Add '--retain-codable-properties' option

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Add experimental unused import analysis.
 - The option `--external-encodable-protocols` is deprecated, use `--external-codable-protocols` instead.
 - Assign-only properties on structs with synthesized initializers are now detected.
+- Added the `--retain-codable-properties` option to retain all properties on Codable types.
 
 ##### Bug Fixes
 

Sources/Frontend/Commands/ScanCommand.swift

@@ -84,6 +84,9 @@ struct ScanCommand: FrontendCommand {
     @Flag(help: "Retain SwiftUI previews")
     var retainSwiftUIPreviews: Bool = defaultConfiguration.$retainSwiftUIPreviews.defaultValue
 
+    @Flag(help: "Retain properties on Codable types")
+    var retainCodableProperties: Bool = defaultConfiguration.$retainCodableProperties.defaultValue
+
     @Flag(help: "Clean existing build artifacts before building")
     var cleanBuild: Bool = defaultConfiguration.$cleanBuild.defaultValue
 
@@ -150,6 +153,7 @@ struct ScanCommand: FrontendCommand {
         configuration.apply(\.$cleanBuild, cleanBuild)
         configuration.apply(\.$buildArguments, buildArguments)
         configuration.apply(\.$relativeResults, relativeResults)
+        configuration.apply(\.$retainCodableProperties, retainCodableProperties)
 
         try scanBehavior.main { project in
             try Scan().perform(project: project)

Sources/PeripheryKit/SourceGraph/Mutators/CodablePropertyRetainer.swift

@@ -0,0 +1,25 @@
+import Foundation
+import Shared
+
+final class CodablePropertyRetainer: SourceGraphMutator {
+    private let graph: SourceGraph
+    private let configuration: Configuration
+
+    required init(graph: SourceGraph, configuration: Configuration) {
+        self.graph = graph
+        self.configuration = configuration
+    }
+
+    func mutate() {
+        guard configuration.retainCodableProperties else { return }
+
+        for decl in graph.declarations(ofKinds: Declaration.Kind.discreteConformableKinds) {
+            guard graph.isCodable(decl) else { continue }
+
+            for decl in decl.declarations {
+                guard decl.kind == .varInstance else { continue }
+                graph.markRetained(decl)
+            }
+        }
+    }
+}

Sources/PeripheryKit/SourceGraph/SourceGraphMutatorRunner.swift

@@ -43,6 +43,7 @@ public final class SourceGraphMutatorRunner {
         PropertyWrapperRetainer.self,
         ResultBuilderRetainer.self,
         CapitalSelfFunctionCallRetainer.self,
+        CodablePropertyRetainer.self,
 
         AncestralReferenceEliminator.self,
         AssignOnlyPropertyReferenceEliminator.self,

Sources/Shared/Configuration.swift

@@ -77,6 +77,9 @@ public final class Configuration {
     @Setting(key: "enable_unused_import_analysis", defaultValue: false)
     public var enableUnusedImportsAnalysis: Bool
 
+    @Setting(key: "retain_codable_properties", defaultValue: false)
+    public var retainCodableProperties: Bool
+
     @Setting(key: "verbose", defaultValue: false)
     public var verbose: Bool
 
@@ -230,6 +233,10 @@ public final class Configuration {
             config[$relativeResults.key] = relativeResults
         }
 
+        if $retainCodableProperties.hasNonDefaultValue {
+            config[$retainCodableProperties.key] = retainCodableProperties
+        }
+
         return try Yams.dump(object: config)
     }
 
@@ -309,6 +316,8 @@ public final class Configuration {
                 $buildArguments.assign(value)
             case $relativeResults.key:
                 $relativeResults.assign(value)
+            case $retainCodableProperties.key:
+                $retainCodableProperties.assign(value)
             default:
                 logger.warn("\(path.string): invalid key '\(key)'")
             }
@@ -346,6 +355,7 @@ public final class Configuration {
         $cleanBuild.reset()
         $buildArguments.reset()
         $relativeResults.reset()
+        $retainCodableProperties.reset()
     }
 
     // MARK: - Helpers

Tests/Fixtures/RetentionFixtures/testRetainsCodableProperties.swift

@@ -0,0 +1,9 @@
+import Foundation
+
+public struct FixtureStruct14: Codable {
+    let unused: Int
+
+    init(unused: Int) {
+        self.unused = unused
+    }
+}

Tests/PeripheryTests/RetentionTest.swift

@@ -999,6 +999,28 @@ final class RetentionTest: FixtureSourceGraphTestCase {
         }
     }
 
+    func testRetainsCodableProperties() {
+        configuration.retainCodableProperties = false
+        configuration.retainAssignOnlyProperties = false
+
+        analyze(retainPublic: true) {
+            assertReferenced(.struct("FixtureStruct14")) {
+                self.assertNotReferenced(.functionConstructor("init(unused:)"))
+                self.assertAssignOnlyProperty(.varInstance("unused"))
+            }
+        }
+
+        configuration.retainCodableProperties = true
+
+        analyze(retainPublic: true) {
+            assertReferenced(.struct("FixtureStruct14")) {
+                self.assertNotReferenced(.functionConstructor("init(unused:)"))
+                self.assertReferenced(.varInstance("unused"))
+                self.assertNotAssignOnlyProperty(.varInstance("unused"))
+            }
+        }
+    }
+
     // MARK: - Assign-only properties
 
     func testStructImplicitInitializer() {