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Issue #148: work in progress (do not merge), new rule avoid_initstate_field_initialization
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‎lib/analysis_options.yaml‎

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@@ -43,6 +43,7 @@ custom_lint:
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ignored_types:
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- AnimationController
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- avoid_initstate_field_initialization
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- avoid_non_null_assertion
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- avoid_returning_widgets
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- avoid_unnecessary_return_variable

‎lib/solid_lints.dart‎

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@@ -4,6 +4,7 @@ import 'package:custom_lint_builder/custom_lint_builder.dart';
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import 'package:solid_lints/src/lints/avoid_debug_print_in_release/avoid_debug_print_in_release_rule.dart';
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import 'package:solid_lints/src/lints/avoid_final_with_getter/avoid_final_with_getter_rule.dart';
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import 'package:solid_lints/src/lints/avoid_global_state/avoid_global_state_rule.dart';
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import 'package:solid_lints/src/lints/avoid_initstate_field_initialization/avoid_initstate_field_initialization_rule.dart';
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import 'package:solid_lints/src/lints/avoid_late_keyword/avoid_late_keyword_rule.dart';
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import 'package:solid_lints/src/lints/avoid_non_null_assertion/avoid_non_null_assertion_rule.dart';
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import 'package:solid_lints/src/lints/avoid_returning_widgets/avoid_returning_widgets_rule.dart';
@@ -69,6 +70,7 @@ class _SolidLints extends PluginBase {
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AvoidFinalWithGetterRule.createRule(configs),
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NamedParametersOrderingRule.createRule(configs),
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AvoidUnnecessaryReturnVariableRule.createRule(configs),
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AvoidInitstateFieldInitializationRule.createRule(configs),
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];
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// Return only enabled rules

‎lib/src/lints/avoid_initstate_field_initialization/avoid_initstate_field_initialization_rule.dart‎

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@@ -0,0 +1,173 @@
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import 'package:analyzer/dart/ast/ast.dart';
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import 'package:analyzer/dart/ast/visitor.dart';
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import 'package:analyzer/error/listener.dart';
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import 'package:collection/collection.dart';
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import 'package:custom_lint_builder/custom_lint_builder.dart';
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import 'package:solid_lints/src/lints/avoid_initstate_field_initialization/visitors/avoid_initstate_field_initialization_visitor.dart';
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import 'package:solid_lints/src/models/rule_config.dart';
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import 'package:solid_lints/src/models/solid_lint_rule.dart';
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/// An `avoid_initstate_field_initialization` rule which suggests using
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/// declaration initializer over initializing field from `initState()`
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/// if possible.
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///
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/// See more here: https://github.com/solid-software/solid_lints/issues/148
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///
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/// ### Example
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///
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/// #### BAD:
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///
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/// ```dart
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/// class SomeState extends State<Some> {
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/// late final X? x;
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/// void initState() {
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/// x = widget.x;
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/// }
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/// }
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/// ```
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///
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/// #### GOOD:
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///
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/// ```dart
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/// class SomeState extends State<Some> {
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/// late final x = widget.x;
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/// }
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/// ```
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///
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class AvoidInitstateFieldInitializationRule extends SolidLintRule {
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/// This lint rule represents the error when field
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/// is initialized from `initState()`
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/// when declaration initializer is possible.
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static const lintName = 'avoid_initstate_field_initialization';
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/// Name of `initState()` method.
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static const initState = 'initState';
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AvoidInitstateFieldInitializationRule._(super.config);
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/// Creates a new instance of [AvoidInitstateFieldInitializationRule]
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/// based on the lint configuration.
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factory AvoidInitstateFieldInitializationRule.createRule(
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CustomLintConfigs configs,
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) {
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final rule = RuleConfig(
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configs: configs,
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name: lintName,
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problemMessage: (_) => """
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Avoid initialization final fields in initState().
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Use declaration initializer instead.""",
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);
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return AvoidInitstateFieldInitializationRule._(rule);
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}
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@override
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void run(
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CustomLintResolver resolver,
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ErrorReporter reporter,
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CustomLintContext context,
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) {
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context.registry.addClassDeclaration((classDec) {
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_checkClass(
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classDec: classDec,
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reporter: reporter,
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context: context,
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);
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});
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// context.registry.addMethodDeclaration(
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// (method) {
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// if (method.name.toString() != initState) return;
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// _checkInitStateMethod(
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// method: method,
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// reporter: reporter,
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// context: context,
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// );
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// },
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// );
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}
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void _checkClass({
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required ClassDeclaration classDec,
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required ErrorReporter reporter,
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required CustomLintContext context,
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}) {
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final classElement = classDec.declaredFragment?.element;
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if (classElement == null) return;
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//shortcut by checking class info without any visitor
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final initStateMethod = classElement.methods2.firstWhereOrNull(
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(method) => method.name3 == initState,
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);
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if (initStateMethod == null) return;
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//TODO REMOVE THIS
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//For test purposes ignoring all classes except in test file.
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if (!classElement.name3.toString().startsWith("_TestWidgetState")) return;
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print("\n${classElement.name3}");
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//TODO END REMOVE
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final visitor = AvoidInitstateFieldInitializationVisitor();
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classDec.accept(visitor);
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}
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void _checkInitStateMethod({
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required MethodDeclaration method,
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required ErrorReporter reporter,
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required CustomLintContext context,
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}) {
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final classDeclaration = method.thisOrAncestorOfType<ClassDeclaration>();
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final classElement = classDeclaration?.declaredFragment?.element;
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if (classElement == null) return;
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//TODO REMOVE THIS
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//For test purposes ignoring all classes except in test file.
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if (!classElement.name3.toString().startsWith("_TestWidgetState")) return;
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print("\n${classElement.name3}");
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//TODO END REMOVE
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//fields are clearly recognizeable here
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print(classElement.fields2);
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AstNode body = method.body;
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while (body.childEntities.firstOrNull != null) {
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if (body.childEntities.first is! AstNode) break;
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body = body.childEntities.first as AstNode;
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}
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for (final child in body.childEntities) {
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// print(child);
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// print(child.runtimeType);
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if (child is! ExpressionStatement) continue;
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final expr = child.expression;
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if (expr is! AssignmentExpression) continue;
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final leftHand = expr.leftHandSide;
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if (leftHand is! SimpleIdentifier) continue;
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print(leftHand.element);
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if (child.expression case final SimpleIdentifier id) {
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print(id.element);
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}
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}
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//TODO: if restoring this method, visitor should become Recursive again
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final visitor = AvoidInitstateFieldInitializationVisitor();
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method.visitChildren(visitor);
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}
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}
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//HACK: Failed attempt to use separate visitor, didn't help
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class _VisitorWrapper extends SimpleAstVisitor<void> {
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@override
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void visitMethodDeclaration(MethodDeclaration node) {
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if (node.name.toString() !=
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AvoidInitstateFieldInitializationRule.initState) {
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return;
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}
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final visitor = AvoidInitstateFieldInitializationVisitor();
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node.visitChildren(visitor);
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}
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}

