FA-2856 / Unicode / Open access

Case folding leaves a decomposed identity · case 01

Case folding leaves a decomposed identity.

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: Return NFC after case folding.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Return NFC after case folding.

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

Case contract

Return NFC after case folding.

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 unicodedata.normalize('NFC',x).casefold()
    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('ǰ'), 'ǰ')
check('boundary 2', solve('Å'), 'å')
check('boundary 3', solve('Straße'), 'strasse')
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	`ǰ`	`ǰ`	Failed
boundary 2	`å`	`å`	Passed
boundary 3	`strasse`	`strasse`	Passed
boundary 4	`x`	`x`	Passed

SHA-256 / 4e93288254cca956d7c05158939748fbb951ecfdb2950674fb66416ad86e48b2

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 x.casefold()
    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('ǰ'), 'ǰ')
check('boundary 2', solve('Å'), 'å')
check('boundary 3', solve('Straße'), 'strasse')
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	`ǰ`	`ǰ`	Failed
boundary 2	`å`	`å`	Failed
boundary 3	`strasse`	`strasse`	Passed
boundary 4	`x`	`x`	Passed

SHA-256 / 6b33d5236b48bcb3c497f5d52d5eb93b3ae9525ea8d1af70a390774374c9373a

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 unicodedata.normalize('NFC',x.casefold())
    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('ǰ'), 'ǰ')
check('boundary 2', solve('Å'), 'å')
check('boundary 3', solve('Straße'), 'strasse')
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	`ǰ`	`ǰ`	Passed
boundary 2	`å`	`å`	Passed
boundary 3	`strasse`	`strasse`	Passed
boundary 4	`x`	`x`	Passed

SHA-256 / c4edf5ddb2a32915dbb93428866d73345e129ec9b49257bdc143b0ce225601a2

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 2026-09-29T14:37:18.020286+00:00.

Case digest / a05498a0d4bf6311a1c6e2258c34fb4263f917bc9b3282568a4fb00cf9da9739