Set default values ​​for mutable variables via initialization syntax.

Sources/PluginCore/Attributes/CodedBy.swift

@@ -74,7 +74,7 @@ package struct CodedBy: PropertyAttribute {
 extension Registration
 where
     Decl: AttributableDeclSyntax, Var: DefaultPropertyVariable,
-    Var.Initialization == RequiredInitialization
+    Var.Initialization: RequiredVariableInitialization
 {
     /// The optional variable data with helper expression
     /// that output registration will have.

Sources/PluginCore/Attributes/Default.swift

@@ -58,7 +58,7 @@ package struct Default: PropertyAttribute {
 extension Registration
 where
     Decl: AttributableDeclSyntax, Var: PropertyVariable,
-    Var.Initialization == RequiredInitialization
+    Var.Initialization: RequiredVariableInitialization
 {
     /// The variable data with default expression
     /// that output registration will have.
@@ -77,8 +77,31 @@ where
     }
 }
 
+extension AnyPropertyVariable: DefaultPropertyVariable {}
+
+extension Registration
+where
+    Decl: AttributableDeclSyntax, Var: PropertyVariable, 
+    Var.Initialization: RequiredVariableInitialization
+{
+    /// Update registration with binding initializer value. If the ``Default`` attribute is applied, it takes precedence.
+    ///
+    /// New registration is updated with default expression data that will be
+    /// used for decoding failure and memberwise initializer(s), if provided.
+    ///
+    /// - Parameter decl: The declaration to check for attribute.
+    /// - Returns: Newly built registration with default expression data or self.
+    func addDefaultValueIfInitializerExists() -> Registration<Decl, Key, AnyPropertyVariable<AnyRequiredVariableInitialization>> {
+        guard Default(from: decl) == nil, let value = self.variable.value?.trimmed else {
+            return self.updating(with: variable.any)
+        }
+        let newVar = variable.with(default: value)
+        return self.updating(with: newVar.any)
+    }
+}
+
 fileprivate extension PropertyVariable
-where Initialization == RequiredInitialization {
+where Initialization: RequiredVariableInitialization {
     /// Update variable data with the default value expression provided.
     ///
     /// `DefaultValueVariable` is created with this variable as base

Sources/PluginCore/Variables/Initialization/RequiredInitializationWithDefaultValue.swift

@@ -12,7 +12,7 @@ struct RequiredInitializationWithDefaultValue: RequiredVariableInitialization {
     /// syntax is fetched from this value and
     /// updated when adding this initialization
     /// type to init-generator.
-    let base: RequiredInitialization
+    let base: RequiredVariableInitialization
     /// The default expression when
     /// no value provided explicitly.
     ///

Sources/PluginCore/Variables/Initialization/RequiredVariableInitialization.swift

@@ -20,12 +20,3 @@ package protocol RequiredVariableInitialization: VariableInitialization {
     /// generating initializer.
     var code: CodeBlockItemSyntax { get }
 }
-
-extension RequiredVariableInitialization {
-    /// Converts initialization to optional from required initialization.
-    ///
-    /// Wraps current instance in `OptionalInitialization`.
-    var optionalize: OptionalInitialization<Self> {
-        return .init(base: self)
-    }
-}

Sources/PluginCore/Variables/Property/DefaultValueVariable.swift

@@ -10,7 +10,7 @@
 /// * For providing default value to variable in memberwise initializer(s).
 struct DefaultValueVariable<Wrapped>: ComposedVariable, PropertyVariable
 where
-    Wrapped: PropertyVariable, Wrapped.Initialization == RequiredInitialization
+    Wrapped: PropertyVariable, Wrapped.Initialization: RequiredVariableInitialization
 {
     /// The customization options for `DefaultValueVariable`.
     ///

Sources/PluginCore/Variables/Property/InitializationVariable.swift

@@ -110,11 +110,7 @@ where
         in context: some MacroExpansionContext
     ) -> AnyInitialization {
         return if options.`init` {
-            if options.initialized {
-                base.initializing(in: context).optionalize.any
-            } else {
-                base.initializing(in: context).any
-            }
+            base.initializing(in: context).any
         } else {
             IgnoredInitialization().any
         }

Sources/PluginCore/Variables/Type/MemberGroup.swift

@@ -184,6 +184,7 @@ where Decl.ChildSyntaxInput == Void, Decl.MemberSyntax == PropertyDeclSyntax {
             return
                 input
                 .transformKeysAccordingToStrategy(attachedTo: decl)
+                .addDefaultValueIfInitializerExists()
                 .checkInitializedCodingIgnored(attachedAt: decl)
                 .registerKeyPath(
                     provider: CodedAt(from: input.decl)

Tests/MetaCodableTests/CodableInheritanceTests.swift

@@ -79,7 +79,11 @@ final class CodableInheritanceTests: XCTestCase {
 
                     required init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        self.value = try container.decode(String.self, forKey: CodingKeys.value)
+                        do {
+                            self.value = try container.decodeIfPresent(String.self, forKey: CodingKeys.value) ?? ""
+                        } catch {
+                            self.value = ""
+                        }
                     }
 
                     func encode(to encoder: any Encoder) throws {
@@ -122,7 +126,11 @@ final class CodableInheritanceTests: XCTestCase {
 
                     required init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        self.value = try container.decode(String.self, forKey: CodingKeys.value)
+                        do {
+                            self.value = try container.decodeIfPresent(String.self, forKey: CodingKeys.value) ?? ""
+                        } catch {
+                            self.value = ""
+                        }
                         try super.init(from: decoder)
                     }
 
