FA-3831 / Serialization / Open access

String precision pads rather than truncates · case 01

String precision pads rather than truncates.

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: Format text to at most three codepoints without width padding.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Format text to at most three codepoints without width padding.

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

Case contract

Format text to at most three codepoints without width padding.

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.ljust(3)
    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('abcdef'), 'abc')
check('boundary 2', solve('a'), 'a')
check('boundary 3', solve('😀abx'), '😀ab')
check('boundary 4', solve(''), '')
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	`abcdef`	`abc`	Failed
boundary 2	`a`	`a`	Failed
boundary 3	`😀abx`	`😀ab`	Failed
boundary 4			Failed

SHA-256 / 7670432302f97c9340651b5450eadeb144c0ee3e345868a5777631479eca7abd

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[:3].ljust(3)
    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('abcdef'), 'abc')
check('boundary 2', solve('a'), 'a')
check('boundary 3', solve('😀abx'), '😀ab')
check('boundary 4', solve(''), '')
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	`abc`	`abc`	Passed
boundary 2	`a`	`a`	Failed
boundary 3	`😀ab`	`😀ab`	Passed
boundary 4			Failed

SHA-256 / 836b4692b96f28ddd53fed37bf22d947f0d67a5d697430ad1985262f6b6f361f

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 '{:.3}'.format(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('abcdef'), 'abc')
check('boundary 2', solve('a'), 'a')
check('boundary 3', solve('😀abx'), '😀ab')
check('boundary 4', solve(''), '')
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	`abc`	`abc`	Passed
boundary 2	`a`	`a`	Passed
boundary 3	`😀ab`	`😀ab`	Passed
boundary 4			Passed

SHA-256 / ccea1b84bae1ae10d5e2f32c9a0772476d0b264bccfeb8fb5c6a0b7753d80cd4

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 2026-09-29T14:37:31.435984+00:00.

Case digest / 3eaec1af355cb8e39a2c387e1fc99a7a504b70bdcb55b6a2910ed53254befbd3