| // Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| import 'package:analyzer/dart/ast/ast.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| |
| import '../analyzer.dart'; |
| import '../util/flutter_utils.dart'; |
| |
| const _desc = r"Don't put any logic in createState."; |
| |
| const _details = r''' |
| **DON'T** put any logic in `createState()`. |
| |
| Implementations of `createState()` should return a new instance |
| of a State object and do nothing more. Since state access is preferred |
| via the `widget` field, passing data to `State` objects using custom |
| constructor parameters should also be avoided and so further, the State |
| constructor is required to be passed no arguments. |
| |
| **BAD:** |
| ``` |
| MyState global; |
| |
| class MyStateful extends StatefulWidget { |
| @override |
| MyState createState() { |
| global = MyState(); |
| return global; |
| } |
| } |
| ``` |
| |
| ``` |
| class MyStateful extends StatefulWidget { |
| @override |
| MyState createState() => MyState()..field = 42; |
| } |
| ``` |
| |
| ``` |
| class MyStateful extends StatefulWidget { |
| @override |
| MyState createState() => MyState(42); |
| } |
| ``` |
| |
| |
| **GOOD:** |
| ``` |
| class MyStateful extends StatefulWidget { |
| @override |
| MyState createState() { |
| return MyState(); |
| } |
| } |
| ``` |
| '''; |
| |
| class NoLogicInCreateState extends LintRule implements NodeLintRule { |
| NoLogicInCreateState() |
| : super( |
| name: 'no_logic_in_create_state', |
| description: _desc, |
| details: _details, |
| group: Group.errors); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this); |
| registry.addMethodDeclaration(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitMethodDeclaration(MethodDeclaration node) { |
| if (node.name.name != 'createState') { |
| return; |
| } |
| |
| final parent = node.parent; |
| if (parent is! ClassDeclaration || |
| !isStatefulWidget((parent as ClassDeclaration).declaredElement)) { |
| return; |
| } |
| final body = node.body; |
| Expression expressionToTest; |
| if (body is BlockFunctionBody) { |
| final statements = body.block.statements; |
| if (statements.length == 1) { |
| final statement = statements[0]; |
| if (statement is ReturnStatement) { |
| expressionToTest = statement.expression; |
| } |
| } |
| } else if (body is ExpressionFunctionBody) { |
| expressionToTest = body.expression; |
| } |
| |
| if (expressionToTest is InstanceCreationExpression) { |
| if (expressionToTest.argumentList.arguments.isEmpty) { |
| return; |
| } |
| } |
| rule.reportLint(expressionToTest ?? body); |
| } |
| } |