FA-3086 / Regular expressions / Open access

A multiline quoted block stops at a newline · case 01

A multiline quoted block stops at a newline.

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 text strictly between BEGIN and END, including newlines; return None for no full match.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Extract text strictly between BEGIN and END, including newlines; return None for no full match.

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

Case contract

Extract text strictly between BEGIN and END, including newlines; return None for no full match.

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.fullmatch(r'BEGIN(.*)END',x).group(1) if re.fullmatch(r'BEGIN(.*)END',x) else None)
    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('BEGINa\nbEND'), 'a\nb')
check('boundary 2', solve('BEGINEND'), '')
check('boundary 3', solve('BEGINxEND'), 'x')
check('boundary 4', solve('xBEGINaEND'), 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	`None`	`a b`	Failed
boundary 2			Passed
boundary 3	`x`	`x`	Passed
boundary 4	`None`	`None`	Passed

SHA-256 / fea6cded8f4b45d48a41644968a859c5a4d8bd53b4cc8dd3e191817a8e69bd4e

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.fullmatch(r'BEGIN(.*?)END',x,re.MULTILINE).group(1) if re.fullmatch(r'BEGIN(.*?)END',x,re.MULTILINE) else None)
    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('BEGINa\nbEND'), 'a\nb')
check('boundary 2', solve('BEGINEND'), '')
check('boundary 3', solve('BEGINxEND'), 'x')
check('boundary 4', solve('xBEGINaEND'), 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	`None`	`a b`	Failed
boundary 2			Passed
boundary 3	`x`	`x`	Passed
boundary 4	`None`	`None`	Passed

SHA-256 / 5177eff6927aca18f7c14a27a27a54db9233dd0a72112f84956a08703dee8019

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.fullmatch(r'BEGIN(.*)END',x,re.DOTALL).group(1) if re.fullmatch(r'BEGIN(.*)END',x,re.DOTALL) else None)
    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('BEGINa\nbEND'), 'a\nb')
check('boundary 2', solve('BEGINEND'), '')
check('boundary 3', solve('BEGINxEND'), 'x')
check('boundary 4', solve('xBEGINaEND'), 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	`a b`	`a b`	Passed
boundary 2			Passed
boundary 3	`x`	`x`	Passed
boundary 4	`None`	`None`	Passed

SHA-256 / f8f1cfe54e68dbc4740cf43433ae8c6e0f6f2ec508ad4bfe65c5b435bbddfc31

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 2026-09-29T14:37:21.341205+00:00.

Case digest / e1fb473de1bfdbc852f857c266b4c8ff1eed7890021a698bf0fff02228aa4daa