FA-54216 / Accessibility interaction semantics / Open access
Empty braille cells disappear instead of occupying a display slot · case 01
Empty braille cells disappear instead of occupying a display slot.
ROOT CAUSE
The empty cells decision in the braille routing adapter violates its declared contract.
VERIFIED REPAIR
Apply the exact contract at the empty cells decision: (c if c else ' ')
Unsuccessful approach: The local repair substitutes (c if c else '') but still mishandles the regression fixtures.
Case contract
Input [cells,offset,width,route] where cells [source_start,source_end,content,editable]. Clip display window by nonnegative offset and width. Each cell has one display position regardless of content length. Routing uses a zero-based position inside displayed cells; return None if outside window or cell not editable, otherwise [source_start,source_end]. Display contents replace empty cell content with a space; protected content (exact token SECRET) displays a bullet. Return [display,source_ranges,route_result,has_previous,has_next]. Source ranges preserve zero-width insertion cells.
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):
cells,offset,width,route = data
offset,width = max(0,offset),max(0,width)
window = cells[offset:offset+width]
contents = [('•' if c == 'SECRET' else c) for s,e,c,editable in window]
ranges = [[s,e] for s,e,c,editable in window]
routed = None
if 0 <= route < len(window):
s,e,c,editable = window[route]
if editable: routed = [s,e]
return [contents,ranges,routed,offset>0,offset+len(window)<len(cells)]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([[[0,N,'ab',True],[N,N+2,'SECRET',False],[N+2,N+2,'',True]],1,2,1],), [['•',' '],[[N,N+2],[N+2,N+2]],[N+2,N+2],True,False])
check('contract fixture 2', solve([[[0,2,'ab',True],[2,3,'c',True],[3,4,'d',True]],0,2,0],), [['ab','c'],[[0,2],[2,3]],[0,2],False,True])
check('contract fixture 3', solve([[[0,1,'x',False]],0,1,0],), [['x'],[[0,1]],None,False,False])
check('contract fixture 4', solve([[[0,1,'x',True]],0,1,-1],), [['x'],[[0,1]],None,False,False])
check('contract fixture 5', solve([[[0,1,'x',True]],0,1,1],), [['x'],[[0,1]],None,False,False])
check('contract fixture 6', solve([[[0,1,'x',True]],-2,0,0],), [[],[],None,False,True])
check('contract fixture 7', solve([[[0,1,'a',True],[1,2,'b',True]],-1,1,0],), [['a'],[[0,1]],[0,1],False,True])
check('contract fixture 8', solve([[],0,4,0],), [[],[],None,False,False])
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 | [['•', ''], [[1, 3], [3, 3]], [3, 3], True, False] | [['•', ' '], [[1, 3], [3, 3]], [3, 3], True, False] | Failed |
| contract fixture 2 | [['ab', 'c'], [[0, 2], [2, 3]], [0, 2], False, True] | [['ab', 'c'], [[0, 2], [2, 3]], [0, 2], False, True] | Passed |
| contract fixture 3 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 4 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 5 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 6 | [[], [], None, False, True] | [[], [], None, False, True] | Passed |
| contract fixture 7 | [['a'], [[0, 1]], [0, 1], False, True] | [['a'], [[0, 1]], [0, 1], False, True] | Passed |
| contract fixture 8 | [[], [], None, False, False] | [[], [], None, False, False] | Passed |
SHA-256 / e8266cc4188932218993dda1108852acf3248f5bc40c61723d8e5ee23b33d3f2
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(data):
cells,offset,width,route = data
offset,width = max(0,offset),max(0,width)
window = cells[offset:offset+width]
contents = [('•' if c == 'SECRET' else (c if c else '')) for s,e,c,editable in window]
ranges = [[s,e] for s,e,c,editable in window]
routed = None
if 0 <= route < len(window):
s,e,c,editable = window[route]
if editable: routed = [s,e]
return [contents,ranges,routed,offset>0,offset+len(window)<len(cells)]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([[[0,N,'ab',True],[N,N+2,'SECRET',False],[N+2,N+2,'',True]],1,2,1],), [['•',' '],[[N,N+2],[N+2,N+2]],[N+2,N+2],True,False])
