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Reassemble message/partial fragments: number order · case 01

Fragments are joined in arrival order instead of by number.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The number order decision evaluates `''.join(g['parts'].values())` where the contract requires `''.join(g['parts'].get(n, '') for n in range(1, total + 1))`.

THE FAILURE

The number order decision evaluates `''.join(g['parts'].values())` where the contract requires `''.join(g['parts'].get(n, '') for n in range(1, total + 1))`.

Unsuccessful approach: Sorting every received number also joins stray numbers beyond the total. The attempted `''.join(g['parts'][n] for n in sorted(g['parts']))` still disagrees with a fixture.

Case contract

fragments {id, number, total (optional), body}. Per id: the first fragment with a given number wins; totals seen on fragments must all agree (otherwise "conflict"); without any total the message is "incomplete"; it is "complete" when every number 1..total is present, and its text joins those numbers in order (other numbers are ignored). Result rows [id, status, text or None] sorted by id.

Why this case matters

Large messages split with message/partial must be reassembled exactly once and in order.

1 / The failure

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

N = 1
observations = []
def solve(fragments):
    groups = {}
    for f in fragments:
        g = groups.setdefault(f['id'], {'totals': [], 'parts': {}})
        if f.get('total') is not None:
            g['totals'].append(f['total'])
        g['parts'].setdefault(f['number'], f['body'])
    out = []
    for pid in sorted(groups):
        g = groups[pid]
        if len(set(g['totals'])) > 1:
            out.append([pid, 'conflict', None])
            continue
        if not g['totals']:
            out.append([pid, 'incomplete', None])
            continue
        total = g['totals'][0]
        if all(n in g['parts'] for n in range(1, total + 1)):
            out.append([pid, 'complete', ''.join(g['parts'].values())])
        else:
            out.append([pid, 'incomplete', None])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD1'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD1']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b1'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '11'}],), [['r', 'complete', '1123']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z1'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one1'}],), [['t', 'complete', 'one1two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z1'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w1', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w1', 'complete', 'solo']])], 2: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD2'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD2']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b2'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '12'}],), [['r', 'complete', '1223']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z2'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one2'}],), [['t', 'complete', 'one2two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z2'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w2', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w2', 'complete', 'solo']])], 3: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD3'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD3']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b3'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '13'}],), [['r', 'complete', '1323']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z3'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one3'}],), [['t', 'complete', 'one3two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z3'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w3', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w3', 'complete', 'solo']])], 4: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD4'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD4']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b4'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '14'}],), [['r', 'complete', '1423']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z4'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one4'}],), [['t', 'complete', 'one4two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z4'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w4', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w4', 'complete', 'solo']])], 5: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD5'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD5']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b5'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '15'}],), [['r', 'complete', '1523']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z5'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one5'}],), [['t', 'complete', 'one5two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z5'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w5', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w5', 'complete', 'solo']])]}
for _label, _args, _expected in _CASES[N]:
    check(_label, solve(*_args), _expected)
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
retransmitted fragment[['p', 'complete', 'ABCD1']][['p', 'complete', 'ABCD1']]Passed
no total yet[['q', 'incomplete', None]][['q', 'incomplete', None]]Passed
repeated equal totals[['r', 'complete', '2311']][['r', 'complete', '1123']]Failed
disagreeing totals[['s', 'conflict', None]][['s', 'conflict', None]]Passed
out of order with stray number[['t', 'complete', 'twojunkone1']][['t', 'complete', 'one1two']]Failed
missing middle with stray[['u', 'incomplete', None]][['u', 'incomplete', None]]Passed
two messages[['v', 'incomplete', None], ['w1', 'complete', 'solo']][['v', 'incomplete', None], ['w1', 'complete', 'solo']]Passed

