FA-9766 / Configuration / Open access

Configuration provenance tracking: Later values retain their previous assignment · case 01

Later values retain their previous assignment.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The implementation substitutes values.setdefault(key, value) for values[key] = value, so later values retain their previous assignment.

VERIFIED REPAIR

Replace present values even if false.

Unsuccessful approach: The attempted repair substitutes values[key] = value or values.get(key). Fixture 6 still yields ({'a': 1}, {'a': 'user'}) instead of ({'a': False}, {'a': 'user'}).

Case contract

Return final values and source names. Each present setting replaces prior value and provenance, deletions remove both, and layers with no assignment preserve provenance.

Why this case matters

An offline model of configuration provenance tracking, suitable for testing build and release tooling without external services.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(layers):
    values = {}
    sources = {}
    for source, settings in layers:
        for key, value in settings.items():
            if value is None:
                values.pop(key, None)
                sources.pop(key, None)
            else:
                values.setdefault(key, value)
                sources[key] = source
    return (values, sources)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve([]), ({}, {}))
check('fixture 2', solve([('default', {'a': 1}), ('user', {'a': 2})]), ({'a': 2}, {'a': 'user'}))
check('fixture 3', solve([('default', {'a': 1}), ('user', {'a': None})]), ({}, {}))
check('fixture 4', solve([('default', {'a': 1}), ('user', {})]), ({'a': 1}, {'a': 'default'}))
check('fixture 5', solve([('default', {'a': 1}), ('user', {'a': 1})]), ({'a': 1}, {'a': 'user'}))
check('fixture 6', solve([('default', {'a': 1}), ('user', {'a': False})]), ({'a': False}, {'a': 'user'}))
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
fixture 1	`[{}, {}]`	`[{}, {}]`	Passed
fixture 2	`[{'a': 1}, {'a': 'user'}]`	`[{'a': 2}, {'a': 'user'}]`	Failed
fixture 3	`[{}, {}]`	`[{}, {}]`	Passed
fixture 4	`[{'a': 1}, {'a': 'default'}]`	`[{'a': 1}, {'a': 'default'}]`	Passed
fixture 5	`[{'a': 1}, {'a': 'user'}]`	`[{'a': 1}, {'a': 'user'}]`	Passed
fixture 6	`[{'a': 1}, {'a': 'user'}]`	`[{'a': False}, {'a': 'user'}]`	Failed

SHA-256 / 30991829e88d4ccff83cd9f5bb6cd1ae6c684b8375c2e587f30934a6db8dbb73

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(layers):
    values = {}
    sources = {}
    for source, settings in layers:
        for key, value in settings.items():
            if value is None:
                values.pop(key, None)
                sources.pop(key, None)
            else:
                values[key] = value or values.get(key)
                sources[key] = source
    return (values, sources)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve([]), ({}, {}))
check('fixture 2', solve([('default', {'a': 1}), ('user', {'a': 2})]), ({'a': 2}, {'a': 'user'}))
check('fixture 3', solve([('default', {'a': 1}), ('user', {'a': None})]), ({}, {}))
check('fixture 4', solve([('default', {'a': 1}), ('user', {})]), ({'a': 1}, {'a': 'default'}))
check('fixture 5', solve([('default', {'a': 1}), ('user', {'a': 1})]), ({'a': 1}, {'a': 'user'}))
check('fixture 6', solve([('default', {'a': 1}), ('user', {'a': False})]), ({'a': False}, {'a': 'user'}))
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
fixture 1	`[{}, {}]`	`[{}, {}]`	Passed
fixture 2	`[{'a': 2}, {'a': 'user'}]`	`[{'a': 2}, {'a': 'user'}]`	Passed
fixture 3	`[{}, {}]`	`[{}, {}]`	Passed
fixture 4	`[{'a': 1}, {'a': 'default'}]`	`[{'a': 1}, {'a': 'default'}]`	Passed
fixture 5	`[{'a': 1}, {'a': 'user'}]`	`[{'a': 1}, {'a': 'user'}]`	Passed
fixture 6	`[{'a': 1}, {'a': 'user'}]`	`[{'a': False}, {'a': 'user'}]`	Failed

SHA-256 / 8fffa8decd38d1b03ebc1e6ea5a2a46961473911732c1061e9fac41a2839914a

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(layers):
    values = {}
    sources = {}
    for source, settings in layers:
        for key, value in settings.items():
            if value is None:
                values.pop(key, None)
                sources.pop(key, None)
            else:
                values[key] = value
                sources[key] = source
    return (values, sources)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve([]), ({}, {}))
check('fixture 2', solve([('default', {'a': 1}), ('user', {'a': 2})]), ({'a': 2}, {'a': 'user'}))
check('fixture 3', solve([('default', {'a': 1}), ('user', {'a': None})]), ({}, {}))
check('fixture 4', solve([('default', {'a': 1}), ('user', {})]), ({'a': 1}, {'a': 'default'}))
check('fixture 5', solve([('default', {'a': 1}), ('user', {'a': 1})]), ({'a': 1}, {'a': 'user'}))
check('fixture 6', solve([('default', {'a': 1}), ('user', {'a': False})]), ({'a': False}, {'a': 'user'}))
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
fixture 1	`[{}, {}]`	`[{}, {}]`	Passed
fixture 2	`[{'a': 2}, {'a': 'user'}]`	`[{'a': 2}, {'a': 'user'}]`	Passed
fixture 3	`[{}, {}]`	`[{}, {}]`	Passed
fixture 4	`[{'a': 1}, {'a': 'default'}]`	`[{'a': 1}, {'a': 'default'}]`	Passed
fixture 5	`[{'a': 1}, {'a': 'user'}]`	`[{'a': 1}, {'a': 'user'}]`	Passed
fixture 6	`[{'a': False}, {'a': 'user'}]`	`[{'a': False}, {'a': 'user'}]`	Passed

SHA-256 / 6a5216a91f6fe858255bf6db7fcebed36972b36d0748dee95d89b90368ea1633

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 2026-09-29T14:38:32.926166+00:00.

Case digest / 97456279c38dbf48c7fa771e594625e45bb3aaddadc425ca21e23f8270194718