FA-9501 / Dependency resolution / Open access
Package source selection: Last source declaration overrides precedence · case 01
Last source declaration overrides precedence.
ROOT CAUSE
The implementation substitutes choices[-1]['name'] for choices[0]['name'], so last source declaration overrides precedence.
THE FAILURE
The implementation substitutes choices[-1]['name'] for choices[0]['name'], so last source declaration overrides precedence.
Unsuccessful approach: The attempted repair substitutes sorted(s['name'] for s in choices)[-1]. Fixture 2 still yields 'last' instead of 'first'.
Case contract
Return first declared trusted nonmirror source containing the package, otherwise first trusted mirror containing it. Disabled and untrusted sources never participate.
Why this case matters
An offline model of package source selection, 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(name, sources):
eligible = [s for s in sources if s['enabled']]
eligible = [s for s in eligible if s['trusted']]
eligible = [s for s in eligible if name in s['packages']]
primary = [s for s in eligible if not s['mirror']]
choices = primary or eligible
return choices[-1]['name'] if choices else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('a', []), None)
check('fixture 2', solve('a', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}, {'name': 'bad', 'enabled': False, 'trusted': True, 'packages': ['a'], 'mirror': False}, {'name': 'untrusted', 'enabled': True, 'trusted': False, 'packages': ['a'], 'mirror': False}, {'name': 'first', 'enabled': True, 'trusted': True, 'packages': ['a', 'b'], 'mirror': False}, {'name': 'last', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': False}]), 'first')
check('fixture 3', solve('a', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}]), 'mirror')
check('fixture 4', solve('b', []), None)
check('fixture 5', solve('b', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}, {'name': 'bad', 'enabled': False, 'trusted': True, 'packages': ['a'], 'mirror': False}, {'name': 'untrusted', 'enabled': True, 'trusted': False, 'packages': ['a'], 'mirror': False}, {'name': 'first', 'enabled': True, 'trusted': True, 'packages': ['a', 'b'], 'mirror': False}, {'name': 'last', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': False}]), 'first')
check('fixture 6', solve('b', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}]), None)
check('fixture 7', solve('missing', []), None)
check('fixture 8', solve('missing', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}, {'name': 'bad', 'enabled': False, 'trusted': True, 'packages': ['a'], 'mirror': False}, {'name': 'untrusted', 'enabled': True, 'trusted': False, 'packages': ['a'], 'mirror': False}, {'name': 'first', 'enabled': True, 'trusted': True, 'packages': ['a', 'b'], 'mirror': False}, {'name': 'last', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': False}]), None)
check('fixture 9', solve('missing', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}]), None)
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 | None | None | Passed |
| fixture 2 | last | first | Failed |
| fixture 3 | mirror | mirror | Passed |
| fixture 4 | None | None | Passed |
| fixture 5 | first | first | Passed |
| fixture 6 | None | None | Passed |
| fixture 7 | None | None | Passed |
| fixture 8 | None | None | Passed |
| fixture 9 | None | None | Passed |
SHA-256 / 238561b798b7940e95b9c7788f040c1600377d8836f8e98702c4d62a0320a231
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(name, sources):
eligible = [s for s in sources if s['enabled']]
eligible = [s for s in eligible if s['trusted']]
eligible = [s for s in eligible if name in s['packages']]
primary = [s for s in eligible if not s['mirror']]
choices = primary or eligible
return sorted(s['name'] for s in choices)[-1] if choices else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve('a', []), None)
check('fixture 2', solve('a', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}, {'name': 'bad', 'enabled': False, 'trusted': True, 'packages': ['a'], 'mirror': False}, {'name': 'untrusted', 'enabled': True, 'trusted': False, 'packages': ['a'], 'mirror': False}, {'name': 'first', 'enabled': True, 'trusted': True, 'packages': ['a', 'b'], 'mirror': False}, {'name': 'last', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': False}]), 'first')
check('fixture 3', solve('a', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}]), 'mirror')
check('fixture 4', solve('b', []), None)
check('fixture 5', solve('b', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}, {'name': 'bad', 'enabled': False, 'trusted': True, 'packages': ['a'], 'mirror': False}, {'name': 'untrusted', 'enabled': True, 'trusted': False, 'packages': ['a'], 'mirror': False}, {'name': 'first', 'enabled': True, 'trusted': True, 'packages': ['a', 'b'], 'mirror': False}, {'name': 'last', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': False}]), 'first')
check('fixture 6', solve('b', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}]), None)
check('fixture 7', solve('missing', []), None)
check('fixture 8', solve('missing', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}, {'name': 'bad', 'enabled': False, 'trusted': True, 'packages': ['a'], 'mirror': False}, {'name': 'untrusted', 'enabled': True, 'trusted': False, 'packages': ['a'], 'mirror': False}, {'name': 'first', 'enabled': True, 'trusted': True, 'packages': ['a', 'b'], 'mirror': False}, {'name': 'last', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': False}]), None)
check('fixture 9', solve('missing', [{'name': 'mirror', 'enabled': True, 'trusted': True, 'packages': ['a'], 'mirror': True}]), None)
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 | None | None | Passed |
| fixture 2 | last | first | Failed |
| fixture 3 | mirror | mirror | Passed |
| fixture 4 | None | None | Passed |
| fixture 5 | first | first | Passed |
| fixture 6 | None | None | Passed |
| fixture 7 | None | None | Passed |
| fixture 8 | None | None | Passed |
| fixture 9 | None | None | Passed |
SHA-256 / affe11ebbe068e2ab1b7f1c16476a8b2d386cebbf136db6ec12f2774c41a7b31
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 9 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.
Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.
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Sign in to the archive ↗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 2026-09-29T14:38:30.411794+00:00.
Case digest / f854662df7b8ce708c90bab91af13f3fb7f679f2ac7fbde4d93c99831986464b