FA-3096 / Regular expressions / Open access

Split delimiters unexpectedly enter the result · case 01

Split delimiters unexpectedly enter the result.

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: Split on one or more comma/semicolon delimiters while preserving terminal empty fields.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Split on one or more comma/semicolon delimiters while preserving terminal empty fields.

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

Case contract

Split on one or more comma/semicolon delimiters while preserving terminal empty fields.

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.split(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('a,b;c'), ['a', 'b', 'c'])
check('boundary 2', solve(',a,'), ['', 'a', ''])
check('boundary 3', solve('a,,b'), ['a', 'b'])
check('boundary 4', solve(''), [''])
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', ';', 'c']`	`['a', 'b', 'c']`	Failed
boundary 2	`['', ',', 'a', ',', '']`	`['', 'a', '']`	Failed
boundary 3	`['a', ',,', 'b']`	`['a', 'b']`	Failed
boundary 4	`['']`	`['']`	Passed

SHA-256 / 5724ace7773d44b064217b56e9d7a9a7d23f2d4441ecfbcaf5c40960a5d80d33

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 [v for v in re.split(r'[,;]+',x) if v]
    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('a,b;c'), ['a', 'b', 'c'])
check('boundary 2', solve(',a,'), ['', 'a', ''])
check('boundary 3', solve('a,,b'), ['a', 'b'])
check('boundary 4', solve(''), [''])
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', 'c']`	`['a', 'b', 'c']`	Passed
boundary 2	`['a']`	`['', 'a', '']`	Failed
boundary 3	`['a', 'b']`	`['a', 'b']`	Passed
boundary 4	`[]`	`['']`	Failed

SHA-256 / 41b8360e39d4e91bda73eb7f7dac645345be5c8bb51cac432c295697367a03a6

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.split(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('a,b;c'), ['a', 'b', 'c'])
check('boundary 2', solve(',a,'), ['', 'a', ''])
check('boundary 3', solve('a,,b'), ['a', 'b'])
check('boundary 4', solve(''), [''])
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', 'c']`	`['a', 'b', 'c']`	Passed
boundary 2	`['', 'a', '']`	`['', 'a', '']`	Passed
boundary 3	`['a', 'b']`	`['a', 'b']`	Passed
boundary 4	`['']`	`['']`	Passed

SHA-256 / 00bfb53f4185964d5be2c6eb4380cd524a886fcc8ae3f4a200f616e5a4d029e4

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 2026-09-29T14:37:21.353061+00:00.

Case digest / f5a0aeb662846fc7ebd860f8c764b7681270b765a3971b79f469c53304165665