Add failing test.

Author: rkistner

test/basic_test.dart

@@ -368,6 +368,30 @@ void main() {
       expect(await savedTx!.getAutoCommit(), equals(true));
       expect(savedTx!.closed, equals(true));
     });
+
+    test('closing', () async {
+      // Test race condition in SqliteConnectionPool:
+      // 1. Open two concurrent queries, which opens two connection.
+      // 2. Second connection takes longer to open than first.
+      // 3. Call db.close().
+      // 4. Now second connection is ready. Second query has two connections to choose from.
+      // 5. However, first connection is closed, so it's removed from the pool.
+      // 6. Triggers `Concurrent modification during iteration: Instance(length:1) of '_GrowableList'`
+
+      final db =
+          SqliteDatabase.withFactory(testFactory(path: path, initStatements: [
+        // Second connection to sleep more than first connection
+        'SELECT test_sleep(test_connection_number() * 10)'
+      ]));
+      await createTables(db);
+
+      final future1 = db.get('SELECT test_sleep(10) as sleep');
+      final future2 = db.get('SELECT test_sleep(10) as sleep');
+      final closeFuture = db.close();
+      await closeFuture;
+      await future1;
+      await future2;
+    });
   });
 }
 

test/util.dart

@@ -14,11 +14,13 @@ const defaultSqlitePath = 'libsqlite3.so.0';
 
 class TestSqliteOpenFactory extends DefaultSqliteOpenFactory {
   String sqlitePath;
+  List<String> initStatements;
 
   TestSqliteOpenFactory(
       {required super.path,
       super.sqliteOptions,
-      this.sqlitePath = defaultSqlitePath});
+      this.sqlitePath = defaultSqlitePath,
+      this.initStatements = const []});
 
   @override
   sqlite.Database open(SqliteOpenOptions options) {
@@ -45,12 +47,29 @@ class TestSqliteOpenFactory extends DefaultSqliteOpenFactory {
       },
     );
 
+    db.createFunction(
+      functionName: 'test_connection_number',
+      argumentCount: const sqlite.AllowedArgumentCount(0),
+      function: (args) {
+        // write: 0, read: 1 - 5
+        final name = Isolate.current.debugName ?? '-0';
+        var nr = name.split('-').last;
+        return int.tryParse(nr) ?? 0;
+      },
+    );
+
+    for (var s in initStatements) {
+      db.execute(s);
+    }
+
     return db;
   }
 }
 
-SqliteOpenFactory testFactory({String? path}) {
-  return TestSqliteOpenFactory(path: path ?? dbPath());
+SqliteOpenFactory testFactory(
+    {String? path, List<String> initStatements = const []}) {
+  return TestSqliteOpenFactory(
+      path: path ?? dbPath(), initStatements: initStatements);
 }
 
 Future<SqliteDatabase> setupDatabase({String? path}) async {