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FA-31411 / Keyboard interactions / Open access

Keyboard default edit cancellation pipeline: Forward delete extends an existing selection or consumes two characters · case 01

The event trace violates the delete selection rule and produces incorrect keyboard state or command output.

Verified by executionVariant 1 · 13 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Forward delete extends an existing selection or consumes two characters.

THE FAILURE

Forward delete extends an existing selection or consumes two characters.

Unsuccessful approach: The partial repair changes this transition to elif key=='Delete' and lo==hi: hi=min(len(text),hi+2), which still violates the model contract on the explicit regression traces.

Case contract

Case [text,lo,hi,key,prevent_down,prevent_before,cancelable,readonly]. Selection is a valid half-open code-point interval. Printable single characters replace selection, Backspace deletes previous point and Delete deletes next point for collapsed selections. Other keys do not edit. A cancelable prevented keydown stops editing; readonly suppresses beforeinput. A changed candidate fires beforeinput, cancellation suppresses mutation; successful edit fires input. Always log keydown and keyup. Return text, selection endpoints and event log. Inputs are finite ordered event traces; return the stated deterministic state. Batch entries are independent. N varies the number of independent input transactions.

Why this case matters

Controlled keyboard event processing model for debugging application event logic.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(cases):
    def run(c):
        text,lo,hi,key,prevent_down,prevent_before,cancelable,readonly=c
        log=['keydown']; original=[text,lo,hi]
        if prevent_down and cancelable:
            return original+[log+['keyup']]
        if readonly or not (len(key)==1 or key in ('Backspace','Delete')):
            return original+[log+['keyup']]
        insert=key if len(key)==1 else ''
        if key=='Backspace' and lo==hi: lo=max(0,lo-1)
        elif key=='Delete': hi=min(len(text),hi+1)
        changed=text[:lo]+insert+text[hi:]
        if changed==text:
            return original+[log+['keyup']]
        log.append('beforeinput')
        if prevent_before:
            return original+[log+['keyup']]
        text=changed
        hi=lo+len(insert); lo=hi
        log.append('input')
        return [text,lo,hi,log+['keyup']]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('key-default-edit scenario 0', solve([['abc', 1, 1, 'X', False, False, True, False]] * N), [['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 1', solve([['abc', 1, 2, 'XY', False, False, True, False]] * N), [['abc', 1, 2, ['keydown', 'keyup']]] * N)
check('key-default-edit scenario 2', solve([['abcd', 1, 3, 'Z', False, False, True, False]] * N), [['aZd', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 3', solve([['abcd', 1, 3, 'Backspace', False, False, True, False]] * N), [['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 4', solve([['abcd', 1, 3, 'Delete', False, False, True, False]] * N), [['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 5', solve([['abcd', 2, 2, 'Backspace', False, False, True, False]] * N), [['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 6', solve([['abcd', 1, 1, 'Delete', False, False, True, False]] * N), [['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 7', solve([['abc', 0, 0, 'Backspace', False, False, True, False]] * N), [['abc', 0, 0, ['keydown', 'keyup']]] * N)
check('key-default-edit scenario 8', solve([['abc', 0, 3, 'Delete', False, False, True, False]] * N), [['', 0, 0, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 9', solve([['abc', 1, 1, 'X', True, False, False, False]] * N), [['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 10', solve([['abc', 1, 1, 'X', True, False, True, False]] * N), [['abc', 1, 1, ['keydown', 'keyup']]] * N)
check('key-default-edit scenario 11', solve([['abc', 1, 1, 'X', False, True, False, False]] * N), [['abc', 1, 1, ['keydown', 'beforeinput', 'keyup']]] * N)
check('key-default-edit scenario 12', solve([['abc', 1, 1, 'X', False, False, True, True]] * N), [['abc', 1, 1, ['keydown', 'keyup']]] * 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 fixtureActualExpectedOutcome
key-default-edit scenario 0[['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]][['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 1[['abc', 1, 2, ['keydown', 'keyup']]][['abc', 1, 2, ['keydown', 'keyup']]]Passed
key-default-edit scenario 2[['aZd', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]][['aZd', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 3[['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 4[['a', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Failed
key-default-edit scenario 5[['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 6[['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 7[['abc', 0, 0, ['keydown', 'keyup']]][['abc', 0, 0, ['keydown', 'keyup']]]Passed
key-default-edit scenario 8[['', 0, 0, ['keydown', 'beforeinput', 'input', 'keyup']]][['', 0, 0, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 9[['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]][['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 10[['abc', 1, 1, ['keydown', 'keyup']]][['abc', 1, 1, ['keydown', 'keyup']]]Passed
key-default-edit scenario 11[['abc', 1, 1, ['keydown', 'beforeinput', 'keyup']]][['abc', 1, 1, ['keydown', 'beforeinput', 'keyup']]]Passed
key-default-edit scenario 12[['abc', 1, 1, ['keydown', 'keyup']]][['abc', 1, 1, ['keydown', 'keyup']]]Passed

