FA-4566 / Iterator consumption / Open access
Groupby adjacency not global key · case 01
The operation returns a result or retained state that violates this contract: Group consecutive equal values into [key,group] pairs; separated equal runs remain separate.
ROOT CAUSE
Global key grouping merges separate adjacent runs with the same key.
VERIFIED REPAIR
Group consecutive equal values into [key,group] pairs; separated equal runs remain separate.
Unsuccessful approach: Sorting first changes run order and merges separated runs.
Case contract
Group consecutive equal values into [key,group] pairs; separated equal runs remain separate. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.
Why this case matters
A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import itertools as it
from collections import deque
N = 1
observations = []
def solve(x, y=None):
return [[k,[v for v in x if v==k]] for k in dict.fromkeys(x)]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('separate equal runs', solve(['a', 'b', 'a']), [['a', ['a']], ['b', ['b']], ['a', ['a']]])
check('same run', solve(['a', 'a']), [['a', ['a', 'a']]])
check('empty', solve([]), [])
check('nonlexical runs', solve(['b', 'b', 'a']), [['b', ['b', 'b']], ['a', ['a']]])
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 |
|---|---|---|---|
| separate equal runs | [['a', ['a', 'a']], ['b', ['b']]] | [['a', ['a']], ['b', ['b']], ['a', ['a']]] | Failed |
| same run | [['a', ['a', 'a']]] | [['a', ['a', 'a']]] | Passed |
| empty | [] | [] | Passed |
| nonlexical runs | [['b', ['b', 'b']], ['a', ['a']]] | [['b', ['b', 'b']], ['a', ['a']]] | Passed |
SHA-256 / e3f594f64e5e2768af81025c2deb675c3ff96ac1243249e3cb3ef7814e478a35
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import itertools as it
from collections import deque
N = 1
observations = []
def solve(x, y=None):
return [[k,list(g)] for k,g in it.groupby(sorted(x))]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('separate equal runs', solve(['a', 'b', 'a']), [['a', ['a']], ['b', ['b']], ['a', ['a']]])
check('same run', solve(['a', 'a']), [['a', ['a', 'a']]])
check('empty', solve([]), [])
check('nonlexical runs', solve(['b', 'b', 'a']), [['b', ['b', 'b']], ['a', ['a']]])
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 |
|---|---|---|---|
| separate equal runs | [['a', ['a', 'a']], ['b', ['b']]] | [['a', ['a']], ['b', ['b']], ['a', ['a']]] | Failed |
| same run | [['a', ['a', 'a']]] | [['a', ['a', 'a']]] | Passed |
| empty | [] | [] | Passed |
| nonlexical runs | [['a', ['a']], ['b', ['b', 'b']]] | [['b', ['b', 'b']], ['a', ['a']]] | Failed |
SHA-256 / 2600f5018aeb9d7ee35e466d9eb69c2fe013789ead8a71e8de0d4c3d06939a77
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import itertools as it
from collections import deque
N = 1
observations = []
def solve(x, y=None):
return [[k,list(g)] for k,g in it.groupby(x)]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('separate equal runs', solve(['a', 'b', 'a']), [['a', ['a']], ['b', ['b']], ['a', ['a']]])
check('same run', solve(['a', 'a']), [['a', ['a', 'a']]])
check('empty', solve([]), [])
check('nonlexical runs', solve(['b', 'b', 'a']), [['b', ['b', 'b']], ['a', ['a']]])
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 |
|---|---|---|---|
| separate equal runs | [['a', ['a']], ['b', ['b']], ['a', ['a']]] | [['a', ['a']], ['b', ['b']], ['a', ['a']]] | Passed |
| same run | [['a', ['a', 'a']]] | [['a', ['a', 'a']]] | Passed |
| empty | [] | [] | Passed |
| nonlexical runs | [['b', ['b', 'b']], ['a', ['a']]] | [['b', ['b', 'b']], ['a', ['a']]] | Passed |
SHA-256 / f87a0df2d0bc25cb955717e1b9ee9120a0fb15cf62bbc8417dc387ca9ba60464
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 2026-09-29T14:37:40.569835+00:00.
Case digest / 23ab10db08177b660acb1ce37cb85ffc3eeac297ad83e4c37149dfce18f3603a