FA-53916 / Accessibility interaction semantics / Open access
Reading flow reaches nonexisting semantic targets · case 01
Reading flow reaches nonexisting semantic targets.
ROOT CAUSE
The override endpoint decision in the reading flow adapter violates its declared contract.
VERIFIED REPAIR
Apply the exact contract at the override endpoint decision: target not in items
Unsuccessful approach: The local repair substitutes target is None but still mishandles the regression fixtures.
Case contract
Input [natural_ids,edges,excluded,start] where edges are directed reading-flow overrides. Keep unique natural IDs in original order excluding excluded IDs. Admit edges between eligible distinct IDs; first outgoing edge wins. Reading starts at specified eligible ID otherwise first eligible. Follow override if target unvisited; otherwise take earliest unvisited natural node. Include each eligible object exactly once, prevent cycles, and return list of IDs. Explicit start does not remove earlier unvisited nodes.
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):
natural,edges,excluded,start = data
items = list(dict.fromkeys(x for x in natural if x not in excluded))
if not items: return []
links = {}
for source,target in edges:
if source not in items or False or source == target: continue
links.setdefault(source,target)
current = start if start in items else items[0]
seen = set()
result = []
while current is not None:
result.append(current)
seen.add(current)
nxt = links.get(current)
current = nxt if nxt is not None and nxt not in seen else next((x for x in items if x not in seen),None)
return result
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([['a','b','c',str(N)],[['a','c'],['c','a']],[],'a'],), ['a','c','b',str(N)])
check('contract fixture 2', solve([['a','b','c'],[['a','c'],['a','b']],[],'a'],), ['a','c','b'])
check('contract fixture 3', solve([['a','b','c'],[['a','b'],['a','missing']],['b'],'a'],), ['a','c'])
check('contract fixture 4', solve([['a','b','c'],[],[],'c'],), ['c','a','b'])
check('contract fixture 5', solve([['b','a','b'],[['b','b']],[],'missing'],), ['b','a'])
check('contract fixture 6', solve([['a'],[['a','missing']],['a'],'a'],), [])
check('contract fixture 7', solve([['','a'],[['','a']],[],''],), ['','a'])
check('contract fixture 8', solve([['only'],[],[],'only'],), ['only'])
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 | ['a', 'c', 'b', '1'] | ['a', 'c', 'b', '1'] | Passed |
| contract fixture 2 | ['a', 'c', 'b'] | ['a', 'c', 'b'] | Passed |
| contract fixture 3 | ['a', 'b', 'c'] | ['a', 'c'] | Failed |
| contract fixture 4 | ['c', 'a', 'b'] | ['c', 'a', 'b'] | Passed |
| contract fixture 5 | ['b', 'a'] | ['b', 'a'] | Passed |
| contract fixture 6 | [] | [] | Passed |
| contract fixture 7 | ['', 'a'] | ['', 'a'] | Passed |
| contract fixture 8 | ['only'] | ['only'] | Passed |
SHA-256 / 0f78db5edc6d779198f896449a8df5ac174ca9cb48306b3a87e55ff1357d46d4
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(data):
natural,edges,excluded,start = data
items = list(dict.fromkeys(x for x in natural if x not in excluded))
if not items: return []
links = {}
for source,target in edges:
if source not in items or target is None or source == target: continue
links.setdefault(source,target)
current = start if start in items else items[0]
seen = set()
result = []
while current is not None:
result.append(current)
seen.add(current)
nxt = links.get(current)
current = nxt if nxt is not None and nxt not in seen else next((x for x in items if x not in seen),None)
return result
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([['a','b','c',str(N)],[['a','c'],['c','a']],[],'a'],), ['a','c','b',str(N)])
check('contract fixture 2', solve([['a','b','c'],[['a','c'],['a','b']],[],'a'],), ['a','c','b'])
check('contract fixture 3', solve([['a','b','c'],[['a','b'],['a','missing']],['b'],'a'],), ['a','c'])
check('contract fixture 4', solve([['a','b','c'],[],[],'c'],), ['c','a','b'])
check('contract fixture 5', solve([['b','a','b'],[['b','b']],[],'missing'],), ['b','a'])
check('contract fixture 6', solve([['a'],[['a','missing']],['a'],'a'],), [])
check('contract fixture 7', solve([['','a'],[['','a']],[],''],), ['','a'])
check('contract fixture 8', solve([['only'],[],[],'only'],), ['only'])
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 | ['a', 'c', 'b', '1'] | ['a', 'c', 'b', '1'] | Passed |
| contract fixture 2 | ['a', 'c', 'b'] | ['a', 'c', 'b'] | Passed |
| contract fixture 3 | ['a', 'b', 'c'] | ['a', 'c'] | Failed |
| contract fixture 4 | ['c', 'a', 'b'] | ['c', 'a', 'b'] | Passed |
| contract fixture 5 | ['b', 'a'] | ['b', 'a'] | Passed |
| contract fixture 6 | [] | [] | Passed |
| contract fixture 7 | ['', 'a'] | ['', 'a'] | Passed |
| contract fixture 8 | ['only'] | ['only'] | Passed |
SHA-256 / dadada24ed783cecc69a9f65b3958fa3eae3938413026e3fcc04aa2b6b73f2b8
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(data):
natural,edges,excluded,start = data
items = list(dict.fromkeys(x for x in natural if x not in excluded))
if not items: return []
links = {}
for source,target in edges:
if source not in items or target not in items or source == target: continue
links.setdefault(source,target)
current = start if start in items else items[0]
seen = set()
result = []
while current is not None:
result.append(current)
seen.add(current)
nxt = links.get(current)
current = nxt if nxt is not None and nxt not in seen else next((x for x in items if x not in seen),None)
return result
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([['a','b','c',str(N)],[['a','c'],['c','a']],[],'a'],), ['a','c','b',str(N)])
check('contract fixture 2', solve([['a','b','c'],[['a','c'],['a','b']],[],'a'],), ['a','c','b'])
check('contract fixture 3', solve([['a','b','c'],[['a','b'],['a','missing']],['b'],'a'],), ['a','c'])
check('contract fixture 4', solve([['a','b','c'],[],[],'c'],), ['c','a','b'])
check('contract fixture 5', solve([['b','a','b'],[['b','b']],[],'missing'],), ['b','a'])
check('contract fixture 6', solve([['a'],[['a','missing']],['a'],'a'],), [])
check('contract fixture 7', solve([['','a'],[['','a']],[],''],), ['','a'])
check('contract fixture 8', solve([['only'],[],[],'only'],), ['only'])
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 | ['a', 'c', 'b', '1'] | ['a', 'c', 'b', '1'] | Passed |
| contract fixture 2 | ['a', 'c', 'b'] | ['a', 'c', 'b'] | Passed |
| contract fixture 3 | ['a', 'c'] | ['a', 'c'] | Passed |
| contract fixture 4 | ['c', 'a', 'b'] | ['c', 'a', 'b'] | Passed |
| contract fixture 5 | ['b', 'a'] | ['b', 'a'] | Passed |
| contract fixture 6 | [] | [] | Passed |
| contract fixture 7 | ['', 'a'] | ['', 'a'] | Passed |
| contract fixture 8 | ['only'] | ['only'] | Passed |
SHA-256 / 6d5993fe7933f3c0c4a2c3f2685fa0f8720c7261ba749e503681cea5f1296e08
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 2026-09-29T14:45:43.396651+00:00.
Case digest / 88e0373a4515304f23b4077b1d293035079a0d13e5da13d1d176b34c67bc4f5b