feat: createFunction async method implemented

lib/sqlite3_async.dart

@@ -8,6 +8,8 @@ import 'package:logging/logging.dart';
 import 'package:logging_appenders/logging_appenders.dart';
 import 'package:sqlite3/sqlite3.dart';
 
+export 'package:sqlite3/sqlite3.dart' show AllowedArgumentCount;
+
 /// An opened sqlite3 database with async methods.
 class AsyncDatabase {
   static final Logger _log = Logger((AsyncDatabase).toString());
@@ -80,6 +82,24 @@ class AsyncDatabase {
         body: _StatementParams(sql, parameters));
   }
 
+  // Register a custom function we can invoke from sql
+  Future<void> createFunction({
+    required String functionName,
+    required ScalarFunction function,
+    AllowedArgumentCount argumentCount = const AllowedArgumentCount.any(),
+    bool deterministic = false,
+    bool directOnly = true,
+  }) async {
+    return await _sendCommand("createFunction",
+        body: _CreateFunctionParams(
+          functionName: functionName,
+          function: function,
+          argumentCount: argumentCount,
+          deterministic: deterministic,
+          directOnly: directOnly,
+        ));
+  }
+
   /// Closes this database and releases associated resources.
   Future<void> dispose() async {
     await _sendCommand("dispose");
@@ -115,6 +135,9 @@ class AsyncDatabase {
           case "select":
             _selectSync(db!, cmd, ourReceivePort);
             break;
+          case "createFunction":
+            _createFunctionSync(db!, cmd, ourReceivePort);
+            break;
           case "dispose":
             _disposeSync(db!, cmd, ourReceivePort);
             break;
@@ -172,6 +195,19 @@ class AsyncDatabase {
         body: version));
   }
 
+  static void _createFunctionSync(
+      Database db, _AsyncDatabaseCommand cmd, ReceivePort ourReceivePort) {
+    _CreateFunctionParams params = cmd.body;
+    db.createFunction(
+      functionName: params.functionName,
+      function: params.function,
+      argumentCount: params.argumentCount,
+      deterministic: params.deterministic,
+      directOnly: params.directOnly,
+    );
+    cmd.sendPort.send(_AsyncDatabaseCommand(cmd.type, ourReceivePort.sendPort));
+  }
+
   static Database _openSync(
       _AsyncDatabaseCommand cmd, ReceivePort ourReceivePort) {
     _OpenDatabaseParams params = cmd.body;
@@ -226,3 +262,20 @@ class _StatementParams {
 
   const _StatementParams(this.sql, this.parameters);
 }
+
+@immutable
+class _CreateFunctionParams {
+  final String functionName;
+  final ScalarFunction function;
+  final AllowedArgumentCount argumentCount;
+  final bool deterministic;
+  final bool directOnly;
+
+  const _CreateFunctionParams({
+    required this.functionName,
+    required this.function,
+    this.argumentCount = const AllowedArgumentCount.any(),
+    this.deterministic = false,
+    this.directOnly = true,
+  });
+}

pubspec.yaml

@@ -12,10 +12,10 @@ dependencies:
     sdk: flutter
   logging: ^1.2.0
   logging_appenders: ^1.3.1
-  sqlite3: ^2.4.4
+  sqlite3: ^2.4.7
 
 dev_dependencies:
   flutter_test:
     sdk: flutter
   flutter_lints: ^4.0.0
-  sqlite3_flutter_libs: ^0.5.24
+  sqlite3_flutter_libs: ^0.5.26

test/sqlite3_async_test.dart

@@ -82,6 +82,32 @@ void main() {
     expect(fullInsertionsTime, greaterThan(triggeredInsertionsTime));
     await db.dispose();
   });
+
+  test('create custom function', () async {
+    var db = await AsyncDatabase.open(testDbPath);
+    await _createTable(db);
+
+    await db.createFunction(
+      functionName: 'get_int_from_row_name',
+      argumentCount: const AllowedArgumentCount(1),
+      function: (args) {
+        final [name as String] = args;
+        return int.parse(name.split('_')[1]);
+      },
+    );
+
+    for (int i = 0; i < 100; i++) {
+      await _insertItem("a_$i", db);
+    }
+
+    var rows = await db.select(
+        "SELECT name, get_int_from_row_name(name) as name_int FROM items");
+
+    expect(
+        rows.every((element) => element['name'] == 'a_${element['name_int']}'),
+        true);
+    await db.dispose();
+  });
 }
 
 Future<void> _insertItem(String itemName, AsyncDatabase db) {