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FA-75661 / Text diff and three-way merge / Open access

Three-way key-value merge: matching edits on both branches are a conflict · case 01

Both branches set the same new value and the merge still reports a conflict.

Verified by executionVariant 1 · 10 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The first check for agreement between ours and theirs is missing.

THE FAILURE

The first check for agreement between ours and theirs is missing.

Unsuccessful approach: Excluding agreement on absence still reports a conflict when both sides deleted the key.

Case contract

Merge base, ours and theirs maps key by key over the union of keys; an absent key and a key holding null are different states. If ours and theirs agree, take that state; else if ours equals base take theirs; else if theirs equals base take ours; otherwise record a conflict and keep ours. Return sorted merged [key, value] pairs and sorted conflicting keys.

Why this case matters

Structured configuration and lock files are merged per key, where deletions and null values must stay distinguishable.

1 / The failure

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

N = 1
observations = []
def solve(base, ours, theirs):
    MISSING = object()
    merged, conflicts = {}, []
    for k in sorted(set(base) | set(ours) | set(theirs)):
        b = base.get(k, MISSING)
        o = ours.get(k, MISSING)
        t = theirs.get(k, MISSING)
        if o == b:
            r = t
        elif t == b:
            r = o
        else:
            conflicts.append(k)
            r = o
        if r is not MISSING:
            merged[k] = r
    return {'merged': sorted([k, v] for k, v in merged.items()), 'conflicts': conflicts}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = {
    1: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '81', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '81']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z1'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z1'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e1'}], {'merged': [['extra', 'e1'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm1'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm1'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    2: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '82', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '82']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z2'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z2'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e2'}], {'merged': [['extra', 'e2'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm2'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm2'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    3: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '83', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '83']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z3'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z3'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e3'}], {'merged': [['extra', 'e3'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm3'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm3'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    4: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '84', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '84']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z4'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z4'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e4'}], {'merged': [['extra', 'e4'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm4'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm4'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    5: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '85', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '85']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z5'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z5'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e5'}], {'merged': [['extra', 'e5'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm5'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm5'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
}[N]
for label, args, expected in cases:
    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
each side changes a different key{'conflicts': [], 'merged': [['host', 'b'], ['mode', 'x'], ['port', '81']]}{'conflicts': [], 'merged': [['host', 'b'], ['mode', 'x'], ['port', '81']]}Passed
both change a key the same way{'conflicts': ['mode'], 'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']]}Failed
both delete the same key{'conflicts': ['mode'], 'merged': [['host', 'a'], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['port', '80']]}Failed
conflicting changes keep ours{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']]}{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']]}Passed
delete versus modify conflicts{'conflicts': ['mode'], 'merged': [['host', 'a'], ['mode', 'z1'], ['port', '80']]}{'conflicts': ['mode'], 'merged': [['host', 'a'], ['mode', 'z1'], ['port', '80']]}Passed
explicit null differs from deletion{'conflicts': [], 'merged': [['host', 'a'], ['mode', None], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['mode', None], ['port', '80']]}Passed
key added only by theirs{'conflicts': [], 'merged': [['extra', 'e1'], ['host', 'a'], ['mode', 'x'], ['port', '80']]}{'conflicts': [], 'merged': [['extra', 'e1'], ['host', 'a'], ['mode', 'x'], ['port', '80']]}Passed
key added only by ours{'conflicts': [], 'merged': [['host', 'a'], ['mine', 'm1'], ['mode', 'x'], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['mine', 'm1'], ['mode', 'x'], ['port', '80']]}Passed
modify versus delete conflicts{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x']]}{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x']]}Passed
null in base and deleted by ours{'conflicts': [], 'merged': [['j', '2']]}{'conflicts': [], 'merged': [['j', '2']]}Passed