SHA-256 / 45a629c7d384750e54bb0f884795fca64135490fbfe750b0c4185dcdc5618168

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(fragments):
    groups = {}
    for f in fragments:
        g = groups.setdefault(f['id'], {'totals': [], 'parts': {}})
        if f.get('total') is not None:
            g['totals'].append(f['total'])
        g['parts'].setdefault(f['number'], f['body'])
    out = []
    for pid in sorted(groups):
        g = groups[pid]
        if len(set(g['totals'])) > 1:
            out.append([pid, 'conflict', None])
            continue
        if not g['totals']:
            out.append([pid, 'incomplete', None])
            continue
        total = g['totals'][0]
        if all(n in g['parts'] for n in range(1, total + 1)):
            out.append([pid, 'complete', ''.join(g['parts'][n] for n in sorted(g['parts']))])
        else:
            out.append([pid, 'incomplete', None])
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
_CASES = {1: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD1'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD1']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b1'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '11'}],), [['r', 'complete', '1123']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z1'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one1'}],), [['t', 'complete', 'one1two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z1'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w1', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w1', 'complete', 'solo']])], 2: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD2'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD2']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b2'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '12'}],), [['r', 'complete', '1223']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z2'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one2'}],), [['t', 'complete', 'one2two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z2'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w2', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w2', 'complete', 'solo']])], 3: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD3'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD3']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b3'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '13'}],), [['r', 'complete', '1323']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z3'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one3'}],), [['t', 'complete', 'one3two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z3'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w3', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w3', 'complete', 'solo']])], 4: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD4'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD4']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b4'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '14'}],), [['r', 'complete', '1423']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z4'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one4'}],), [['t', 'complete', 'one4two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z4'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w4', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w4', 'complete', 'solo']])], 5: [('retransmitted fragment', ([{'id': 'p', 'number': 1, 'body': 'AB'}, {'id': 'p', 'number': 2, 'total': 2, 'body': 'CD5'}, {'id': 'p', 'number': 1, 'body': 'XX'}],), [['p', 'complete', 'ABCD5']]), ('no total yet', ([{'id': 'q', 'number': 1, 'body': 'a'}, {'id': 'q', 'number': 2, 'body': 'b5'}],), [['q', 'incomplete', None]]), ('repeated equal totals', ([{'id': 'r', 'number': 2, 'total': 3, 'body': '2'}, {'id': 'r', 'number': 3, 'total': 3, 'body': '3'}, {'id': 'r', 'number': 1, 'body': '15'}],), [['r', 'complete', '1523']]), ('disagreeing totals', ([{'id': 's', 'number': 1, 'total': 3, 'body': 'x'}, {'id': 's', 'number': 2, 'total': 4, 'body': 'y'}, {'id': 's', 'number': 3, 'total': 3, 'body': 'z5'}],), [['s', 'conflict', None]]), ('out of order with stray number', ([{'id': 't', 'number': 2, 'total': 2, 'body': 'two'}, {'id': 't', 'number': 3, 'body': 'junk'}, {'id': 't', 'number': 1, 'body': 'one5'}],), [['t', 'complete', 'one5two']]), ('missing middle with stray', ([{'id': 'u', 'number': 1, 'total': 2, 'body': 'a'}, {'id': 'u', 'number': 5, 'body': 'z5'}],), [['u', 'incomplete', None]]), ('two messages', ([{'id': 'w5', 'number': 1, 'total': 1, 'body': 'solo'}, {'id': 'v', 'number': 1, 'total': 2, 'body': 'half'}],), [['v', 'incomplete', None], ['w5', 'complete', 'solo']])]}
for _label, _args, _expected in _CASES[N]:
    check(_label, solve(*_args), _expected)
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
retransmitted fragment[['p', 'complete', 'ABCD1']][['p', 'complete', 'ABCD1']]Passed
no total yet[['q', 'incomplete', None]][['q', 'incomplete', None]]Passed
repeated equal totals[['r', 'complete', '1123']][['r', 'complete', '1123']]Passed
disagreeing totals[['s', 'conflict', None]][['s', 'conflict', None]]Passed
out of order with stray number[['t', 'complete', 'one1twojunk']][['t', 'complete', 'one1two']]Failed
missing middle with stray[['u', 'incomplete', None]][['u', 'incomplete', None]]Passed
two messages[['v', 'incomplete', None], ['w1', 'complete', 'solo']][['v', 'incomplete', None], ['w1', 'complete', 'solo']]Passed

SHA-256 / 0518221e3b459084024603952b6196fa71f17088c918b5b8208dbe0ca60078d0

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.

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Verification & scope

Stipulated offline model over pre-parsed MIME dictionaries; not a conforming MIME parser, generator or mail client. 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 2026-09-29T14:49:19.110779+00:00.

Case digest / 6d73239cd7edcdc883c8b143968a0eada8ba69cd8fa182be4a76cc3e49c55a9e