Proper ts/mtime setting and tracking. Added Kanta.mtime property for reading current change time.

tests/test_mtime.py

@@ -0,0 +1,143 @@
+"""Tests for mtime handling and the public ``kanta.mtime`` property."""
+
+from datetime import UTC, datetime
+
+import pytest
+
+from kanta import ChangeRecord
+
+from .support import Data, make_kanta, seed_single_change
+
+
+def _read_last_change(path, format_config):
+    name, serializer_cls = format_config
+    serializer = serializer_cls()
+    framer = serializer.framer_cls()
+    last = None
+    for is_snapshot, payload, _, _ in framer.iter_records(path.read_bytes(), 0):
+        if is_snapshot:
+            continue
+        last = serializer.decode(payload, type=ChangeRecord)
+    assert last is not None
+    return last
+
+
+@pytest.mark.asyncio
+async def test_default_transaction_updates_mtime(tmp_path, format_config):
+    path = tmp_path / "test.db"
+    kanta = make_kanta(path, Data, format_config)
+    await kanta.open()
+
+    before = datetime.now(UTC)
+    with kanta.transaction(action="inc") as data:
+        data.counter = 1
+    await kanta.flush()
+    await kanta.close()
+
+    rec = _read_last_change(path, format_config)
+    assert rec.ts == rec.m
+    assert before <= rec.m <= datetime.now(UTC)
+    assert kanta.mtime == rec.m
+
+
+@pytest.mark.asyncio
+async def test_transaction_custom_mtime(tmp_path, format_config):
+    path = tmp_path / "test.db"
+    kanta = make_kanta(path, Data, format_config)
+    await kanta.open()
+
+    custom_m = datetime(2026, 1, 1, 8, 0, tzinfo=UTC)
+    with kanta.transaction(action="inc", mtime=custom_m) as data:
+        data.counter = 1
+    await kanta.flush()
+    await kanta.close()
+
+    rec = _read_last_change(path, format_config)
+    assert rec.m == custom_m
+    assert kanta.mtime == custom_m
+
+
+@pytest.mark.asyncio
+async def test_transaction_mtime_false_preserves_mtime(tmp_path, format_config):
+    path = tmp_path / "test.db"
+    kanta = make_kanta(path, Data, format_config)
+    await kanta.open()
+
+    first_m = datetime(2026, 1, 1, 10, 0, tzinfo=UTC)
+    with kanta.transaction(action="first", mtime=first_m) as data:
+        data.counter = 1
+
+    with kanta.transaction(action="second", mtime=False) as data:
+        data.counter = 2
+
+    await kanta.flush()
+    await kanta.close()
+
+    records = []
+    name, serializer_cls = format_config
+    serializer = serializer_cls()
+    framer = serializer.framer_cls()
+    for is_snapshot, payload, _, _ in framer.iter_records(path.read_bytes(), 0):
+        if is_snapshot:
+            continue
+        records.append(serializer.decode(payload, type=ChangeRecord))
+
+    assert records[0].m == first_m
+    assert records[1].m is None
+    assert kanta.mtime == first_m
+
+
+@pytest.mark.asyncio
+async def test_migration_does_not_update_mtime(tmp_path, format_config):
+    path = tmp_path / "test.db"
+    seed_m = datetime(2025, 12, 31, 23, 0, tzinfo=UTC)
+    seed_single_change(
+        path,
+        ChangeRecord(
+            ts=seed_m,
+            m=seed_m,
+            a="seed",
+            v=0,
+            diff={"counter": 0},
+        ),
+        format_config,
+    )
+
+    kanta = make_kanta(path, Data, format_config)
+    await kanta.open()
+
+    assert kanta.mtime == seed_m
+
+    new_m = datetime(2026, 1, 5, 10, 0, tzinfo=UTC)
+    with kanta.transaction(action="inc", mtime=new_m) as data:
+        data.counter = 5
+    await kanta.flush()
+
+    assert kanta.mtime == new_m
+    await kanta.close()
+
+
+@pytest.mark.asyncio
+async def test_rollback_does_not_update_mtime(tmp_path, format_config):
+    path = tmp_path / "test.db"
+    kanta = make_kanta(path, Data, format_config)
+    await kanta.open()
+
+    seed_m = datetime(2026, 1, 1, 10, 0, tzinfo=UTC)
+    with kanta.transaction(action="seed", mtime=seed_m) as data:
+        data.counter = 1
+
+    before = kanta.mtime
+
+    try:
+        with kanta.transaction(
+            action="boom", mtime=datetime(2099, 1, 1, tzinfo=UTC)
+        ) as data:
+            data.counter = 99
+            raise RuntimeError("fail")
+    except RuntimeError:
+        pass
+
+    assert kanta.data.counter == 1
+    assert kanta.mtime == before
+    await kanta.close()