Fix creation of new database, ensuring that a bootstrap record of the initial state is always written.

tests/support.py

@@ -70,6 +70,18 @@ def change_actions(path: Path, format_config) -> list[str]:
     return actions
 
 
+def read_changes(path: Path, format_config) -> list[ChangeRecord]:
+    _, serializer_cls = format_config
+    serializer = serializer_cls()
+    framer = serializer.framer_cls()
+    records: list[ChangeRecord] = []
+    for is_snapshot, payload, _, _ in framer.iter_records(path.read_bytes(), 0):
+        if is_snapshot:
+            continue
+        records.append(serializer.decode(payload, type=ChangeRecord))
+    return records
+
+
 def make_migrations_module(name: str, fn_name: str, fn):
     mod = ModuleType(name)
     mod.__dict__[fn_name] = fn

tests/test_kanta_integration.py

@@ -17,6 +17,7 @@ from .support import (
     change_actions,
     fixed_change,
     make_kanta,
+    read_changes,
     seed_single_change,
 )
 
@@ -30,6 +31,44 @@ async def test_load_empty(tmp_path, format_config):
     await kanta.close()
 
 
+@pytest.mark.asyncio
+async def test_new_file_writes_bootstrap_record_without_handlers(
+    tmp_path, format_config
+):
+    path = tmp_path / "test.db"
+    kanta = make_kanta(path, Data, format_config)
+    await kanta.open()
+    await kanta.close()
+
+    records = read_changes(path, format_config)
+    assert len(records) == 1
+    assert records[0].a == "bootstrap"
+    assert records[0].diff == {"$replace": {"users": {}, "counter": 0}}
+
+
+@pytest.mark.asyncio
+async def test_new_file_persists_initial_state_for_roundtrip(tmp_path, format_config):
+    path = tmp_path / "test.db"
+    kanta = make_kanta(
+        path, Data(counter=5, users={"alice": User(name="Alice")}), format_config
+    )
+    await kanta.open()
+    await kanta.close()
+
+    records = read_changes(path, format_config)
+    assert len(records) == 1
+    assert records[0].a == "bootstrap"
+    assert records[0].diff == {
+        "$replace": {"users": {"alice": {"name": "Alice", "age": 0}}, "counter": 5}
+    }
+
+    kanta2 = make_kanta(path, Data, format_config)
+    await kanta2.open()
+    assert kanta2.data.counter == 5
+    assert kanta2.data.users["alice"].name == "Alice"
+    await kanta2.close()
+
+
 @pytest.mark.asyncio
 async def test_open_overwrites_caller_owned_root_data(tmp_path, format_config):
     path = tmp_path / "test.db"

tests/test_mtime.py

@@ -82,8 +82,9 @@ async def test_transaction_mtime_false_preserves_mtime(tmp_path, format_config):
             continue
         records.append(serializer.decode(payload, type=ChangeRecord))
 
-    assert records[0].m == first_m
-    assert records[1].m is None
+    assert records[0].a == "bootstrap"
+    assert records[1].m == first_m
+    assert records[2].m is None
     assert kanta.mtime == first_m