FA-3186 / Delimited text / Open access

A comma inside a quoted CSV cell becomes a separator · case 01

A comma inside a quoted CSV cell becomes a separator.

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: Read one CSV row using standard double-quote escaping and preserve empty fields.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Read one CSV row using standard double-quote escaping and preserve empty fields.

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

Case contract

Read one CSV row using standard double-quote escaping and preserve 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 x.split(',')
    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""b",x'), ['a"b', 'x'])
check('boundary 3', solve('a,,'), ['a', '', ''])
check('boundary 4', solve('x'), ['x'])
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""b"', 'x']`	`['a"b', 'x']`	Failed
boundary 3	`['a', '', '']`	`['a', '', '']`	Passed
boundary 4	`['x']`	`['x']`	Passed

SHA-256 / e1def41db32aefcfce1dc12f895aa44081d741e38aad9c4eb85c714aa2737116

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.strip('"') for v in x.split(',')]
    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""b",x'), ['a"b', 'x'])
check('boundary 3', solve('a,,'), ['a', '', ''])
check('boundary 4', solve('x'), ['x'])
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""b', 'x']`	`['a"b', 'x']`	Failed
boundary 3	`['a', '', '']`	`['a', '', '']`	Passed
boundary 4	`['x']`	`['x']`	Passed

SHA-256 / 9936b3614588f8a26d0fee451cd225a4afbdace4cd2aef365e4ae87a3bd0db78

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 next(csv.reader([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""b",x'), ['a"b', 'x'])
check('boundary 3', solve('a,,'), ['a', '', ''])
check('boundary 4', solve('x'), ['x'])
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"b', 'x']`	`['a"b', 'x']`	Passed
boundary 3	`['a', '', '']`	`['a', '', '']`	Passed
boundary 4	`['x']`	`['x']`	Passed

SHA-256 / 726fcae7f075151bc62c0f7a72183e0f189693cc0aaa102da8237168734e6692

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 2026-09-29T14:37:22.490945+00:00.

Case digest / a8898dee280d0d6593f15f139034549c8f266b55c4f99b30436abdcaf23ceca0