FA-3151 / Serialization / Open access

Nested JSON arrays lose structure · case 01

Nested JSON arrays lose structure.

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: Decode JSON retaining arbitrary list nesting and nulls.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Decode JSON retaining arbitrary list nesting and nulls.

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

Case contract

Decode JSON retaining arbitrary list nesting and nulls.

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 str(x).strip('[]').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('[[1,2],[3]]'), [[1, 2], [3]])
check('boundary 2', solve('[null,[]]'), [None, []])
check('boundary 3', solve('[]'), [])
check('boundary 4', solve('[1]'), [1])
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	`['1', '2]', '[3']`	`[[1, 2], [3]]`	Failed
boundary 2	`['null', '']`	`[None, []]`	Failed
boundary 3	`['']`	`[]`	Failed
boundary 4	`['1']`	`[1]`	Failed

SHA-256 / 5d95fe80262f38918ec4c4af43647a9d3c25f08af6a6e510ab7dfc551b89099f

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 row in json.loads(x) for v in (row if isinstance(row,list) else [row])]
    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]]'), [[1, 2], [3]])
check('boundary 2', solve('[null,[]]'), [None, []])
check('boundary 3', solve('[]'), [])
check('boundary 4', solve('[1]'), [1])
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	`[1, 2, 3]`	`[[1, 2], [3]]`	Failed
boundary 2	`[None]`	`[None, []]`	Failed
boundary 3	`[]`	`[]`	Passed
boundary 4	`[1]`	`[1]`	Passed

SHA-256 / 8bdb4bccc6ee52dcb2f7e469661a8073998a3e79dafeccb52d43855c1f878bd1

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 json.loads(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]]'), [[1, 2], [3]])
check('boundary 2', solve('[null,[]]'), [None, []])
check('boundary 3', solve('[]'), [])
check('boundary 4', solve('[1]'), [1])
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	`[[1, 2], [3]]`	`[[1, 2], [3]]`	Passed
boundary 2	`[None, []]`	`[None, []]`	Passed
boundary 3	`[]`	`[]`	Passed
boundary 4	`[1]`	`[1]`	Passed

SHA-256 / c79afbe0d442505ed763d6f47142b8eb3e4c9637bf9bb6d430f3f103c150246d

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 2026-09-29T14:37:22.138004+00:00.

Case digest / 0a104aba314e3b4f5dae4a5b6ed785b1e6d174819adb4fbc6e14eb7cd2f58819