FA-3281 / Encodings / Open access

Percent decoding destroys non-UTF8 bytes · case 01

Percent decoding destroys non-UTF8 bytes.

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 percent escapes to raw integer bytes, UTF-8-encoding unescaped Unicode text.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Decode percent escapes to raw integer bytes, UTF-8-encoding unescaped Unicode text.

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

Case contract

Decode percent escapes to raw integer bytes, UTF-8-encoding unescaped Unicode text.

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 list(unquote(x).encode('utf-8'))
    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('%FF'), [255])
check('boundary 2', solve('é'), [195, 169])
check('boundary 3', solve('%00'), [0])
check('boundary 4', solve('%ZZ'), [37, 90, 90])
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	`[239, 191, 189]`	`[255]`	Failed
boundary 2	`[195, 169]`	`[195, 169]`	Passed
boundary 3	`[0]`	`[0]`	Passed
boundary 4	`[37, 90, 90]`	`[37, 90, 90]`	Passed

SHA-256 / 2f19fb1ed714cb43fad224cdf92a912f0012670efe8a2888313edeaaed307ce8

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 list(x.encode('utf-8'))
    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('%FF'), [255])
check('boundary 2', solve('é'), [195, 169])
check('boundary 3', solve('%00'), [0])
check('boundary 4', solve('%ZZ'), [37, 90, 90])
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	`[37, 70, 70]`	`[255]`	Failed
boundary 2	`[195, 169]`	`[195, 169]`	Passed
boundary 3	`[37, 48, 48]`	`[0]`	Failed
boundary 4	`[37, 90, 90]`	`[37, 90, 90]`	Passed

SHA-256 / 44d5257797362ce1437b92d211f5f40be3ac74e2c7d9d8cc7f917c3f952a3c07

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 list(unquote_to_bytes(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('%FF'), [255])
check('boundary 2', solve('é'), [195, 169])
check('boundary 3', solve('%00'), [0])
check('boundary 4', solve('%ZZ'), [37, 90, 90])
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	`[255]`	`[255]`	Passed
boundary 2	`[195, 169]`	`[195, 169]`	Passed
boundary 3	`[0]`	`[0]`	Passed
boundary 4	`[37, 90, 90]`	`[37, 90, 90]`	Passed

SHA-256 / 7a2678f52ec0bd1f230c9106793b2f86bc8d08496db6c168a79bafa92480040a

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 2026-09-29T14:37:23.574496+00:00.

Case digest / 1b7ef799f0e45c5c0d34c4d31b37c217868683b4490a96ab6e8776eac64643e9