moor_ffi: Assert right parameter count (#608)

moor_ffi/lib/src/bindings/bindings.dart

@@ -90,6 +90,7 @@ class _SQLiteBindings {
       int length,
       Pointer<Void> disposeCb) sqlite3_bind_blob;
   int Function(Pointer<Statement> statement, int columnIndex) sqlite3_bind_null;
+  sqlite3_bind_parameter_count_dart sqlite3_bind_parameter_count;
 
   int Function(
     Pointer<Database> db,
@@ -136,6 +137,9 @@ class _SQLiteBindings {
     sqlite3_bind_null = sqlite
         .lookup<NativeFunction<sqlite3_bind_null_native>>('sqlite3_bind_null')
         .asFunction();
+    sqlite3_bind_parameter_count = sqlite.lookupFunction<
+        sqlite3_bind_parameter_count_native,
+        sqlite3_bind_parameter_count_dart>('sqlite3_bind_parameter_count');
     sqlite3_open_v2 = sqlite
         .lookup<NativeFunction<sqlite3_open_v2_native_t>>('sqlite3_open_v2')
         .asFunction();

moor_ffi/lib/src/bindings/signatures.dart

@@ -93,6 +93,10 @@ typedef sqlite3_bind_blob_native = Int32 Function(
     Pointer<Void> callback);
 typedef sqlite3_bind_null_native = Int32 Function(
     Pointer<Statement> statement, Int32 columnIndex);
+typedef sqlite3_bind_parameter_count_dart = int Function(
+    Pointer<Statement> stmt);
+typedef sqlite3_bind_parameter_count_native = Int32 Function(
+    Pointer<Statement> statement);
 
 typedef sqlite3_function_handler = Void Function(
     Pointer<FunctionContext> context,

moor_ffi/lib/src/impl/prepared_statement.dart

@@ -21,6 +21,12 @@ class PreparedStatement {
     _closed = true;
   }
 
+  /// Returns the amount of parameters in this prepared statement.
+  ///
+  /// See also:
+  /// - `sqlite3_bind_parameter_count`: https://www.sqlite.org/c3ref/bind_parameter_count.html
+  int get parameterCount => bindings.sqlite3_bind_parameter_count(_stmt);
+
   void _ensureNotFinalized() {
     if (_closed) {
       throw StateError('Tried to operate on a released prepared statement');
@@ -30,6 +36,11 @@ class PreparedStatement {
   /// Executes this prepared statement as a select statement. The returned rows
   /// will be returned.
   Result select([List<dynamic> params]) {
+    assert(
+      (params?.length ?? 0) == parameterCount,
+      'Expected $parameterCount params, but got ${params?.length ?? 0}.',
+    );
+
     _ensureNotFinalized();
     _reset();
     _bindParams(params);

moor_ffi/test/database/prepared_statements_test.dart

@@ -118,6 +118,22 @@ void main() {
     expect(() => stmt.execute([false]), throwsArgumentError);
     db.close();
   });
+
+  group('asserts that the amount of parameters are correct', () {
+    final db = Database.memory();
+
+    test('when no parameters are set', () {
+      final stmt = db.prepare('SELECT ?');
+      expect(stmt.select, throwsA(isA<AssertionError>()));
+    });
+
+    test('when the wrong amount of parameters are set', () {
+      final stmt = db.prepare('SELECT ?, ?');
+      expect(() => stmt.select([1]), throwsA(isA<AssertionError>()));
+    });
+
+    tearDownAll(db.close);
+  });
 }
 
 void _raiseIfTwo(Pointer<FunctionContext> ctx, int argCount,