‎lib/src/lints/avoid_initstate_field_initialization/visitors/avoid_initstate_field_initialization_visitor.dart‎

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import 'package:analyzer/dart/ast/ast.dart';
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import 'package:analyzer/dart/ast/visitor.dart';
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import 'package:solid_lints/src/lints/avoid_initstate_field_initialization/avoid_initstate_field_initialization_rule.dart';
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// import 'package:analyzer/dart/element/element2.dart';
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// import 'package:collection/collection.dart';
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/// TODO DESCRIPTION
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class AvoidInitstateFieldInitializationVisitor extends SimpleAstVisitor<void> {
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@override
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void visitClassDeclaration(ClassDeclaration node) {
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super.visitClassDeclaration(node);
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node.visitChildren(this);
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}
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@override
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void visitMethodDeclaration(MethodDeclaration node) {
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super.visitMethodDeclaration(node);
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if (node.name.toString() !=
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AvoidInitstateFieldInitializationRule.initState) {
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return;
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}
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AstNode body = node.body;
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while (body.childEntities.firstOrNull != null) {
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if (body.childEntities.first is! AstNode) break;
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body = body.childEntities.first as AstNode;
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}
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body.visitChildren(this);
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}
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@override
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void visitExpressionStatement(ExpressionStatement node) {
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super.visitExpressionStatement(node);
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node.visitChildren(this);
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}
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@override
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void visitAssignmentExpression(AssignmentExpression node) {
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super.visitAssignmentExpression(node);
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if (node.leftHandSide case final SimpleIdentifier field
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//when field.element is FieldElement2
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) {
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_processVisitedVariable(node, field);
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}
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}
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void _processVisitedVariable(
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AssignmentExpression node,
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SimpleIdentifier identifier,
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) {
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//TODO: why identifier.element is this null?
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print("$node ; $identifier ; ${identifier.element}");
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}
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}

‎lint_test/analysis_options.yaml‎

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@@ -90,3 +90,4 @@ custom_lint:
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- nullable
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- default
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- avoid_unnecessary_return_variable
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- avoid_initstate_field_initialization

‎lint_test/avoid_initstate_field_initialization_test.dart‎

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// ignore_for_file: unused_local_variable, prefer_match_file_name, avoid_late_keyword, member_ordering
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import 'package:flutter/widgets.dart';
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/// Widget to test avoid_initstate_field_initialization rule.
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class TestWidget extends StatefulWidget {
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static const int xConst = 0;
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//ignore: avoid_global_state
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static int xStaticVariable = 0;
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final int xFinal = 0;
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@override
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State<TestWidget> createState() => _TestWidgetStateBad();
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}
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class _TestWidgetStateBad extends State<TestWidget> {
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late final int? a;
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late final int? b;
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void initState() {
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super.initState();
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//expect_lint: avoid_initstate_field_initialization
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a = widget.xFinal;
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//expect_lint: avoid_initstate_field_initialization
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b = (widget.xFinal + TestWidget.xConst) * 1;
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}
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@override
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Widget build(BuildContext context) {
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throw UnimplementedError();
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}
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}
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// ignore: unused_element
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class _TestWidgetStateGood extends State<TestWidget> {
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late final a = widget.xFinal;
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late final int? b;
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late final int? c;
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late final int? d;
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late final int? e;
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late final int? f;
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late final g = widget.xFinal + TestWidget.xConst;
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late final int? h;
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int? k;
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void initState() {
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super.initState();
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//init from local variable
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final bLocal = 1;
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b = bLocal;
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//init from external mutable
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c = TestWidget.xStaticVariable;
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//init from method result
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d = _evaluateSomething();
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//init from expression with variable
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e = widget.xFinal + TestWidget.xStaticVariable;
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//init more than once by arbitrary logic
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f = widget.xFinal;
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if (widget.xFinal <= 0) {
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f = TestWidget.xConst;
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}
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//init conditionally (possible null value)
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if (bLocal <= TestWidget.xConst) {
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h = widget.xFinal;
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}
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//init variable, not final
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k = widget.xFinal;
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//init local variable
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int localInit;
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localInit = 0;
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}
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@override
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Widget build(BuildContext context) {
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throw UnimplementedError();
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}
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int _evaluateSomething() => 1;
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}

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