自作で Dart の Custom Lint パッケージを公開した話

setState() called after dispose(): This error happens if you call setState() on a State object for a widget that no longer appears in the widget tree (e.g., whose dispose() method has been called).

lib/use_setstate_synchronously_rule.dart:30:5 • Avoid calling setState across asynchronous gaps without seeing if the widget is mounted. • use_setstate_synchronously • WARNING

$ fvm dart add analyzer analyzer_plugin custom_lint_builder

➜  sangria git:(develop) tree
.
├── CHANGELOG.md
├── LICENSE
├── README.md
├── analysis_options.yaml
├── example
│   ├── analysis_options.yaml
│   ├── lib
│   │   └── use_setstate_synchronously_rule.dart
│   ├── main.dart
│   ├── pubspec.lock
│   └── pubspec.yaml
├── lib
│   ├── sangria_lints.dart
│   └── src
│       └── rules
│           └── use_setstate_synchronously
│               ├── use_setstate_synchronously_rule.dart
│               └── use_setstate_synchronously_visitor.dart
├── pubspec.lock
└── pubspec.yaml

8 directories, 20 files

import 'package:custom_lint_builder/custom_lint_builder.dart';
import 'package:sangria_lints/src/rules/use_setstate_synchronously/use_setstate_synchronously_rule.dart';

// Lint ルールのエントリポイント。
PluginBase createPlugin() => _SangriaLints();

class _SangriaLints extends PluginBase {
  static final _lints = [UseSetStateSynchronouslyLintRule()];

  @override
  List<LintRule> getLintRules(CustomLintConfigs configs) {
    return _lints.where((lint) => lint.isEnabled(configs)).toList();
  }
}

class UseSetStateSynchronouslyLintRule extends DartLintRule {
  UseSetStateSynchronouslyLintRule()
    : super(
        code: LintCode(
          name: 'use_setstate_synchronously',
          problemMessage:
              'Avoid calling setState across asynchronous gaps without seeing if the widget is mounted.',
          errorSeverity: ErrorSeverity.WARNING,
        ),
      );

  @override
  void run(
    CustomLintResolver resolver,
    ErrorReporter reporter,
    CustomLintContext context,
  ) {
    // クラスメソッドやインスタンスメソッドの中身を解析・監視するコード
    context.registry.addMethodDeclaration((node) {
      // ...
    });

    // ウィジェットに渡すコールバックの中身を解析・監視するコード
    context.registry.addFunctionExpression((node) {
      //...
    });
  }
}

import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/visitor.dart';
import 'package:analyzer/error/listener.dart';
import 'package:custom_lint_builder/custom_lint_builder.dart';

class UseSetstateSynchronouslyVisitor extends RecursiveAstVisitor<void> {
  UseSetstateSynchronouslyVisitor({
    required this.reporter,
    required this.lintCode,
  });

  final ErrorReporter reporter;
  final LintCode lintCode;

  @override
  void visitIfStatement(node) {
    final expressionStr = node.expression.toString();

    if (expressionStr.contains('!mounted')) {
      // ... !mounted で早期 return している場合警告をあげないなどのロジック
    } else if (expressionStr.contains('mounted')) {
      // ... mounted の条件でラップしている場合警告をあげないなどのロジック
    } else {
      super.visitIfStatement(node);
    }
  }

  @override
  void visitMethodInvocation(MethodInvocation node) {
    // メソッドの名前が setState かつ、早期 return されず、mounted の条件分岐でラップされていない場合、警告をあげる。
    // reporter.atNode(node, lintCode);

    super.visitMethodInvocation(node);
  }
}

$ fvm dart run custom_lint --watch

➜  example git:(develop) ✗ fvm dart run custom_lint --watch
The Dart VM service is listening on http://127.0.0.1:60785/-GnvsQVXzng=/
The Dart DevTools debugger and profiler is available at: http://127.0.0.1:60785/-GnvsQVXzng=/devtools/?uri=ws://127.0.0.1:60785/-GnvsQVXzng=/ws
Analyzing...                           0.0s

No issues found!

Custom lint runner commands:
r: Force re-lint
q: Quit

dev_dependencies:
  sangria_lints:
    path: ../
  custom_lint: 0.7.5

include: package:flutter_lints/flutter.yaml

analyzer:
  plugins:
    - custom_lint

custom_lint:
  debug: true

import 'package:flutter/material.dart';

class UseSetstateSynchronouslyRuleWidget extends StatefulWidget {
  const UseSetstateSynchronouslyRuleWidget({super.key});

  @override
  _UseSetstateSynchronouslyRuleWidgetState createState() =>
      _UseSetstateSynchronouslyRuleWidgetState();
}

class _UseSetstateSynchronouslyRuleWidgetState
    extends State<UseSetstateSynchronouslyRuleWidget> {
  String displayText = '';

  @override
  void initState() {
    super.initState();
  }

  Future<void> setStateAsynchronously() async {
    // expect_lint: use_setstate_synchronously <- これ
    setState(() {
      displayText = 'random string';
    });

    if (!mounted) {
      // expect_lint: use_setstate_synchronously
      setState(() {
        displayText = 'random string'
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        GestureDetector(
          onTap: () async => await setStateAsynchronously(),
          child: Text('addMethodDeclaration'),
        ),
        GestureDetector(
          onTap: () async {
            // expect_lint: use_setstate_synchronously
            setState(() {
              displayText = 'random string'
            });

            if (!mounted) {
              // expect_lint: use_setstate_synchronously
              setState(() {
                displayText = 'random string'
              });
            }
          },
          child: Text('addFunctionExpression'),
        ),
      ],
    );
  }
}

[use_setstate_synchronously] run
[use_setstate_synchronously] run