FA-54011 / Accessibility interaction semantics / Open access
Boolean child offsets become integer indices · case 01
Boolean child offsets become integer indices.
ROOT CAUSE
The start type decision in the child pages adapter violates its declared contract.
THE FAILURE
The start type decision in the child pages adapter violates its declared contract.
Unsuccessful approach: The local repair substitutes not isinstance(start,(int,bool)) but still mishandles the regression fixtures.
Case contract
Input [children,start,count,revision,requested_revision,exposed_ids]. Page accessibility child descriptors in source order, first dedupe IDs then filter exposed IDs. start/count must be nonnegative integers excluding booleans; invalid returns {error:range}. Stale requested revision returns {error:stale} before range checks. Return children slice, total exposed unique count, next offset or None, revision. Zero count yields empty page with next None to avoid nonprogress. Start beyond total gives empty and next None.
Why this case matters
Offline accessibility bridge model with explicit policy; useful for testing semantic API adapters independently of browser implementations.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(data):
children,start,count,revision,requested,exposed = data
if requested != revision: return {'error':'stale'}
if not isinstance(start,int) or type(count) is not int or start < 0 or count < 0: return {'error':'range'}
items = [x for x in dict.fromkeys(children) if x in exposed]
page = items[start:start+count]
nxt = start+len(page) if page and start+len(page) < len(items) else None
return {'children':page,'total':len(items),'next':nxt,'revision':revision}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([['a','hidden','b','a','c'],0,2,N,N,['a','b','c']],), {'children':['a','b'],'total':3,'next':2,'revision':N})
check('contract fixture 2', solve([['a','b','c'],2,4,N,N,['a','b','c']],), {'children':['c'],'total':3,'next':None,'revision':N})
check('contract fixture 3', solve([['a','b'],0,0,N,N,['a','b']],), {'children':[],'total':2,'next':None,'revision':N})
check('contract fixture 4', solve([['a'],-1,2,N,N-1,['a']],), {'error':'stale'})
check('contract fixture 5', solve([['a'],True,1,N,N,['a']],), {'error':'range'})
check('contract fixture 6', solve([['a'],0,False,N,N,['a']],), {'error':'range'})
check('contract fixture 7', solve([['a'],0,-1,N,N,['a']],), {'error':'range'})
check('contract fixture 8', solve([['a'],-1,1,N,N,['a']],), {'error':'range'})
check('contract fixture 9', solve([['a','b','c'],1,1,N,N,['a','b','c']],), {'children':['b'],'total':3,'next':2,'revision':N})
check('contract fixture 10', solve([['a'],N+2,1,N,N,['a']],), {'children':[],'total':1,'next':None,'revision':N})
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 |
|---|---|---|---|
| contract fixture 1 | {'children': ['a', 'b'], 'next': 2, 'revision': 1, 'total': 3} | {'children': ['a', 'b'], 'next': 2, 'revision': 1, 'total': 3} | Passed |
| contract fixture 2 | {'children': ['c'], 'next': None, 'revision': 1, 'total': 3} | {'children': ['c'], 'next': None, 'revision': 1, 'total': 3} | Passed |
| contract fixture 3 | {'children': [], 'next': None, 'revision': 1, 'total': 2} | {'children': [], 'next': None, 'revision': 1, 'total': 2} | Passed |
| contract fixture 4 | {'error': 'stale'} | {'error': 'stale'} | Passed |
| contract fixture 5 | {'children': [], 'next': None, 'revision': 1, 'total': 1} | {'error': 'range'} | Failed |
| contract fixture 6 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 7 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 8 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 9 | {'children': ['b'], 'next': 2, 'revision': 1, 'total': 3} | {'children': ['b'], 'next': 2, 'revision': 1, 'total': 3} | Passed |
| contract fixture 10 | {'children': [], 'next': None, 'revision': 1, 'total': 1} | {'children': [], 'next': None, 'revision': 1, 'total': 1} | Passed |
SHA-256 / b3049b25ab2fc86b8570b1bc8865bbf7d56885672c2c1fd3a47775a76fab41ed
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(data):
children,start,count,revision,requested,exposed = data
if requested != revision: return {'error':'stale'}
if not isinstance(start,(int,bool)) or type(count) is not int or start < 0 or count < 0: return {'error':'range'}
items = [x for x in dict.fromkeys(children) if x in exposed]
page = items[start:start+count]
nxt = start+len(page) if page and start+len(page) < len(items) else None
return {'children':page,'total':len(items),'next':nxt,'revision':revision}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([['a','hidden','b','a','c'],0,2,N,N,['a','b','c']],), {'children':['a','b'],'total':3,'next':2,'revision':N})
check('contract fixture 2', solve([['a','b','c'],2,4,N,N,['a','b','c']],), {'children':['c'],'total':3,'next':None,'revision':N})
check('contract fixture 3', solve([['a','b'],0,0,N,N,['a','b']],), {'children':[],'total':2,'next':None,'revision':N})
check('contract fixture 4', solve([['a'],-1,2,N,N-1,['a']],), {'error':'stale'})
check('contract fixture 5', solve([['a'],True,1,N,N,['a']],), {'error':'range'})
check('contract fixture 6', solve([['a'],0,False,N,N,['a']],), {'error':'range'})
check('contract fixture 7', solve([['a'],0,-1,N,N,['a']],), {'error':'range'})
check('contract fixture 8', solve([['a'],-1,1,N,N,['a']],), {'error':'range'})
check('contract fixture 9', solve([['a','b','c'],1,1,N,N,['a','b','c']],), {'children':['b'],'total':3,'next':2,'revision':N})
check('contract fixture 10', solve([['a'],N+2,1,N,N,['a']],), {'children':[],'total':1,'next':None,'revision':N})
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 |
|---|---|---|---|
| contract fixture 1 | {'children': ['a', 'b'], 'next': 2, 'revision': 1, 'total': 3} | {'children': ['a', 'b'], 'next': 2, 'revision': 1, 'total': 3} | Passed |
| contract fixture 2 | {'children': ['c'], 'next': None, 'revision': 1, 'total': 3} | {'children': ['c'], 'next': None, 'revision': 1, 'total': 3} | Passed |
| contract fixture 3 | {'children': [], 'next': None, 'revision': 1, 'total': 2} | {'children': [], 'next': None, 'revision': 1, 'total': 2} | Passed |
| contract fixture 4 | {'error': 'stale'} | {'error': 'stale'} | Passed |
| contract fixture 5 | {'children': [], 'next': None, 'revision': 1, 'total': 1} | {'error': 'range'} | Failed |
| contract fixture 6 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 7 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 8 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 9 | {'children': ['b'], 'next': 2, 'revision': 1, 'total': 3} | {'children': ['b'], 'next': 2, 'revision': 1, 'total': 3} | Passed |
| contract fixture 10 | {'children': [], 'next': None, 'revision': 1, 'total': 1} | {'children': [], 'next': None, 'revision': 1, 'total': 1} | Passed |
SHA-256 / 820fd2c94854aaafbf748f7e216211e0ee57ce53135bed3af93538b5b7724590
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 10 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
Stipulated finite adapter contract, not a claim of platform accessibility or ARIA conformance. 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 2026-09-29T14:45:44.687755+00:00.
Case digest / e3505460039dd304d61f4498a097ccf7525b96256bb5fd11e6adcda57aea3df0