Disallow zero as a schema version (#2469)

drift/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.8.3-dev
+
+- Forbid `schemaVersion` returning `0`, as this causes issues in the migrator.
+
 ## 2.8.2
 
 - Fix prepared statements leaking when the statement cache is disabled.

drift/lib/src/runtime/api/db_base.dart

@@ -20,6 +20,9 @@ abstract class GeneratedDatabase extends DatabaseConnectionUser
 
   /// Specify the schema version of your database. Whenever you change or add
   /// tables, you should bump this field and provide a [migration] strategy.
+  ///
+  /// The [schemaVersion] must be positive. Typically, one starts with a value
+  /// of `1` and increments the value for each modification to the schema.
   @override
   int get schemaVersion;
 
@@ -110,6 +113,14 @@ abstract class GeneratedDatabase extends DatabaseConnectionUser
   @nonVirtual
   Future<void> beforeOpen(QueryExecutor executor, OpeningDetails details) {
     return _runConnectionZoned(BeforeOpenRunner(this, executor), () async {
+      if (schemaVersion <= 0) {
+        throw StateError(
+          'The schemaVersion of your database must be positive. \n'
+          "A value of zero can't be distinguished from an uninitialized "
+          'database, which causes issues in the migrator',
+        );
+      }
+
       if (details.wasCreated) {
         final migrator = createMigrator();
         await _resolvedMigration.onCreate(migrator);

drift/test/database/database_test.dart

@@ -110,4 +110,15 @@ void main() {
     verify(ex2.runSelect('SELECT 1', []));
     verifyNever(ex2.runSelect(any, any));
   });
+
+  test('disallows zero as a schema version', () async {
+    var db = TodoDb(MockExecutor(OpeningDetails(null, 0)))..schemaVersion = 0;
+    await expectLater(db.customSelect('SELECT 1').get(), throwsStateError);
+
+    db = TodoDb(MockExecutor(OpeningDetails(null, 0)))..schemaVersion = -1;
+    await expectLater(db.customSelect('SELECT 1').get(), throwsStateError);
+
+    db = TodoDb(MockExecutor(OpeningDetails(null, 0)))..schemaVersion = 1;
+    await expectLater(db.customSelect('SELECT 1').get(), completes);
+  });
 }