FA-53946 / Accessibility interaction semantics / Open access

A reading-flow cycle truncates unrelated remaining objects · case 01

A reading-flow cycle truncates unrelated remaining objects.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The cycle fallback decision in the reading flow adapter violates its declared contract.

THE FAILURE

The cycle fallback decision in the reading flow adapter violates its declared contract.

Unsuccessful approach: The local repair substitutes current = None if nxt in seen else (nxt if nxt is not None else next((x for x in items if x not in seen),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 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 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']`	`['a', 'c', 'b', '1']`	Failed
contract fixture 2	`['a', 'c']`	`['a', 'c', 'b']`	Failed
contract fixture 3	`['a']`	`['a', 'c']`	Failed
contract fixture 4	`['c']`	`['c', 'a', 'b']`	Failed
contract fixture 5	`['b']`	`['b', 'a']`	Failed
contract fixture 6	`[]`	`[]`	Passed
contract fixture 7	`['', 'a']`	`['', 'a']`	Passed
contract fixture 8	`['only']`	`['only']`	Passed

SHA-256 / 42cf6ec98e3fc8d91561b88c265f60c2e3db81f6e49405f3f90d71cac7d3f7a4

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 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 = None if nxt in seen else (nxt if nxt is not None 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']`	`['a', 'c', 'b', '1']`	Failed
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 / c20850d31bb6d54b112719298da067fe7c240dcd2abb6da1b8493393e716c107

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 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.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

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 2026-09-29T14:45:43.846653+00:00.

Case digest / 9da7cf04fd67cb19e90f03d6ba40197ff3fa725f1615bbffc3f2974f3aca572d