FA-54016 / Accessibility interaction semantics / Open access
Boolean page capacities are treated as a one-child request · case 01
Boolean page capacities are treated as a one-child request.
ROOT CAUSE
The count type decision in the child pages adapter violates its declared contract.
VERIFIED REPAIR
Apply the exact contract at the count type decision: type(count) is not int
Unsuccessful approach: The local repair substitutes not isinstance(count,(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 type(start) is not int or not isinstance(count,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 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 6 | {'children': [], 'next': None, 'revision': 1, 'total': 1} | {'error': 'range'} | Failed |
| 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 / 6b139dee32eabb3a93518b5f252d7a0f9d0be3dd5af46f5bec674a2c9a132c58
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 type(start) is not int or not isinstance(count,(int,bool)) 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 | {'error': 'range'} | {'error': 'range'} | Passed |
| contract fixture 6 | {'children': [], 'next': None, 'revision': 1, 'total': 1} | {'error': 'range'} | Failed |
| 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 / 74420b6cacfe9a320c33d09c2c47b4ef0534ad5946cbf5c303eb24a63a6fa8d0
3 / The verified repair
Exit 0"""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 type(start) is not 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 | {'error': 'range'} | {'error': 'range'} | Passed |
| 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 / 20df8118bdcae1b7f2289293c8fb880daa29a315f4b40dc04357ca9a3102780a
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 2026-09-29T14:45:44.465579+00:00.
Case digest / e87de8c96c748f33ffae6e3a49decdc5ce6488160db07a5b5c184c8f061f94f3