fix: partially handle normal completion function body for avoid-redundant-async (#1148)

* fix: partially handle normal completion function body for avoid-redundant-async

* fix: count all returns inside function

Author: incendial

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* fix: partially handle normal completion function body for [`avoid-redundant-async`](https://dcm.dev/docs/individuals/rules/common/avoid-redundant-async).
 * fix: ignore enum constant arguments for [`no-magic-number`](https://dcm.dev/docs/individuals/rules/common/no-magic-number).
 * fix: correctly handle prefixed enums and static instance fields for [`prefer-moving-to-variable`](https://dcm.dev/docs/individuals/rules/common/prefer-moving-to-variable).
 * feat: add static code diagnostic [`prefer-provide-intl-description`](https://dcm.dev/docs/individuals/rules/intl/prefer-provide-intl-description).

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

@@ -37,22 +37,40 @@ class _Visitor extends RecursiveAstVisitor<void> {
       }
     }
 
-    final asyncVisitor = _AsyncVisitor();
+    final asyncVisitor = _AsyncVisitor(body);
     body.parent?.visitChildren(asyncVisitor);
 
+    if (asyncVisitor._allReturns.isNotEmpty) {
+      return !asyncVisitor.hasValidAsync &&
+          asyncVisitor._allReturns.length !=
+              asyncVisitor._returnsInsideIf.length;
+    }
+
     return !asyncVisitor.hasValidAsync;
   }
 }
 
 class _AsyncVisitor extends RecursiveAstVisitor<void> {
+  final FunctionBody body;
+
   bool hasValidAsync = false;
 
+  final _allReturns = <ReturnStatement>{};
+  final _returnsInsideIf = <ReturnStatement>{};
+
+  _AsyncVisitor(this.body);
+
   @override
   void visitReturnStatement(ReturnStatement node) {
     super.visitReturnStatement(node);
 
     final type = node.expression?.staticType;
 
+    _allReturns.add(node);
+    if (_isInsideIfStatement(node, body)) {
+      _returnsInsideIf.add(node);
+    }
+
     if (type == null ||
         !type.isDartAsyncFuture ||
         type.nullabilitySuffix == NullabilitySuffix.question) {
@@ -80,4 +98,12 @@ class _AsyncVisitor extends RecursiveAstVisitor<void> {
 
     hasValidAsync = true;
   }
+
+  bool _isInsideIfStatement(ReturnStatement node, FunctionBody body) {
+    final parent = node.thisOrAncestorMatching(
+      (parent) => parent == body || parent is IfStatement,
+    );
+
+    return parent is IfStatement;
+  }
 }

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

@@ -59,4 +59,12 @@ void main() {
     () async => instance.someAsyncMethod(), // LINT
     onSelectedNamed: () async => instance.someAsyncMethod(), // LINT
   );
+
+  WithFunctionField(onSelectedNamed: () async {
+    if (shouldRefresh) return apiCall();
+  });
+}
+
+Future<void> apiCall() {
+  return Future.value();
 }