SHA-256 / 7d73bc88bc9dbfe18a731d14195c94e99a66ce6004d42733fef565f2ce9863c0

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(base, ours, theirs):
    MISSING = object()
    merged, conflicts = {}, []
    for k in sorted(set(base) | set(ours) | set(theirs)):
        b = base.get(k, MISSING)
        o = ours.get(k, MISSING)
        t = theirs.get(k, MISSING)
        if o == t and o is not MISSING:
            r = o
        elif o == b:
            r = t
        elif t == b:
            r = o
        else:
            conflicts.append(k)
            r = o
        if r is not MISSING:
            merged[k] = r
    return {'merged': sorted([k, v] for k, v in merged.items()), 'conflicts': conflicts}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = {
    1: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '81', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '81']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z1'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z1'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e1'}], {'merged': [['extra', 'e1'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm1'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm1'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    2: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '82', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '82']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z2'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z2'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e2'}], {'merged': [['extra', 'e2'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm2'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm2'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    3: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '83', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '83']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z3'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z3'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e3'}], {'merged': [['extra', 'e3'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm3'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm3'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    4: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '84', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '84']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z4'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z4'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e4'}], {'merged': [['extra', 'e4'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm4'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm4'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
    5: [('each side changes a different key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'b', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '85', 'mode': 'x'}], {'merged': [['host', 'b'], ['mode', 'x'], ['port', '85']], 'conflicts': []}), ('both change a key the same way', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'y'}, {'host': 'a', 'port': '80', 'mode': 'y'}], {'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']], 'conflicts': []}), ('both delete the same key', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['port', '80']], 'conflicts': []}), ('conflicting changes keep ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '1', 'mode': 'x'}, {'host': 'a', 'port': '2', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']], 'conflicts': ['port']}), ('delete versus modify conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'z5'}, {'host': 'a', 'port': '80'}], {'merged': [['host', 'a'], ['mode', 'z5'], ['port', '80']], 'conflicts': ['mode']}), ('explicit null differs from deletion', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': None}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', None], ['port', '80']], 'conflicts': []}), ('key added only by theirs', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'extra': 'e5'}], {'merged': [['extra', 'e5'], ['host', 'a'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('key added only by ours', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'port': '80', 'mode': 'x', 'mine': 'm5'}, {'host': 'a', 'port': '80', 'mode': 'x'}], {'merged': [['host', 'a'], ['mine', 'm5'], ['mode', 'x'], ['port', '80']], 'conflicts': []}), ('modify versus delete conflicts', [{'host': 'a', 'port': '80', 'mode': 'x'}, {'host': 'a', 'mode': 'x'}, {'host': 'a', 'port': '443', 'mode': 'x'}], {'merged': [['host', 'a'], ['mode', 'x']], 'conflicts': ['port']}), ('null in base and deleted by ours', [{'k': None, 'j': '1'}, {'j': '1'}, {'k': None, 'j': '2'}], {'merged': [['j', '2']], 'conflicts': []})],
}[N]
for label, args, expected in cases:
    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
each side changes a different key{'conflicts': [], 'merged': [['host', 'b'], ['mode', 'x'], ['port', '81']]}{'conflicts': [], 'merged': [['host', 'b'], ['mode', 'x'], ['port', '81']]}Passed
both change a key the same way{'conflicts': [], 'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['mode', 'y'], ['port', '80']]}Passed
both delete the same key{'conflicts': ['mode'], 'merged': [['host', 'a'], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['port', '80']]}Failed
conflicting changes keep ours{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']]}{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x'], ['port', '1']]}Passed
delete versus modify conflicts{'conflicts': ['mode'], 'merged': [['host', 'a'], ['mode', 'z1'], ['port', '80']]}{'conflicts': ['mode'], 'merged': [['host', 'a'], ['mode', 'z1'], ['port', '80']]}Passed
explicit null differs from deletion{'conflicts': [], 'merged': [['host', 'a'], ['mode', None], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['mode', None], ['port', '80']]}Passed
key added only by theirs{'conflicts': [], 'merged': [['extra', 'e1'], ['host', 'a'], ['mode', 'x'], ['port', '80']]}{'conflicts': [], 'merged': [['extra', 'e1'], ['host', 'a'], ['mode', 'x'], ['port', '80']]}Passed
key added only by ours{'conflicts': [], 'merged': [['host', 'a'], ['mine', 'm1'], ['mode', 'x'], ['port', '80']]}{'conflicts': [], 'merged': [['host', 'a'], ['mine', 'm1'], ['mode', 'x'], ['port', '80']]}Passed
modify versus delete conflicts{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x']]}{'conflicts': ['port'], 'merged': [['host', 'a'], ['mode', 'x']]}Passed
null in base and deleted by ours{'conflicts': [], 'merged': [['j', '2']]}{'conflicts': [], 'merged': [['j', '2']]}Passed

SHA-256 / 70a58a3441a5c1f1bb6b543ac9560e04983f101e17d9f677cfd61a3c52da6e02

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 10 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.

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Verification & scope

A deterministic, bounded teaching model of one diff, patch or merge rule with stipulated conventions; it is not a production diff or version-control implementation and makes no claim of conformance to any specific tool. 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 2026-09-29T14:49:09.032107+00:00.

Case digest / ca17c034fd1b10e04a1bd1a4c6032e3494110aa0918ea4340bb52369a27fb6ed