FA-53801 / Accessibility interaction semantics / Open access
New attribute runs start with an empty interval · case 01
New attribute runs start with an empty interval.
ROOT CAUSE
The initial end decision in the text attribute runs adapter violates its declared contract.
THE FAILURE
The initial end decision in the text attribute runs adapter violates its declared contract.
Unsuccessful approach: The local repair substitutes result.append([pos,pos+2,attrs]) but still mishandles the regression fixtures.
Case contract
Input [length,default_attributes,spans] where spans are [start,end,attributes,priority]. Clamp endpoints to [0,length], discard empty/reversed spans. At each character position merge active spans over defaults by increasing priority, preserving input tie order; None attribute removes that attribute. Build maximal equal adjacent runs [start,end,attributes]. Zero length returns empty. Offsets are codepoints. Dictionary values are strings or 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):
length,defaults,spans = data
points = []
for pos in range(length):
attrs = dict(defaults)
active = [(p,i,a) for i,(s,e,a,p) in enumerate(spans) if max(0,s) <= pos < min(length,e)]
for priority,idx,updates in sorted(active,key=lambda x:(x[0],x[1])):
for key,value in updates.items():
if value is None: attrs.pop(key,None)
else: attrs[key] = value
points.append(attrs)
result = []
for pos,attrs in enumerate(points):
if result and result[-1][2] == attrs: result[-1][1] = pos+1
else: result.append([pos,pos,attrs])
return result
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([N+2,{'lang':'en'},[[0,N,{'weight':'bold'},1],[1,N+1,{'lang':'fr'},2]]],), [[0,1,{'lang':'en','weight':'bold'}]]+([[1,N,{'lang':'fr','weight':'bold'}]] if N>1 else [])+[[N,N+1,{'lang':'fr'}],[N+1,N+2,{'lang':'en'}]])
check('contract fixture 2', solve([3,{'lang':'en','color':'red'},[[0,3,{'lang':None},1],[1,2,{'color':'blue'},2]]],), [[0,1,{'color':'red'}],[1,2,{'color':'blue'}],[2,3,{'color':'red'}]])
check('contract fixture 3', solve([3,{},[[0,3,{'x':'high'},5],[0,3,{'x':'low'},1]]],), [[0,3,{'x':'high'}]])
check('contract fixture 4', solve([3,{},[[0,3,{'x':'first'},1],[0,3,{'x':'last'},1]]],), [[0,3,{'x':'last'}]])
check('contract fixture 5', solve([3,{},[[-3,2,{'x':'a'},0],[2,8,{'x':'a'},0],[2,1,{'x':'bad'},9]]],), [[0,3,{'x':'a'}]])
check('contract fixture 6', solve([0,{'lang':'en'},[]],), [])
check('contract fixture 7', solve([2,{'lang':'en'},[[0,1,{},0]]],), [[0,2,{'lang':'en'}]])
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 | [[0, 0, {'lang': 'en', 'weight': 'bold'}], [1, 1, {'lang': 'fr'}], [2, 2, {'lang': 'en'}]] | [[0, 1, {'lang': 'en', 'weight': 'bold'}], [1, 2, {'lang': 'fr'}], [2, 3, {'lang': 'en'}]] | Failed |
| contract fixture 2 | [[0, 0, {'color': 'red'}], [1, 1, {'color': 'blue'}], [2, 2, {'color': 'red'}]] | [[0, 1, {'color': 'red'}], [1, 2, {'color': 'blue'}], [2, 3, {'color': 'red'}]] | Failed |
| contract fixture 3 | [[0, 3, {'x': 'high'}]] | [[0, 3, {'x': 'high'}]] | Passed |
| contract fixture 4 | [[0, 3, {'x': 'last'}]] | [[0, 3, {'x': 'last'}]] | Passed |
