FA-22806 / Autocomplete interactions / Open access

Undoable autocomplete acceptance: redo appends completion text onto the old prefix · case 01

The redo-text completion transition produces an incorrect observable state.

Verified by executionVariant 1 · 22 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

At completion-undo/redo-text, the implementation evaluates `d['before']['text']+d['after']['text']` instead of preserving the specified completion transition.

THE FAILURE

At completion-undo/redo-text, the implementation evaluates `d['before']['text']+d['after']['text']` instead of preserving the specified completion transition.

Unsuccessful approach: The attempted repair uses `d['before']['text']`, which still violates a normal or boundary completion fixture.

Case contract

A completion acceptance is one undo transaction containing draft, committed identity and caret. Undo restores the pre-accept snapshot; redo restores the accepted snapshot. A subsequent edit discards redo, transient hover never enters the stack, and history snapshots own their data.

Why this case matters

Autocomplete couples draft text, suggestion identity and asynchronous presentation; this bounded lifecycle model isolates one observable interaction defect.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(event, d):
    if event == 'undo-text': return d['before']['text']
    if event == 'undo-value': return d['before']['value']
    if event == 'undo-caret': return d['before']['caret']
    if event == 'redo-text': return d['before']['text']+d['after']['text']
    if event == 'redo-value': return d['after']['value']
    if event == 'redo-caret': return d['after']['caret']
    if event == 'edit': return []
    if event == 'transaction': return d['undo']+[d['before']]
    if event == 'hover': return d['undo']
    if event == 'redo-divergence': return d['draft']==d['before']['text']
    return {'unchanged': True}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
normal = {'before':{'text':'pea','value':None,'caret':3},'after':{'text':'pear','value':'p1','caret':4},'undo':['u1'],'redo':['r1'],'hover':'p2','draft':'pear!','epoch':N}
boundary = {'before':{'text':'','value':'','caret':0},'after':{'text':'x','value':'x1','caret':1},'undo':[],'redo':[],'hover':None,'draft':'','epoch':N}
check('normal undo-text', solve('undo-text', normal), 'pea')
check('boundary undo-text', solve('undo-text', boundary), '')
check('normal undo-value', solve('undo-value', normal), None)
check('boundary undo-value', solve('undo-value', boundary), '')
check('normal undo-caret', solve('undo-caret', normal), 3)
check('boundary undo-caret', solve('undo-caret', boundary), 0)
check('normal redo-text', solve('redo-text', normal), 'pear')
check('boundary redo-text', solve('redo-text', boundary), 'x')
check('normal redo-value', solve('redo-value', normal), 'p1')
check('boundary redo-value', solve('redo-value', boundary), 'x1')
check('normal redo-caret', solve('redo-caret', normal), 4)
check('boundary redo-caret', solve('redo-caret', boundary), 1)
check('normal edit', solve('edit', normal), [])
check('boundary edit', solve('edit', boundary), [])
check('normal transaction', solve('transaction', normal), ['u1',{'text':'pea','value':None,'caret':3}])
check('boundary transaction', solve('transaction', boundary), [{'text':'','value':'','caret':0}])
check('normal hover', solve('hover', normal), ['u1'])
check('boundary hover', solve('hover', boundary), [])
check('normal redo-divergence', solve('redo-divergence', normal), False)
check('boundary redo-divergence', solve('redo-divergence', boundary), True)
variant = dict(normal, **{'after':{'text':'p'*N,'value':'p','caret':N}})
check('variant query or selection payload', solve('redo-text', variant), 'p'*N)
check('unknown completion event', solve('unrecognized', normal), {'unchanged': True})
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
normal undo-text	`pea`	`pea`	Passed
boundary undo-text			Passed
normal undo-value	`None`	`None`	Passed
boundary undo-value			Passed
normal undo-caret	`3`	`3`	Passed
boundary undo-caret	`0`	`0`	Passed
normal redo-text	`peapear`	`pear`	Failed
boundary redo-text	`x`	`x`	Passed
normal redo-value	`p1`	`p1`	Passed
boundary redo-value	`x1`	`x1`	Passed
normal redo-caret	`4`	`4`	Passed
boundary redo-caret	`1`	`1`	Passed
normal edit	`[]`	`[]`	Passed
boundary edit	`[]`	`[]`	Passed
normal transaction	`['u1', {'caret': 3, 'text': 'pea', 'value': None}]`	`['u1', {'caret': 3, 'text': 'pea', 'value': None}]`	Passed
boundary transaction	`[{'caret': 0, 'text': '', 'value': ''}]`	`[{'caret': 0, 'text': '', 'value': ''}]`	Passed
normal hover	`['u1']`	`['u1']`	Passed
boundary hover	`[]`	`[]`	Passed
normal redo-divergence	`False`	`False`	Passed
boundary redo-divergence	`True`	`True`	Passed
variant query or selection payload	`peap`	`p`	Failed
unknown completion event	`{'unchanged': True}`	`{'unchanged': True}`	Passed

