FA-3016 / Text processing / Open access

Tabs expand without considering current column · case 01

Tabs expand without considering current column.

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: Expand tabs to tab stops of width four, resetting column at line boundaries.

VERIFIED REPAIR

Implement the complete stated contract, including the boundary fixtures: Expand tabs to tab stops of width four, resetting column at line boundaries.

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

Case contract

Expand tabs to tab stops of width four, resetting column at line boundaries.

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.replace('\x09','    ')
    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('a\tb'), 'a   b')
check('boundary 2', solve('\t\tx'), '        x')
check('boundary 3', solve('abc\n\tx'), 'abc\n    x')
check('boundary 4', solve('abcd\t'), 'abcd    ')
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	`a b`	`a b`	Failed
boundary 2	`x`	`x`	Passed
boundary 3	`abc x`	`abc x`	Passed
boundary 4	`abcd`	`abcd`	Passed

SHA-256 / b289f3a5304fa1c9b47f6e5b1e0ffc8399ac5b9d9ccaba2225761bf3ff36450d

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 ''.join(' '*(4-i%4) if c=='\x09' else c for i,c in enumerate(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('a\tb'), 'a   b')
check('boundary 2', solve('\t\tx'), '        x')
check('boundary 3', solve('abc\n\tx'), 'abc\n    x')
check('boundary 4', solve('abcd\t'), 'abcd    ')
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	`a b`	`a b`	Passed
boundary 2	`x`	`x`	Failed
boundary 3	`abc x`	`abc x`	Passed
boundary 4	`abcd`	`abcd`	Passed

SHA-256 / 4e46fdbee1354db642a5755cdfe09cea52a12316da2a7f49a8eca112c1cc96e7

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 x.expandtabs(4)
    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('a\tb'), 'a   b')
check('boundary 2', solve('\t\tx'), '        x')
check('boundary 3', solve('abc\n\tx'), 'abc\n    x')
check('boundary 4', solve('abcd\t'), 'abcd    ')
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	`a b`	`a b`	Passed
boundary 2	`x`	`x`	Passed
boundary 3	`abc x`	`abc x`	Passed
boundary 4	`abcd`	`abcd`	Passed

SHA-256 / 6c0d28d7f90f209a720f8628d11d98a5a53b8f388cc034714b8aff7946f69376

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 2026-09-29T14:37:20.461221+00:00.

Case digest / c2dcb6e0bc45e5a50596eb97934b5a44ede09708cecfe1c44c7cf6b674213e8b