FA-6896 / Content negotiation / Open access
Language selection does not sort quality lexicographically · case 01
Language selection does not sort quality lexicographically.
ROOT CAUSE
The faulty implementation uses `max(qualities,key=lambda p:p[1])[0] if qualities else None` for the language-selection-does-not-sort-quality-lexicographically decision.
VERIFIED REPAIR
Apply the explicit language-selection-does-not-sort-quality-lexicographically contract, including the tested boundary and negative cases.
Unsuccessful approach: The attempted repair uses `min(qualities,key=lambda p:float(p[1]))[0] if qualities else None` and still violates a separate fixture.
Case contract
Bounded offline decision model: language selection does not sort quality lexicographically. Inputs are already validated protocol fields; the explicit fixtures define the supported policy, not a complete protocol implementation.
Why this case matters
This deterministic content negotiation model isolates the language-selection-does-not-sort-quality-lexicographically policy at a network component boundary.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(qualities):
return max(qualities,key=lambda p:p[1])[0] if qualities else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([('en', '0.9'), ('fr', '0.10')]), 'en')", "check('fixture 2', solve([('en', '1'), ('fr', '1.0')]), 'en')", "check('fixture 3', solve([]), None)", "check('fixture 4', solve([('fr', '0.5')]), 'fr')"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
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 2 | fr | en | Failed |
| fixture 3 | None | None | Passed |
| fixture 4 | fr | fr | Passed |
| fixture 1 | en | en | Passed |
SHA-256 / bdc01d860e4c28da32489baa583303b8a320732b0651bb44de37274c138520e4
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(qualities):
return min(qualities,key=lambda p:float(p[1]))[0] if qualities else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([('en', '0.9'), ('fr', '0.10')]), 'en')", "check('fixture 2', solve([('en', '1'), ('fr', '1.0')]), 'en')", "check('fixture 3', solve([]), None)", "check('fixture 4', solve([('fr', '0.5')]), 'fr')"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
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 2 | en | en | Passed |
| fixture 3 | None | None | Passed |
| fixture 4 | fr | fr | Passed |
| fixture 1 | fr | en | Failed |
SHA-256 / 26f1a73fc3fc758293ce87ec8223fd0ecaa749464332211a58964045887e5330
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import ipaddress
import re
from urllib.parse import urlsplit, urljoin
N = 1
observations = []
def solve(qualities):
return max(qualities,key=lambda p:float(p[1]))[0] if qualities else None
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_fixtures = ["check('fixture 1', solve([('en', '0.9'), ('fr', '0.10')]), 'en')", "check('fixture 2', solve([('en', '1'), ('fr', '1.0')]), 'en')", "check('fixture 3', solve([]), None)", "check('fixture 4', solve([('fr', '0.5')]), 'fr')"]
for _line in _fixtures[N % len(_fixtures):] + _fixtures[:N % len(_fixtures)]:
exec(_line)
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 2 | en | en | Passed |
| fixture 3 | None | None | Passed |
| fixture 4 | fr | fr | Passed |
| fixture 1 | en | en | Passed |
SHA-256 / 01f6be5deff3bf0068942f74227b33fa7e8cf599d63bd547729a83fa9f3df55d
Verification & scope
Bounded deterministic policy model over validated inputs; not a complete protocol stack or an interoperability claim. The five variants rotate the same explicit fixture set. 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 2026-09-29T14:38:06.372368+00:00.
Case digest / 379578d5d2e45876d1a39e70820e6dd091d264afa29343bcc279462a91eaef89