Fix `validateDatabaseSchema` in schema tests

drift_dev/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.7.0-dev
+
+- Make `validateDatabaseSchema()` work in migration tests.
+
 ## 2.6.0
 
 - Fix invalid schema verification code being generated for columns with a

drift_dev/lib/api/migrations.dart

@@ -91,10 +91,20 @@ extension VerifySelf on GeneratedDatabase {
 
     final schemaOfThisDatabase = await collectSchemaInput(virtualTables);
 
+    // The expectedSchema expando will store the expected schema for this
+    // database when it's opened in a migration test. This allows this method
+    // to be used in migration tests -- otherwise, this would always compare the
+    // runtime schema to the latest schema from generated code.
+    var referenceSchema = expectedSchema[this];
+
+    if (referenceSchema == null) {
       // Collect the schema how it would be if we just called `createAll` on a
       // clean database.
       final referenceDb = _GenerateFromScratch(this, NativeDatabase.memory());
-    final referenceSchema = await referenceDb.collectSchemaInput(virtualTables);
+      referenceSchema = expectedSchema[this] ??
+          await referenceDb.collectSchemaInput(virtualTables);
+      await referenceDb.close();
+    }
 
     verify(referenceSchema, schemaOfThisDatabase, validateDropped);
   }

drift_dev/lib/src/services/schema/verifier_impl.dart

@@ -7,6 +7,8 @@ import 'package:sqlite3/sqlite3.dart';
 
 import 'find_differences.dart';
 
+Expando<List<Input>> expectedSchema = Expando();
+
 class VerifierImplementation implements SchemaVerifier {
   final SchemaInstantiationHelper helper;
   final Random _random = Random();
@@ -21,18 +23,22 @@ class VerifierImplementation implements SchemaVerifier {
         if (table is VirtualTableInfo) table.entityName,
     ];
 
-    // Open the database to collect its schema. Put a delegate in between
+    // Open a connection to instantiate and extract the reference schema.
-    // claiming that the actual version is what we expect.
-    await db.executor.ensureOpen(_DelegatingUser(expectedVersion, db));
-    final actualSchema = await db.executor.collectSchemaInput(virtualTables);
-
-    // Open another connection to instantiate and extract the reference schema.
     final otherConnection = await startAt(expectedVersion);
     await otherConnection.executor.ensureOpen(_DelegatingUser(expectedVersion));
     final referenceSchema =
         await otherConnection.executor.collectSchemaInput(virtualTables);
     await otherConnection.executor.close();
 
+    // Attach the reference schema to the database so that VerifySelf.validateDatabaseSchema
+    // works
+    expectedSchema[db] = referenceSchema;
+
+    // Open the database to collect its schema. Put a delegate in between
+    // claiming that the actual version is what we expect.
+    await db.executor.ensureOpen(_DelegatingUser(expectedVersion, db));
+    final actualSchema = await db.executor.collectSchemaInput(virtualTables);
+
     verify(referenceSchema, actualSchema, validateDropped);
   }
 

examples/app/lib/database/connection/native.dart

@@ -2,6 +2,8 @@ import 'dart:io';
 
 import 'package:drift/drift.dart';
 import 'package:drift/native.dart';
+import 'package:drift_dev/api/migrations.dart';
+import 'package:flutter/foundation.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:path/path.dart' as p;
 
@@ -18,3 +20,17 @@ DatabaseConnection connect() {
     return NativeDatabase.createBackgroundConnection(await databaseFile);
   }));
 }
+
+Future<void> validateDatabaseSchema(GeneratedDatabase database) async {
+  // This method validates that the actual schema of the opened database matches
+  // the tables, views, triggers and indices for which drift_dev has generated
+  // code.
+  // Validating the database's schema after opening it is generally a good idea,
+  // since it allows us to get an early warning if we change a table definition
+  // without writing a schema migration for it.
+  //
+  // For details, see: https://drift.simonbinder.eu/docs/advanced-features/migrations/#verifying-a-database-schema-at-runtime
+  if (kDebugMode) {
+    await VerifySelf(database).validateDatabaseSchema();
+  }
+}

examples/app/lib/database/connection/unsupported.dart

@@ -1,6 +1,17 @@
 import 'package:drift/drift.dart';
 
-DatabaseConnection connect() {
+Never _unsupported() {
   throw UnsupportedError(
       'No suitable database implementation was found on this platform.');
 }
+
+// Depending on the platform the app is compiled to, the following stubs will
+// be replaced with the methods in native.dart or web.dart
+
+DatabaseConnection connect() {
+  _unsupported();
+}
+
+Future<void> validateDatabaseSchema(GeneratedDatabase database) async {
+  _unsupported();
+}

examples/app/lib/database/connection/web.dart

@@ -36,3 +36,10 @@ DatabaseConnection connect({bool isInWebWorker = false}) {
     }));
   }
 }
+
+Future<void> validateDatabaseSchema(GeneratedDatabase database) async {
+  // Unfortunately, validating database schemas only works for native platforms
+  // right now.
+  // As we also have migration tests (see the `Testing migrations` section in
+  // the readme of this example), this is not a huge issue.
+}

examples/app/lib/database/database.dart

@@ -63,6 +63,11 @@ class AppDatabase extends _$AppDatabase {
             ]);
           });
         }
+
+        // This follows the recommendation to validate that the database schema
+        // matches what drift expects (https://drift.simonbinder.eu/docs/advanced-features/migrations/#verifying-a-database-schema-at-runtime).
+        // It allows catching bugs in the migration logic early.
+        await impl.validateDatabaseSchema(this);
       },
     );
   }

examples/app/pubspec.yaml

@@ -11,6 +11,7 @@ dependencies:
   flutter:
     sdk: flutter
   drift:
+  drift_dev:
   file_picker: ^5.2.5
   flutter_colorpicker: ^1.0.3
   flutter_riverpod: ^2.3.0
@@ -35,7 +36,6 @@ dev_dependencies:
   # `build.yaml`.
   build_web_compilers: ^3.2.2
   build: ^2.2.1
-  drift_dev:
 
 flutter:
   uses-material-design: true

examples/migrations_example/lib/database.dart

@@ -1,4 +1,5 @@
 import 'package:drift/drift.dart';
+import 'package:drift_dev/api/migrations.dart';
 
 import 'tables.dart';
 import 'src/generated/schema_v2.dart' as v2;
@@ -72,6 +73,11 @@ class Database extends _$Database {
           }
         }
       },
+      beforeOpen: (details) async {
+        // For Flutter apps, this should be wrapped in an if (kDebugMode) as
+        // suggested here: https://drift.simonbinder.eu/docs/advanced-features/migrations/#verifying-a-database-schema-at-runtime
+        await validateDatabaseSchema();
+      },
     );
   }
 }

examples/migrations_example/pubspec.yaml

@@ -7,9 +7,9 @@ environment:
 
 dependencies:
   drift:
+  drift_dev:
 
 dev_dependencies:
   lints: ^2.0.0
-  drift_dev:
   build_runner: ^2.0.0
   test: ^1.15.4