check('contract fixture 2', solve([[[0,2,'ab',True],[2,3,'c',True],[3,4,'d',True]],0,2,0],), [['ab','c'],[[0,2],[2,3]],[0,2],False,True])
check('contract fixture 3', solve([[[0,1,'x',False]],0,1,0],), [['x'],[[0,1]],None,False,False])
check('contract fixture 4', solve([[[0,1,'x',True]],0,1,-1],), [['x'],[[0,1]],None,False,False])
check('contract fixture 5', solve([[[0,1,'x',True]],0,1,1],), [['x'],[[0,1]],None,False,False])
check('contract fixture 6', solve([[[0,1,'x',True]],-2,0,0],), [[],[],None,False,True])
check('contract fixture 7', solve([[[0,1,'a',True],[1,2,'b',True]],-1,1,0],), [['a'],[[0,1]],[0,1],False,True])
check('contract fixture 8', solve([[],0,4,0],), [[],[],None,False,False])
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 | [['•', ''], [[1, 3], [3, 3]], [3, 3], True, False] | [['•', ' '], [[1, 3], [3, 3]], [3, 3], True, False] | Failed |
| contract fixture 2 | [['ab', 'c'], [[0, 2], [2, 3]], [0, 2], False, True] | [['ab', 'c'], [[0, 2], [2, 3]], [0, 2], False, True] | Passed |
| contract fixture 3 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 4 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 5 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 6 | [[], [], None, False, True] | [[], [], None, False, True] | Passed |
| contract fixture 7 | [['a'], [[0, 1]], [0, 1], False, True] | [['a'], [[0, 1]], [0, 1], False, True] | Passed |
| contract fixture 8 | [[], [], None, False, False] | [[], [], None, False, False] | Passed |
SHA-256 / d8fd59fa729e26a123ea2352b186249f824e6f8f0768c874c0dde9f387a17e60
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(data):
cells,offset,width,route = data
offset,width = max(0,offset),max(0,width)
window = cells[offset:offset+width]
contents = [('•' if c == 'SECRET' else (c if c else ' ')) for s,e,c,editable in window]
ranges = [[s,e] for s,e,c,editable in window]
routed = None
if 0 <= route < len(window):
s,e,c,editable = window[route]
if editable: routed = [s,e]
return [contents,ranges,routed,offset>0,offset+len(window)<len(cells)]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([[[0,N,'ab',True],[N,N+2,'SECRET',False],[N+2,N+2,'',True]],1,2,1],), [['•',' '],[[N,N+2],[N+2,N+2]],[N+2,N+2],True,False])
check('contract fixture 2', solve([[[0,2,'ab',True],[2,3,'c',True],[3,4,'d',True]],0,2,0],), [['ab','c'],[[0,2],[2,3]],[0,2],False,True])
check('contract fixture 3', solve([[[0,1,'x',False]],0,1,0],), [['x'],[[0,1]],None,False,False])
check('contract fixture 4', solve([[[0,1,'x',True]],0,1,-1],), [['x'],[[0,1]],None,False,False])
check('contract fixture 5', solve([[[0,1,'x',True]],0,1,1],), [['x'],[[0,1]],None,False,False])
check('contract fixture 6', solve([[[0,1,'x',True]],-2,0,0],), [[],[],None,False,True])
check('contract fixture 7', solve([[[0,1,'a',True],[1,2,'b',True]],-1,1,0],), [['a'],[[0,1]],[0,1],False,True])
check('contract fixture 8', solve([[],0,4,0],), [[],[],None,False,False])
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 | [['•', ' '], [[1, 3], [3, 3]], [3, 3], True, False] | [['•', ' '], [[1, 3], [3, 3]], [3, 3], True, False] | Passed |
| contract fixture 2 | [['ab', 'c'], [[0, 2], [2, 3]], [0, 2], False, True] | [['ab', 'c'], [[0, 2], [2, 3]], [0, 2], False, True] | Passed |
| contract fixture 3 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 4 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 5 | [['x'], [[0, 1]], None, False, False] | [['x'], [[0, 1]], None, False, False] | Passed |
| contract fixture 6 | [[], [], None, False, True] | [[], [], None, False, True] | Passed |
| contract fixture 7 | [['a'], [[0, 1]], [0, 1], False, True] | [['a'], [[0, 1]], [0, 1], False, True] | Passed |
| contract fixture 8 | [[], [], None, False, False] | [[], [], None, False, False] | Passed |
SHA-256 / 9366225523c4f8d0d94e6737016ceee05746c3c7b4829d345dbeaa6ea661fe4d
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 2026-09-29T14:45:46.293934+00:00.
Case digest / ff281967b63830c599bd39c0dcd6e95ff34984b827108fbdf169b9f901105efb