New migrations system, ported from sqlite-migrate (#754)

Closes #752

tests/test_migrations.py

@@ -0,0 +1,110 @@
+import pytest
+import sqlite_utils
+from sqlite_utils import Migrations
+
+
+@pytest.fixture
+def migrations():
+    migrations = Migrations("test")
+
+    @migrations()
+    def m001(db):
+        db["dogs"].insert({"name": "Cleo"})
+
+    @migrations()
+    def m002(db):
+        db["cats"].create({"name": str})
+        db.query("insert into dogs (name) values ('Pancakes')")
+
+    return migrations
+
+
+@pytest.fixture
+def migrations_not_ordered_alphabetically():
+    # Names order alphabetically in the wrong direction but this
+    # should still be applied correctly.
+    migrations = Migrations("test")
+
+    @migrations()
+    def m002(db):
+        db["dogs"].insert({"name": "Cleo"})
+
+    @migrations()
+    def m001(db):
+        db["cats"].create({"name": str})
+        db.query("insert into dogs (name) values ('Pancakes')")
+
+    return migrations
+
+
+@pytest.fixture
+def migrations2():
+    migrations = Migrations("test2")
+
+    @migrations()
+    def m001(db):
+        db["dogs2"].insert({"name": "Cleo"})
+
+    return migrations
+
+
+def test_basic(migrations):
+    db = sqlite_utils.Database(memory=True)
+    assert db.table_names() == []
+    migrations.apply(db)
+    assert set(db.table_names()) == {"_sqlite_migrations", "dogs", "cats"}
+
+
+def test_stop_before(migrations):
+    db = sqlite_utils.Database(memory=True)
+    assert db.table_names() == []
+    migrations.apply(db, stop_before="m002")
+    assert set(db.table_names()) == {"_sqlite_migrations", "dogs"}
+    migrations.apply(db)
+    assert set(db.table_names()) == {"_sqlite_migrations", "dogs", "cats"}
+
+
+def test_two_migration_sets(migrations, migrations2):
+    db = sqlite_utils.Database(memory=True)
+    assert db.table_names() == []
+    migrations.apply(db)
+    migrations2.apply(db)
+    assert set(db.table_names()) == {"_sqlite_migrations", "dogs", "cats", "dogs2"}
+
+
+def test_order_does_not_matter(migrations, migrations_not_ordered_alphabetically):
+    db1 = sqlite_utils.Database(memory=True)
+    db2 = sqlite_utils.Database(memory=True)
+    migrations.apply(db1)
+    migrations_not_ordered_alphabetically.apply(db2)
+    assert db1.schema == db2.schema
+
+
+@pytest.mark.parametrize(
+    "create_table,pk",
+    (
+        (
+            {
+                "migration_set": str,
+                "name": str,
+                "applied_at": str,
+            },
+            "name",
+        ),
+        (
+            {
+                "migration_set": str,
+                "name": str,
+                "applied_at": str,
+            },
+            ("migration_set", "name"),
+        ),
+    ),
+)
+def test_upgrades_sqlite_migrations(migrations, create_table, pk):
+    db = sqlite_utils.Database(memory=True)
+    db["_sqlite_migrations"].create(create_table, pk=pk)
+    assert db.table_names() == ["_sqlite_migrations"]
+    assert db["_sqlite_migrations"].pks == ([pk] if isinstance(pk, str) else list(pk))
+    migrations.apply(db)
+    assert db["_sqlite_migrations"].pks == ["id"]