FA-3916 / Regular expressions / Open access

A minimal token matcher yields empty tokens between characters · case 01

A minimal token matcher yields empty tokens between characters.

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

ROOT CAUSE

The implementation applies an operation whose text or grammar semantics violate this contract: Extract nonempty quoted bodies, allowing backslash-escaped characters.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Extract nonempty quoted bodies, allowing backslash-escaped characters.

Unsuccessful approach: The attempted repair handles the primary example but still violates a separate boundary of the same contract.

Case contract

Extract nonempty quoted bodies, allowing backslash-escaped characters.

Why this case matters

A local executable model for consumers of structured text; oracle values are authored literals, not outputs copied from the repaired implementation.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return re.findall(r'"(.*?)"',x)
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('""'), [])
check('boundary 2', solve('"a\\"b"'), ['a\\"b'])
check('boundary 3', solve('"abc"'), ['abc'])
check('boundary 4', solve('none'), [])
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
boundary 1	`['']`	`[]`	Failed
boundary 2	`['a\\']`	`['a\\"b']`	Failed
boundary 3	`['abc']`	`['abc']`	Passed
boundary 4	`[]`	`[]`	Passed

SHA-256 / 58204faece05da6fea2b1bb246b56086029603f3fea6cd40f4d4e1130bce7b63

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return re.findall(r'"(.+?)"',x)
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('""'), [])
check('boundary 2', solve('"a\\"b"'), ['a\\"b'])
check('boundary 3', solve('"abc"'), ['abc'])
check('boundary 4', solve('none'), [])
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
boundary 1	`[]`	`[]`	Passed
boundary 2	`['a\\']`	`['a\\"b']`	Failed
boundary 3	`['abc']`	`['abc']`	Passed
boundary 4	`[]`	`[]`	Passed

SHA-256 / f63bd2de7b2b0dcf318a07660d5cf05ea2f833761fc58137cac4c63edb713855

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import re, unicodedata, json, csv, io, html, base64, binascii, codecs, struct
from urllib.parse import quote, unquote, unquote_to_bytes, urlencode, parse_qsl, urlsplit, urlunsplit
from email.header import decode_header, make_header
from email.utils import getaddresses
from xml.etree import ElementTree as ET
import shlex, string, textwrap

N = 1
observations = []
def solve(x):
    try:
        return re.findall(r'"((?:[^"\\]|\\.)+)"',x)
    except Exception as exc:
        return {"error": type(exc).__name__}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('boundary 1', solve('""'), [])
check('boundary 2', solve('"a\\"b"'), ['a\\"b'])
check('boundary 3', solve('"abc"'), ['abc'])
check('boundary 4', solve('none'), [])
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
boundary 1	`[]`	`[]`	Passed
boundary 2	`['a\\"b']`	`['a\\"b']`	Passed
boundary 3	`['abc']`	`['abc']`	Passed
boundary 4	`[]`	`[]`	Passed

SHA-256 / e7df2ba3bf7872d38d50ee815c5f51fa3813425732b14b96ca817fa133063f23

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 2026-09-29T14:37:32.784531+00:00.

Case digest / 12907bb81ced420e0412e81fb1110068db279901b30a444dab4a71bc926b2173