SHA-256 / e09aaa01318a5fea3e0fb84b119e7e20beb8043ed385ee57e4c5302919e37050

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(event, d):
    if event == 'undo-text': return d['before']['text']
    if event == 'undo-value': return d['before']['value']
    if event == 'undo-caret': return d['before']['caret']
    if event == 'redo-text': return d['before']['text']
    if event == 'redo-value': return d['after']['value']
    if event == 'redo-caret': return d['after']['caret']
    if event == 'edit': return []
    if event == 'transaction': return d['undo']+[d['before']]
    if event == 'hover': return d['undo']
    if event == 'redo-divergence': return d['draft']==d['before']['text']
    return {'unchanged': True}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
normal = {'before':{'text':'pea','value':None,'caret':3},'after':{'text':'pear','value':'p1','caret':4},'undo':['u1'],'redo':['r1'],'hover':'p2','draft':'pear!','epoch':N}
boundary = {'before':{'text':'','value':'','caret':0},'after':{'text':'x','value':'x1','caret':1},'undo':[],'redo':[],'hover':None,'draft':'','epoch':N}
check('normal undo-text', solve('undo-text', normal), 'pea')
check('boundary undo-text', solve('undo-text', boundary), '')
check('normal undo-value', solve('undo-value', normal), None)
check('boundary undo-value', solve('undo-value', boundary), '')
check('normal undo-caret', solve('undo-caret', normal), 3)
check('boundary undo-caret', solve('undo-caret', boundary), 0)
check('normal redo-text', solve('redo-text', normal), 'pear')
check('boundary redo-text', solve('redo-text', boundary), 'x')
check('normal redo-value', solve('redo-value', normal), 'p1')
check('boundary redo-value', solve('redo-value', boundary), 'x1')
check('normal redo-caret', solve('redo-caret', normal), 4)
check('boundary redo-caret', solve('redo-caret', boundary), 1)
check('normal edit', solve('edit', normal), [])
check('boundary edit', solve('edit', boundary), [])
check('normal transaction', solve('transaction', normal), ['u1',{'text':'pea','value':None,'caret':3}])
check('boundary transaction', solve('transaction', boundary), [{'text':'','value':'','caret':0}])
check('normal hover', solve('hover', normal), ['u1'])
check('boundary hover', solve('hover', boundary), [])
check('normal redo-divergence', solve('redo-divergence', normal), False)
check('boundary redo-divergence', solve('redo-divergence', boundary), True)
variant = dict(normal, **{'after':{'text':'p'*N,'value':'p','caret':N}})
check('variant query or selection payload', solve('redo-text', variant), 'p'*N)
check('unknown completion event', solve('unrecognized', normal), {'unchanged': True})
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
normal undo-text	`pea`	`pea`	Passed
boundary undo-text			Passed
normal undo-value	`None`	`None`	Passed
boundary undo-value			Passed
normal undo-caret	`3`	`3`	Passed
boundary undo-caret	`0`	`0`	Passed
normal redo-text	`pea`	`pear`	Failed
boundary redo-text		`x`	Failed
normal redo-value	`p1`	`p1`	Passed
boundary redo-value	`x1`	`x1`	Passed
normal redo-caret	`4`	`4`	Passed
boundary redo-caret	`1`	`1`	Passed
normal edit	`[]`	`[]`	Passed
boundary edit	`[]`	`[]`	Passed
normal transaction	`['u1', {'caret': 3, 'text': 'pea', 'value': None}]`	`['u1', {'caret': 3, 'text': 'pea', 'value': None}]`	Passed
boundary transaction	`[{'caret': 0, 'text': '', 'value': ''}]`	`[{'caret': 0, 'text': '', 'value': ''}]`	Passed
normal hover	`['u1']`	`['u1']`	Passed
boundary hover	`[]`	`[]`	Passed
normal redo-divergence	`False`	`False`	Passed
boundary redo-divergence	`True`	`True`	Passed
variant query or selection payload	`pea`	`p`	Failed
unknown completion event	`{'unchanged': True}`	`{'unchanged': True}`	Passed

SHA-256 / 06bd3167e528e47f70d5aada12dcddc17e679f45fe7025746b0746e871a6a105

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 22 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

Stipulated deterministic widget transition model; inputs are validated snapshots. It does not model browser event dispatch, network transport, or linguistic standards. 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 2026-09-29T14:40:42.169433+00:00.

Case digest / eafaec44ed6c3c3b766d590cd7f1b6904f3a6a3600839e3d4f427f2d058586fc