11aa284","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport re\nN = 1\nobservations = []\ndef solve(text):\n    return text.split('|')\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\nlabel = 'field' * N\ncheck('literal escaped separator', solve(label + r'\\|inside|tail'), [label + '|inside', 'tail'])\ncheck('even escape run leaves separator active', solve(label + '\\\\\\\\|tail'), [label + '\\\\', 'tail'])\ncheck('multiple escaped backslashes', solve('\\\\\\\\' * N + '|end'), ['\\\\' * N, 'end'])\ncheck('empty fields remain positioned', solve('|a||'), ['', 'a', '', ''])\ncheck('empty record is one empty field', solve(''), [''])\ncheck('dangling escape rejected', solve(label + '\\\\'), None)\ncheck('unknown escape rejected', solve(label + r'\\q'), None)\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":"parse-escaped-delimiter","generated_at":"2026-09-29T14:36:51.007774+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Small transport and configuration grammars often need both literal separators and literal escape characters; checking only the previous character loses this distinction.","root_cause":"A delimiter split ignores the escape-state parity immediately before each separator.","sha256":"5d8975f8ccf77174bfea4a7f5c53f84068458f1e31381b3990617f0525667c72","title":"An escaped separator becomes a field boundary · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":29.622,"exit_code":1,"observations":[{"actual":["field|inside","tail"],"check":"literal escaped separator","expected":["field|inside","tail"],"passed":true},{"actual":["field\\|tail"],"check":"even escape run leaves separator active","expected":["field\\","tail"],"passed":false},{"actual":["\\|end"],"check":"multiple escaped backslashes","expected":["\\","end"],"passed":false},{"actual":["","a","",""],"check":"empty fields remain positioned","expected":["","a","",""],"passed":true},{"actual":[""],"check":"empty record is one empty field","expected":[""],"passed":true},{"actual":["field\\"],"check":"dangling escape rejected","expected":null,"passed":false},{"actual":["field\\q"],"check":"unknown escape rejected","expected":null,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"literal escaped separator\", \"actual\": [\"field|inside\", \"tail\"], \"expected\": [\"field|inside\", \"tail\"], \"passed\": true}, {\"check\": \"even escape run leaves separator active\", \"actual\": [\"field\\\\|tail\"], \"expected\": [\"field\\\\\", \"tail\"], \"passed\": false}, {\"check\": \"multiple escaped backslashes\", \"actual\": [\"\\\\|end\"], \"expected\": [\"\\\\\", \"end\"], \"passed\": false}, {\"check\": \"empty fields remain positioned\", \"actual\": [\"\", \"a\", \"\", \"\"], \"expected\": [\"\", \"a\", \"\", \"\"], \"passed\": true}, {\"check\": \"empty record is one empty field\", \"actual\": [\"\"], \"expected\": [\"\"], \"passed\": true}, {\"check\": \"dangling escape rejected\", \"actual\": [\"field\\\\\"], \"expected\": null, \"passed\": false}, {\"check\": \"unknown escape rejected\", \"actual\": [\"field\\\\q\"], \"expected\": null, \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":33.007,"exit_code":1,"observations":[{"actual":["field\\","inside","tail"],"check":"literal escaped separator","expected":["field|inside","tail"],"passed":false},{"actual":["field\\\\","tail"],"check":"even escape run leaves separator active","expected":["field\\","tail"],"passed":false},{"actual":["\\\\","end"],"check":"multiple escaped backslashes","expected":["\\","end"],"passed":false},{"actual":["","a","",""],"check":"empty fields remain positioned","expected":["","a","",""],"passed":true},{"actual":[""],"check":"empty record is one empty field","expected":[""],"passed":true},{"actual":["field\\"],"check":"dangling escape rejected","expected":null,"passed":false},{"actual":["field\\q"],"check":"unknown escape rejected","expected":null,"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"literal escaped separator\", \"actual\": [\"field\\\\\", \"inside\", \"tail\"], \"expected\": [\"field|inside\", \"tail\"], \"passed\": false}, {\"check\": \"even escape run leaves separator active\", \"actual\": [\"field\\\\\\\\\", \"tail\"], \"expected\": [\"field\\\\\", \"tail\"], \"passed\": false}, {\"check\": \"multiple escaped backslashes\", \"actual\": [\"\\\\\\\\\", \"end\"], \"expected\": [\"\\\\\", \"end\"], \"passed\": false}, {\"check\": \"empty fields remain positioned\", \"actual\": [\"\", \"a\", \"\", \"\"], \"expected\": [\"\", \"a\", \"\", \"\"], \"passed\": true}, {\"check\": \"empty record is one empty field\", \"actual\": [\"\"], \"expected\": [\"\"], \"passed\": true}, {\"check\": \"dangling escape rejected\", \"actual\": [\"field\\\\\"], \"expected\": null, \"passed\": false}, {\"check\": \"unknown escape rejected\", \"actual\": [\"field\\\\q\"], \"expected\": null, \"passed\": false}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}