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FA-5136 / Context managers / Open access

Context exception suppression: Discards the truthy __exit__ decision and propagates ValueError · case 01

Discards the truthy __exit__ decision and propagates ValueError and changes the required Python-language result.

Verified by executionVariant 1 · 5 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Discards the truthy __exit__ decision and propagates ValueError. The executable reproducer isolates this operation from the rest of the contract.

VERIFIED REPAIR

A context manager suppresses only ValueError when enabled. __exit__ observes the actual exception class or None on normal exit; unsuppressed exceptions reach the outer handler and skip after.

Unsuccessful approach: The alternative still fails because it suppresses ValueError even when the policy is disabled.

Case contract

A context manager suppresses only ValueError when enabled. __exit__ observes the actual exception class or None on normal exit; unsuppressed exceptions reach the outer handler and skip after. Inputs use the finite Python types shown in the fixtures. An error string denotes the specified caught exception, not an unhandled process failure.

Why this case matters

Runs Python standard-library language operations in a deterministic local reproducer. Literal expected answers are authored independently. Related defects share an evaluation group to avoid benchmark split leakage.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(error, enabled):
    log=[]
    class Manager:
        def __enter__(self):
            log.append('enter')
            return self
        def __exit__(self, typ, exc, tb):
            log.append('exit:'+('none' if typ is None else typ.__name__))
            return False
    try:
        with Manager():
            log.append('body')
            if error=='value': raise ValueError('value')
            if error=='key': raise KeyError('key')
            if error=='type': raise TypeError('type')
        log.append('after')
    except Exception as exc:
        log.append('caught:'+type(exc).__name__)
    return log
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('normal exit', solve('none', True), ['enter', 'body', 'exit:none', 'after'])
check('selected error suppressed', solve('value', True), ['enter', 'body', 'exit:ValueError', 'after'])
check('disabled propagation', solve('value', False), ['enter', 'body', 'exit:ValueError', 'caught:ValueError'])
check('unrelated error propagates', solve('key', True), ['enter', 'body', 'exit:KeyError', 'caught:KeyError'])
check('other unrelated type', solve('type', True), ['enter', 'body', 'exit:TypeError', 'caught:TypeError'])
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 fixtureActualExpectedOutcome
normal exit['enter', 'body', 'exit:none', 'after']['enter', 'body', 'exit:none', 'after']Passed
selected error suppressed['enter', 'body', 'exit:ValueError', 'caught:ValueError']['enter', 'body', 'exit:ValueError', 'after']Failed
disabled propagation['enter', 'body', 'exit:ValueError', 'caught:ValueError']['enter', 'body', 'exit:ValueError', 'caught:ValueError']Passed
unrelated error propagates['enter', 'body', 'exit:KeyError', 'caught:KeyError']['enter', 'body', 'exit:KeyError', 'caught:KeyError']Passed
other unrelated type['enter', 'body', 'exit:TypeError', 'caught:TypeError']['enter', 'body', 'exit:TypeError', 'caught:TypeError']Passed

SHA-256 / f7b05733326cc9137c0c1d7c65d636e88597f2eec8c19b780597de98a6a5e349

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(error, enabled):
    log=[]
    class Manager:
        def __enter__(self):
            log.append('enter')
            return self
        def __exit__(self, typ, exc, tb):
            log.append('exit:'+('none' if typ is None else typ.__name__))
            return typ is ValueError
    try:
        with Manager():
            log.append('body')
            if error=='value': raise ValueError('value')
            if error=='key': raise KeyError('key')
            if error=='type': raise TypeError('type')
        log.append('after')
    except Exception as exc:
        log.append('caught:'+type(exc).__name__)
    return log
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('normal exit', solve('none', True), ['enter', 'body', 'exit:none', 'after'])
check('selected error suppressed', solve('value', True), ['enter', 'body', 'exit:ValueError', 'after'])
check('disabled propagation', solve('value', False), ['enter', 'body', 'exit:ValueError', 'caught:ValueError'])
check('unrelated error propagates', solve('key', True), ['enter', 'body', 'exit:KeyError', 'caught:KeyError'])
check('other unrelated type', solve('type', True), ['enter', 'body', 'exit:TypeError', 'caught:TypeError'])
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 fixtureActualExpectedOutcome
normal exit['enter', 'body', 'exit:none', 'after']['enter', 'body', 'exit:none', 'after']Passed
selected error suppressed['enter', 'body', 'exit:ValueError', 'after']['enter', 'body', 'exit:ValueError', 'after']Passed
disabled propagation['enter', 'body', 'exit:ValueError', 'after']['enter', 'body', 'exit:ValueError', 'caught:ValueError']Failed
unrelated error propagates['enter', 'body', 'exit:KeyError', 'caught:KeyError']['enter', 'body', 'exit:KeyError', 'caught:KeyError']Passed
other unrelated type['enter', 'body', 'exit:TypeError', 'caught:TypeError']['enter', 'body', 'exit:TypeError', 'caught:TypeError']Passed

SHA-256 / 13f503211282da046e42b6d88dae8b6bab7b377d13143c436ba23d5a8a15ad17

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(error, enabled):
    log=[]
    class Manager:
        def __enter__(self):
            log.append('enter')
            return self
        def __exit__(self, typ, exc, tb):
            log.append('exit:'+('none' if typ is None else typ.__name__))
            return typ is ValueError and enabled
    try:
        with Manager():
            log.append('body')
            if error=='value': raise ValueError('value')
            if error=='key': raise KeyError('key')
            if error=='type': raise TypeError('type')
        log.append('after')
    except Exception as exc:
        log.append('caught:'+type(exc).__name__)
    return log
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('normal exit', solve('none', True), ['enter', 'body', 'exit:none', 'after'])
check('selected error suppressed', solve('value', True), ['enter', 'body', 'exit:ValueError', 'after'])
check('disabled propagation', solve('value', False), ['enter', 'body', 'exit:ValueError', 'caught:ValueError'])
check('unrelated error propagates', solve('key', True), ['enter', 'body', 'exit:KeyError', 'caught:KeyError'])
check('other unrelated type', solve('type', True), ['enter', 'body', 'exit:TypeError', 'caught:TypeError'])
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 fixtureActualExpectedOutcome
normal exit['enter', 'body', 'exit:none', 'after']['enter', 'body', 'exit:none', 'after']Passed
selected error suppressed['enter', 'body', 'exit:ValueError', 'after']['enter', 'body', 'exit:ValueError', 'after']Passed
disabled propagation['enter', 'body', 'exit:ValueError', 'caught:ValueError']['enter', 'body', 'exit:ValueError', 'caught:ValueError']Passed
unrelated error propagates['enter', 'body', 'exit:KeyError', 'caught:KeyError']['enter', 'body', 'exit:KeyError', 'caught:KeyError']Passed
other unrelated type['enter', 'body', 'exit:TypeError', 'caught:TypeError']['enter', 'body', 'exit:TypeError', 'caught:TypeError']Passed

SHA-256 / 28bc3eb1a5f50a36a2e2c15669ed1394b41285c80e1d21dfd5ce2359cd5baecb

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 2026-09-29T14:37:46.462454+00:00.

Case digest / 80304b447d283cc3853225e2d9b6cc0b4d4eeb1ea38b050bce7c4197ea9f5200