FAILURE MAP
← Case archive

FA-3201 / Delimited text / Open access

Overflow CSV columns overwrite the final header · case 01

Overflow CSV columns overwrite the final header.

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 two-column a,b CSV as a dictionary, storing overflow cells under extra and missing b as None.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Read two-column a,b CSV as a dictionary, storing overflow cells under extra and missing b as None.

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

Case contract

Read two-column a,b CSV as a dictionary, storing overflow cells under extra and missing b as None.

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 dict(zip(['a','b'],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('1,2,3'), {'a': '1', 'b': '2', 'extra': ['3']})
check('boundary 2', solve('1'), {'a': '1', 'b': None})
check('boundary 3', solve('1,'), {'a': '1', 'b': ''})
check('boundary 4', solve('1,2'), {'a': '1', 'b': '2'})
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 fixtureActualExpectedOutcome
boundary 1{'a': '1', 'b': '2'}{'a': '1', 'b': '2', 'extra': ['3']}Failed
boundary 2{'a': '1'}{'a': '1', 'b': None}Failed
boundary 3{'a': '1', 'b': ''}{'a': '1', 'b': ''}Passed
boundary 4{'a': '1', 'b': '2'}{'a': '1', 'b': '2'}Passed

SHA-256 / 553b117d6ae8aacb1bd0ac072cc071908664fca1f421889f63dfcd88a9e5f1b4

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 dict(zip(['a','b'],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('1,2,3'), {'a': '1', 'b': '2', 'extra': ['3']})
check('boundary 2', solve('1'), {'a': '1', 'b': None})
check('boundary 3', solve('1,'), {'a': '1', 'b': ''})
check('boundary 4', solve('1,2'), {'a': '1', 'b': '2'})
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 fixtureActualExpectedOutcome
boundary 1{'a': '1', 'b': '2'}{'a': '1', 'b': '2', 'extra': ['3']}Failed
boundary 2{'a': '1', 'b': ''}{'a': '1', 'b': None}Failed
boundary 3{'a': '1', 'b': ''}{'a': '1', 'b': ''}Passed
boundary 4{'a': '1', 'b': '2'}{'a': '1', 'b': '2'}Passed

SHA-256 / 0c45c6462c1d38156262ca85606422f6d373b30508b8742952f1ec1e3cd2ac57

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.DictReader([x],fieldnames=['a','b'],restkey='extra',restval=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('1,2,3'), {'a': '1', 'b': '2', 'extra': ['3']})
check('boundary 2', solve('1'), {'a': '1', 'b': None})
check('boundary 3', solve('1,'), {'a': '1', 'b': ''})
check('boundary 4', solve('1,2'), {'a': '1', 'b': '2'})
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 fixtureActualExpectedOutcome
boundary 1{'a': '1', 'b': '2', 'extra': ['3']}{'a': '1', 'b': '2', 'extra': ['3']}Passed
boundary 2{'a': '1', 'b': None}{'a': '1', 'b': None}Passed
boundary 3{'a': '1', 'b': ''}{'a': '1', 'b': ''}Passed
boundary 4{'a': '1', 'b': '2'}{'a': '1', 'b': '2'}Passed

SHA-256 / 5ca4c20a4b2097ebe0d8c3a06013e40d378c19595de8cb5b41f54e91ac20aedc

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 2026-09-29T14:37:22.552468+00:00.

Case digest / 0ba1b8157e522598712cfb985cd6d9e5c3eb3afbfd8b706d9e5ec8d030e75514