| contract fixture 5 | [[0, 3, {'x': 'a'}]] | [[0, 3, {'x': 'a'}]] | Passed |
| contract fixture 6 | [] | [] | Passed |
| contract fixture 7 | [[0, 2, {'lang': 'en'}]] | [[0, 2, {'lang': 'en'}]] | Passed |
SHA-256 / a36afa58ff3b3817fcd0ad220c6604dd579ac51f595bf3cd0036132e1841a11f
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(data):
length,defaults,spans = data
points = []
for pos in range(length):
attrs = dict(defaults)
active = [(p,i,a) for i,(s,e,a,p) in enumerate(spans) if max(0,s) <= pos < min(length,e)]
for priority,idx,updates in sorted(active,key=lambda x:(x[0],x[1])):
for key,value in updates.items():
if value is None: attrs.pop(key,None)
else: attrs[key] = value
points.append(attrs)
result = []
for pos,attrs in enumerate(points):
if result and result[-1][2] == attrs: result[-1][1] = pos+1
else: result.append([pos,pos+2,attrs])
return result
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('contract fixture 1', solve([N+2,{'lang':'en'},[[0,N,{'weight':'bold'},1],[1,N+1,{'lang':'fr'},2]]],), [[0,1,{'lang':'en','weight':'bold'}]]+([[1,N,{'lang':'fr','weight':'bold'}]] if N>1 else [])+[[N,N+1,{'lang':'fr'}],[N+1,N+2,{'lang':'en'}]])
check('contract fixture 2', solve([3,{'lang':'en','color':'red'},[[0,3,{'lang':None},1],[1,2,{'color':'blue'},2]]],), [[0,1,{'color':'red'}],[1,2,{'color':'blue'}],[2,3,{'color':'red'}]])
check('contract fixture 3', solve([3,{},[[0,3,{'x':'high'},5],[0,3,{'x':'low'},1]]],), [[0,3,{'x':'high'}]])
check('contract fixture 4', solve([3,{},[[0,3,{'x':'first'},1],[0,3,{'x':'last'},1]]],), [[0,3,{'x':'last'}]])
check('contract fixture 5', solve([3,{},[[-3,2,{'x':'a'},0],[2,8,{'x':'a'},0],[2,1,{'x':'bad'},9]]],), [[0,3,{'x':'a'}]])
check('contract fixture 6', solve([0,{'lang':'en'},[]],), [])
check('contract fixture 7', solve([2,{'lang':'en'},[[0,1,{},0]]],), [[0,2,{'lang':'en'}]])
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 | [[0, 2, {'lang': 'en', 'weight': 'bold'}], [1, 3, {'lang': 'fr'}], [2, 4, {'lang': 'en'}]] | [[0, 1, {'lang': 'en', 'weight': 'bold'}], [1, 2, {'lang': 'fr'}], [2, 3, {'lang': 'en'}]] | Failed |
| contract fixture 2 | [[0, 2, {'color': 'red'}], [1, 3, {'color': 'blue'}], [2, 4, {'color': 'red'}]] | [[0, 1, {'color': 'red'}], [1, 2, {'color': 'blue'}], [2, 3, {'color': 'red'}]] | Failed |
| contract fixture 3 | [[0, 3, {'x': 'high'}]] | [[0, 3, {'x': 'high'}]] | Passed |
| contract fixture 4 | [[0, 3, {'x': 'last'}]] | [[0, 3, {'x': 'last'}]] | Passed |
| contract fixture 5 | [[0, 3, {'x': 'a'}]] | [[0, 3, {'x': 'a'}]] | Passed |
| contract fixture 6 | [] | [] | Passed |
| contract fixture 7 | [[0, 2, {'lang': 'en'}]] | [[0, 2, {'lang': 'en'}]] | Passed |
SHA-256 / 92e749f3d29e44b3382d2d747065af5807d1e0c710dfc993517d839c3cdfb6e8
HELD IN THE MEMBER ARCHIVE
The verified repair and its recorded checks are member-only.
This mechanism has 7 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.
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 2026-09-29T14:45:42.450188+00:00.
Case digest / 0ac12d0c9eca56eb79eedc3186536125c1c2c81895da02785db30d6963e88426