feat: improve avoid-returning-widgets builder functions handling (#693)

Co-authored-by: Dmitry Krutskikh <dmitry.krutskikh@gmail.com>

Author: incendial

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 * chore: activate new lint rules.
+* feat: improve `avoid-returning-widgets` builder functions handling.
 * fix: correctly handle const maps in `no-magic-number`.
 
 ## 4.11.0-dev.1

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_returning_widgets/avoid_returning_widgets_rule.dart

@@ -3,6 +3,7 @@
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/dart/element/type.dart';
 
 import '../../../../../utils/flutter_types_utils.dart';
 import '../../../../../utils/node_utils.dart';

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_returning_widgets/visitor.dart

@@ -72,10 +72,25 @@ class _InvocationsVisitor extends RecursiveAstVisitor<void> {
   @override
   void visitMethodInvocation(MethodInvocation node) {
     if (_declarationNames.contains(node.methodName.name) &&
-        node.realTarget == null) {
+        node.realTarget == null &&
+        !_isInsideBuilder(node)) {
       _invocations.add(node);
     }
   }
+
+  bool _isInsideBuilder(MethodInvocation node) {
+    final expression = node.thisOrAncestorOfType<NamedExpression>();
+
+    if (expression is NamedExpression) {
+      final type = expression.staticType;
+      if (type is FunctionType) {
+        return type.returnType is InterfaceType &&
+            hasWidgetType(type.returnType);
+      }
+    }
+
+    return false;
+  }
 }
 
 class _DeclarationsVisitor extends RecursiveAstVisitor<void> {

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_returning_widgets/examples/example.dart

@@ -93,3 +93,29 @@ class Builder extends Widget {
 }
 
 class StatelessWidget extends Widget {}
+
+class MyOtherWidget extends StatelessWidget {
+  Widget _buildMyWidget(BuildContext context) {
+    return Container();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Builder(builder: (context) {
+      return _buildMyWidget(context);
+    });
+  }
+}
+
+class MyAnotherWidget extends StatelessWidget {
+  Widget _buildMyWidget(BuildContext context) {
+    return Container();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Builder(
+      builder: (context) => _buildMyWidget(context),
+    );
+  }
+}