db: Fix downgrades so they match creating from scratch

Fixes #1427.

Author: gnprice

lib/model/database.dart

@@ -135,14 +135,16 @@ class AppDatabase extends _$AppDatabase {
     },
   );
 
+  Future<void> _createLatestSchema(Migrator m) async {
+    await m.createAll();
+    // Corresponds to `from4to5` above.
+    await into(globalSettings).insert(GlobalSettingsCompanion());
+  }
+
   @override
   MigrationStrategy get migration {
     return MigrationStrategy(
-      onCreate: (Migrator m) async {
-        await m.createAll();
-        // Corresponds to `from4to5` above.
-        await into(globalSettings).insert(GlobalSettingsCompanion());
-      },
+      onCreate: _createLatestSchema,
       onUpgrade: (Migrator m, int from, int to) async {
         if (from > to) {
           // This should only ever happen in dev.  As a dev convenience,
@@ -157,7 +159,7 @@ class AppDatabase extends _$AppDatabase {
           assert(to == latestSchemaVersion);
 
           await _dropAll(m);
-          await m.createAll();
+          await _createLatestSchema(m);
           return;
         }
         assert(1 <= from && from <= to && to <= latestSchemaVersion);

test/model/database_test.dart

@@ -147,6 +147,8 @@ void main() {
       // does not have the extra tables and columns.
       final after = AppDatabase(schema.newConnection());
       await verifier.migrateAndValidate(after, toVersion, validateDropped: true);
+      // Check that a custom migration/setup step of ours got run too.
+      check(await after.getGlobalSettings()).themeSetting.isNull();
       await after.close();
     });