SHA-256 / 8eb924609dada78456f2ba98a3428380d5337d6a3e68c028af6dad34eada0e05

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(cases):
    def run(c):
        text,lo,hi,key,prevent_down,prevent_before,cancelable,readonly=c
        log=['keydown']; original=[text,lo,hi]
        if prevent_down and cancelable:
            return original+[log+['keyup']]
        if readonly or not (len(key)==1 or key in ('Backspace','Delete')):
            return original+[log+['keyup']]
        insert=key if len(key)==1 else ''
        if key=='Backspace' and lo==hi: lo=max(0,lo-1)
        elif key=='Delete' and lo==hi: hi=min(len(text),hi+2)
        changed=text[:lo]+insert+text[hi:]
        if changed==text:
            return original+[log+['keyup']]
        log.append('beforeinput')
        if prevent_before:
            return original+[log+['keyup']]
        text=changed
        hi=lo+len(insert); lo=hi
        log.append('input')
        return [text,lo,hi,log+['keyup']]
    return [run(c) for c in cases]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('key-default-edit scenario 0', solve([['abc', 1, 1, 'X', False, False, True, False]] * N), [['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 1', solve([['abc', 1, 2, 'XY', False, False, True, False]] * N), [['abc', 1, 2, ['keydown', 'keyup']]] * N)
check('key-default-edit scenario 2', solve([['abcd', 1, 3, 'Z', False, False, True, False]] * N), [['aZd', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 3', solve([['abcd', 1, 3, 'Backspace', False, False, True, False]] * N), [['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 4', solve([['abcd', 1, 3, 'Delete', False, False, True, False]] * N), [['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 5', solve([['abcd', 2, 2, 'Backspace', False, False, True, False]] * N), [['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 6', solve([['abcd', 1, 1, 'Delete', False, False, True, False]] * N), [['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 7', solve([['abc', 0, 0, 'Backspace', False, False, True, False]] * N), [['abc', 0, 0, ['keydown', 'keyup']]] * N)
check('key-default-edit scenario 8', solve([['abc', 0, 3, 'Delete', False, False, True, False]] * N), [['', 0, 0, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 9', solve([['abc', 1, 1, 'X', True, False, False, False]] * N), [['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]] * N)
check('key-default-edit scenario 10', solve([['abc', 1, 1, 'X', True, False, True, False]] * N), [['abc', 1, 1, ['keydown', 'keyup']]] * N)
check('key-default-edit scenario 11', solve([['abc', 1, 1, 'X', False, True, False, False]] * N), [['abc', 1, 1, ['keydown', 'beforeinput', 'keyup']]] * N)
check('key-default-edit scenario 12', solve([['abc', 1, 1, 'X', False, False, True, True]] * N), [['abc', 1, 1, ['keydown', 'keyup']]] * 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 fixtureActualExpectedOutcome
key-default-edit scenario 0[['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]][['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 1[['abc', 1, 2, ['keydown', 'keyup']]][['abc', 1, 2, ['keydown', 'keyup']]]Passed
key-default-edit scenario 2[['aZd', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]][['aZd', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 3[['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 4[['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 5[['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 6[['ad', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]][['acd', 1, 1, ['keydown', 'beforeinput', 'input', 'keyup']]]Failed
key-default-edit scenario 7[['abc', 0, 0, ['keydown', 'keyup']]][['abc', 0, 0, ['keydown', 'keyup']]]Passed
key-default-edit scenario 8[['', 0, 0, ['keydown', 'beforeinput', 'input', 'keyup']]][['', 0, 0, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 9[['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]][['aXbc', 2, 2, ['keydown', 'beforeinput', 'input', 'keyup']]]Passed
key-default-edit scenario 10[['abc', 1, 1, ['keydown', 'keyup']]][['abc', 1, 1, ['keydown', 'keyup']]]Passed
key-default-edit scenario 11[['abc', 1, 1, ['keydown', 'beforeinput', 'keyup']]][['abc', 1, 1, ['keydown', 'beforeinput', 'keyup']]]Passed
key-default-edit scenario 12[['abc', 1, 1, ['keydown', 'keyup']]][['abc', 1, 1, ['keydown', 'keyup']]]Passed

SHA-256 / 605b8cc65e37c23fa7a13e38b90e2bb8a791d4793b798e467695ee7e17633b24

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 13 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.

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Verification & scope

Offline stipulated event model, not a browser implementation or web standard conformance claim. 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 2026-09-29T14:42:02.025624+00:00.

Case digest / 9e280131065ec8031f8489c19520753bd6c3642f8756b42a1bc47734f45f950c