Exclude wrapped properties from assign-only analysis (#1004)

Author: ileitch

CHANGELOG.md

@@ -6,7 +6,7 @@
 
 ##### Enhancements
 
-- None.
+- Exclude wrapped properties from assign-only analysis, as Periphery cannot observe the behavior of the property wrapper.
 
 ##### Bug Fixes
 

Sources/SourceGraph/Mutators/AssignOnlyPropertyReferenceEliminator.swift

@@ -7,7 +7,6 @@ final class AssignOnlyPropertyReferenceEliminator: SourceGraphMutator {
     private let configuration: Configuration
     private let retainAssignOnlyPropertyTypes: [String]
     private let defaultRetainedTypes = ["AnyCancellable", "Set<AnyCancellable>", "[AnyCancellable]", "NSKeyValueObservation"]
-    private let retainedAttributes = ["State", "Binding"]
 
     required init(graph: SourceGraph, configuration: Configuration, swiftVersion _: SwiftVersion) {
         self.graph = graph
@@ -24,7 +23,7 @@ final class AssignOnlyPropertyReferenceEliminator: SourceGraphMutator {
             guard let declaredType = property.declaredType,
                   !retainAssignOnlyPropertyTypes.contains(declaredType),
                   !graph.isRetained(property),
-                  property.attributes.isDisjoint(with: retainedAttributes),
+                  property.attributes.isEmpty,
                   !property.isComplexProperty,
                   // A protocol property can technically be assigned and never used when the protocol is used as an existential
                   // type, however communicating that succinctly would be very tricky, and most likely just lead to confusion.

Tests/Fixtures/Sources/RetentionFixtures/testSimplePropertyAssignedButNeverRead.swift

@@ -25,6 +25,9 @@ public class FixtureClass70 {
     // periphery:ignore
     var ignoredSimpleUnreadVar: String
 
+    @Wrapped
+    var wrappedProperty: String
+
     init() {
         simpleUnreadVar = "Hello"
         simpleUnreadShadowedVar = "Hello"
@@ -33,6 +36,7 @@ public class FixtureClass70 {
         complexUnreadVar1 = "Hello"
         readVar = "Hello"
         ignoredSimpleUnreadVar = "Hello"
+        wrappedProperty = "Hello"
         FixtureClass70.simpleStaticUnreadVar = "Hello"
     }
 
@@ -44,3 +48,11 @@ public class FixtureClass70 {
         print(readVar)
     }
 }
+
+@propertyWrapper
+struct Wrapped<Value> {
+    var wrappedValue: Value
+    init(wrappedValue: Value) {
+        self.wrappedValue = wrappedValue
+    }
+}

Tests/PeripheryTests/RetentionTest.swift

@@ -1220,6 +1220,9 @@ final class RetentionTest: FixtureSourceGraphTestCase {
 
                 self.assertReferenced(.varInstance("ignoredSimpleUnreadVar"))
                 self.assertNotAssignOnlyProperty(.varInstance("ignoredSimpleUnreadVar"))
+
+                self.assertReferenced(.varInstance("wrappedProperty"))
+                self.assertNotAssignOnlyProperty(.varInstance("wrappedProperty"))
             }
         }
 
@@ -1248,6 +1251,9 @@ final class RetentionTest: FixtureSourceGraphTestCase {
 
                 self.assertReferenced(.varInstance("ignoredSimpleUnreadVar"))
                 self.assertNotAssignOnlyProperty(.varInstance("ignoredSimpleUnreadVar"))
+
+                self.assertReferenced(.varInstance("wrappedProperty"))
+                self.assertNotAssignOnlyProperty(.varInstance("wrappedProperty"))
             }
         }
     }