Ignore override declarations in async_without_await rule (#6417)

Co-authored-by: Danny Mösch <danny.moesch@icloud.com>

CHANGELOG.md

@@ -16,6 +16,10 @@
 
 ### Bug Fixes
 
+* Ignore `override` functions in `async_without_await` rule.  
+  [SimplyDanny](https://github.com/SimplyDanny)
+  [#6416](https://github.com/realm/SwiftLint/issues/6416)
+
 * Fix false positive in `unneeded_escaping` rule when an escaping closure is used in
   a nested closure preceded by another closure.  
   [SimplyDanny](https://github.com/SimplyDanny)

Source/SwiftLintBuiltInRules/Rules/Lint/AsyncWithoutAwaitRule.swift

@@ -26,15 +26,10 @@ private extension AsyncWithoutAwaitRule {
         private var pendingAsync: TokenSyntax?
 
         override func visit(_ node: FunctionDeclSyntax) -> SyntaxVisitorContinueKind {
-            guard node.body != nil else {
-                return .visitChildren
+            if node.body != nil {
+                let asyncToken = node.needsToKeepAsync ? nil : node.signature.effectSpecifiers?.asyncSpecifier
+                functionScopes.push(.init(asyncToken: asyncToken))
             }
-
-            // @concurrent functions require the async keyword even without await calls
-            let asyncToken = node.attributes.contains(attributeNamed: "concurrent")
-                ? nil : node.signature.effectSpecifiers?.asyncSpecifier
-            functionScopes.push(.init(asyncToken: asyncToken))
-
             return .visitChildren
         }
 
@@ -45,7 +40,7 @@ private extension AsyncWithoutAwaitRule {
         }
 
         override func visit(_ node: ClosureExprSyntax) -> SyntaxVisitorContinueKind {
-            // @concurrent closures require the async keyword even without await calls
+            // @concurrent closures require the async keyword even without await calls,
             let asyncToken = (node.signature?.attributes.contains(attributeNamed: "concurrent") ?? false)
                 ? nil : pendingAsync
             functionScopes.push(.init(asyncToken: asyncToken))
@@ -62,13 +57,10 @@ private extension AsyncWithoutAwaitRule {
         }
 
         override func visit(_ node: AccessorDeclSyntax) -> SyntaxVisitorContinueKind {
-            guard node.body != nil else {
-                return .visitChildren
+            if node.body != nil {
+                let asyncToken = node.needsToKeepAsync ? nil : node.effectSpecifiers?.asyncSpecifier
+                functionScopes.push(.init(asyncToken: asyncToken))
             }
-
-            let asyncToken = node.effectSpecifiers?.asyncSpecifier
-            functionScopes.push(.init(asyncToken: asyncToken))
-
             return .visitChildren
         }
 
@@ -79,15 +71,10 @@ private extension AsyncWithoutAwaitRule {
         }
 
         override func visit(_ node: InitializerDeclSyntax) -> SyntaxVisitorContinueKind {
-            guard node.body != nil else {
-                return .visitChildren
+            if node.body != nil {
+                let asyncToken = node.needsToKeepAsync ? nil : node.signature.effectSpecifiers?.asyncSpecifier
+                functionScopes.push(.init(asyncToken: asyncToken))
             }
-
-            // @concurrent can be applied to initializers
-            let asyncToken = node.attributes.contains(attributeNamed: "concurrent")
-                ? nil : node.signature.effectSpecifiers?.asyncSpecifier
-            functionScopes.push(.init(asyncToken: asyncToken))
-
             return .visitChildren
         }
 
@@ -163,3 +150,21 @@ private extension TypeSyntax {
         return nil
     }
 }
+
+private extension WithModifiersSyntax where Self: WithAttributesSyntax {
+    var needsToKeepAsync: Bool {
+        attributes.contains(attributeNamed: "concurrent") || modifiers.contains(keyword: .override)
+    }
+}
+
+private extension SyntaxProtocol {
+    var needsToKeepAsync: Bool {
+        if let variableDecl = `as`(VariableDeclSyntax.self) {
+            return variableDecl.needsToKeepAsync
+        }
+        if let subscriptDecl = `as`(SubscriptDeclSyntax.self) {
+            return subscriptDecl.needsToKeepAsync
+        }
+        return parent?.needsToKeepAsync ?? false
+    }
+}

Source/SwiftLintBuiltInRules/Rules/Lint/AsyncWithoutAwaitRuleExamples.swift

@@ -188,6 +188,34 @@ internal struct AsyncWithoutAwaitRuleExamples {
             let c: () async -> Int = { @concurrent in 1 }
         }
         """),
+        Example("""
+        class Parent {
+            func test() async { await foo() }
+        }
+        class Child: Parent {
+            override func test() async { print("Child") }
+        }
+        """),
+        Example("""
+        class Parent {
+            var prop: Int {
+                get async { await fetchValue() }
+            }
+        }
+        class Child: Parent {
+            override var prop: Int {
+                get async { return 2 }
+            }
+        }
+        """),
+        Example("""
+        class Base {
+            init() async { await setup() }
+        }
+        class Derived: Base {
+            override init() async { print("Derived") }
+        }
+        """),
     ]
 
     static let triggeringExamples = [