FA-7956 / Selection controls / Open access

Anchored range selection: Clicking a removed item clears a valid selection · case 01

Clicking a removed item clears a valid selection.

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

ROOT CAUSE

The missing target operation uses `return []` where the contract requires `return sorted(selected)`.

THE FAILURE

The missing target operation uses `return []` where the contract requires `return sorted(selected)`.

Unsuccessful approach: Adding a removed target introduces a nonexistent selection.

Case contract

Ranges include both endpoints in document order; plain clicks replace; additive selection unions; missing targets preserve selection.

Why this case matters

A deterministic model of anchored range selection; this isolates one interface invariant without requiring a browser.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(items, selected, anchor, target, extend, additive):
    if target not in items: return []
    if not extend or anchor not in items: span = {target}
    else:
        a, b = sorted((items.index(anchor), items.index(target)))
        span = set(items[a:b+1])
    return sorted(set(selected) | span if additive else span)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('removed', solve(['a','b'], ['a'], 'a', 'x', False, False), ['a'])
check('plain', solve(['a','b','c'], ['a'], 'a', 'c', False, False), ['c'])
check('forward', solve(['a','b','c'], [], 'a', 'c', True, False), ['a', 'b', 'c'])
check('backward', solve(['a','b','c'], [], 'c', 'a', True, False), ['a', 'b', 'c'])
check('union', solve(['a','b','c'], ['a'], 'b', 'c', True, True), ['a', 'b', 'c'])
check('replace', solve(['a','b','c'], ['a'], 'b', 'c', True, False), ['b', 'c'])
check('parameterized inclusive range', solve(list(range(N+2)), [], 0, N, True, False), list(range(N+1)))
for repetition in range(N):
    check('repeat replace', solve(['a','b','c'], ['a'], 'b', 'c', True, False), ['b', 'c'])
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
removed	`[]`	`['a']`	Failed
plain	`['c']`	`['c']`	Passed
forward	`['a', 'b', 'c']`	`['a', 'b', 'c']`	Passed
backward	`['a', 'b', 'c']`	`['a', 'b', 'c']`	Passed
union	`['a', 'b', 'c']`	`['a', 'b', 'c']`	Passed
replace	`['b', 'c']`	`['b', 'c']`	Passed
parameterized inclusive range	`[0, 1]`	`[0, 1]`	Passed
repeat replace	`['b', 'c']`	`['b', 'c']`	Passed

SHA-256 / a6af63f73a0d88dcbb4ec9112bcc112a509d5d1c82f78f7ba24d15bff409a10a

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(items, selected, anchor, target, extend, additive):
    if target not in items: return sorted(set(selected) | {target})
    if not extend or anchor not in items: span = {target}
    else:
        a, b = sorted((items.index(anchor), items.index(target)))
        span = set(items[a:b+1])
    return sorted(set(selected) | span if additive else span)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('removed', solve(['a','b'], ['a'], 'a', 'x', False, False), ['a'])
check('plain', solve(['a','b','c'], ['a'], 'a', 'c', False, False), ['c'])
check('forward', solve(['a','b','c'], [], 'a', 'c', True, False), ['a', 'b', 'c'])
check('backward', solve(['a','b','c'], [], 'c', 'a', True, False), ['a', 'b', 'c'])
check('union', solve(['a','b','c'], ['a'], 'b', 'c', True, True), ['a', 'b', 'c'])
check('replace', solve(['a','b','c'], ['a'], 'b', 'c', True, False), ['b', 'c'])
check('parameterized inclusive range', solve(list(range(N+2)), [], 0, N, True, False), list(range(N+1)))
for repetition in range(N):
    check('repeat replace', solve(['a','b','c'], ['a'], 'b', 'c', True, False), ['b', 'c'])
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
removed	`['a', 'x']`	`['a']`	Failed
plain	`['c']`	`['c']`	Passed
forward	`['a', 'b', 'c']`	`['a', 'b', 'c']`	Passed
backward	`['a', 'b', 'c']`	`['a', 'b', 'c']`	Passed
union	`['a', 'b', 'c']`	`['a', 'b', 'c']`	Passed
replace	`['b', 'c']`	`['b', 'c']`	Passed
parameterized inclusive range	`[0, 1]`	`[0, 1]`	Passed
repeat replace	`['b', 'c']`	`['b', 'c']`	Passed

SHA-256 / f290219bc4204b39e9216ae96d61ad77ce08255ec741e604209c645253705e35

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

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 2026-09-29T14:38:17.048216+00:00.

Case digest / 6f4e30105e40657666ee6903060695e4c26c761857982bbb3d8162de45ac6b6e