@@ -161,7 +169,11 @@ final class CodableInheritanceTests: XCTestCase {
 
                     required init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        self.value = try container.decode(String.self, forKey: CodingKeys.value)
+                        do {
+                            self.value = try container.decodeIfPresent(String.self, forKey: CodingKeys.value) ?? ""
+                        } catch {
+                            self.value = ""
+                        }
                         try super.init(from: decoder)
                     }
 

Tests/MetaCodableTests/GroupedMutableVariableTests.swift

@@ -68,12 +68,7 @@ final class GroupedMutableVariableTests: XCTestCase {
                 struct SomeCodable {
                     var one, two: String, three: String = ""
 
-                    init(one: String, two: String) {
-                        self.one = one
-                        self.two = two
-                    }
-
-                    init(one: String, two: String, three: String) {
+                    init(one: String, two: String, three: String = "") {
                         self.one = one
                         self.two = two
                         self.three = three
@@ -85,7 +80,11 @@ final class GroupedMutableVariableTests: XCTestCase {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
                         self.one = try container.decode(String.self, forKey: CodingKeys.one)
                         self.two = try container.decode(String.self, forKey: CodingKeys.two)
-                        self.three = try container.decode(String.self, forKey: CodingKeys.three)
+                        do {
+                            self.three = try container.decodeIfPresent(String.self, forKey: CodingKeys.three) ?? ""
+                        } catch {
+                            self.three = ""
+                        }
                     }
                 }
 
@@ -215,12 +214,7 @@ final class GroupedMutableVariableTests: XCTestCase {
                 struct SomeCodable {
                     var one: String, two: String = "", three: Int
 
-                    init(one: String, three: Int) {
-                        self.one = one
-                        self.three = three
-                    }
-
-                    init(one: String, two: String, three: Int) {
+                    init(one: String, two: String = "", three: Int) {
                         self.one = one
                         self.two = two
                         self.three = three
@@ -231,7 +225,11 @@ final class GroupedMutableVariableTests: XCTestCase {
                     init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
                         self.one = try container.decode(String.self, forKey: CodingKeys.one)
-                        self.two = try container.decode(String.self, forKey: CodingKeys.two)
+                        do {
+                            self.two = try container.decodeIfPresent(String.self, forKey: CodingKeys.two) ?? ""
+                        } catch {
+                            self.two = ""
+                        }
                         self.three = try container.decode(Int.self, forKey: CodingKeys.three)
                     }
                 }
@@ -270,12 +268,7 @@ final class GroupedMutableVariableTests: XCTestCase {
                 struct SomeCodable {
                     var one: String, two = "", three: Int
 
-                    init(one: String, three: Int) {
-                        self.one = one
-                        self.three = three
-                    }
-
-                    init(one: String, two: Int, three: Int) {
+                    init(one: String, two: Int = "", three: Int) {
                         self.one = one
                         self.two = two
                         self.three = three
@@ -286,7 +279,11 @@ final class GroupedMutableVariableTests: XCTestCase {
                     init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
                         self.one = try container.decode(String.self, forKey: CodingKeys.one)
-                        self.two = try container.decode(Int.self, forKey: CodingKeys.two)
+                        do {
+                            self.two = try container.decodeIfPresent(Int.self, forKey: CodingKeys.two) ?? ""
+                        } catch {
+                            self.two = ""
+                        }
                         self.three = try container.decode(Int.self, forKey: CodingKeys.three)
                     }
                 }

Tests/MetaCodableTests/IgnoreCodingTests.swift

@@ -295,7 +295,11 @@ final class IgnoreCodingTests: XCTestCase {
                 extension SomeCodable: Decodable {
                     init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        self.one = try container.decode(String.self, forKey: CodingKeys.one)
+                        do {
+                            self.one = try container.decodeIfPresent(String.self, forKey: CodingKeys.one) ?? "some"
+                        } catch {
+                            self.one = "some"
+                        }
                         self.two = try container.decode(String.self, forKey: CodingKeys.two)
                     }
                 }
@@ -398,10 +402,30 @@ final class IgnoreCodingTests: XCTestCase {
                 extension SomeCodable: Decodable {
                     init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        let deeply_container = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.deeply)
-                        let nested_deeply_container = try deeply_container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.nested)
-                        self.four = try nested_deeply_container.decode(String.self, forKey: CodingKeys.two)
-                        self.three = try nested_deeply_container.decode(String.self, forKey: CodingKeys.three)
+                        if let deeply_container = try? container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.deeply) {
+                            if let nested_deeply_container = try? deeply_container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.nested) {
+                                do {
+                                    self.four = try nested_deeply_container.decodeIfPresent(String.self, forKey: CodingKeys.two) ?? "some"
+                                } catch {
+                                    self.four = "some"
+                                }
+                                do {
+                                    self.three = try nested_deeply_container.decodeIfPresent(String.self, forKey: CodingKeys.three) ?? "some"
+                                } catch {
+                                    self.three = "some"
+                                }
+                            } else {
+                                self.one = "some"
+                                self.two = "some"
+                                self.four = "some"
+                                self.three = "some"
+                            }
+                        } else {
+                            self.one = "some"
+                            self.two = "some"
+                            self.four = "some"
+                            self.three = "some"
+                        }
                     }
                 }
 
@@ -457,10 +481,30 @@ final class IgnoreCodingTests: XCTestCase {
 
                     required init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        let deeply_container = try container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.deeply)
-                        let nested_deeply_container = try deeply_container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.nested)
-                        self.four = try nested_deeply_container.decode(String.self, forKey: CodingKeys.two)
-                        self.three = try nested_deeply_container.decode(String.self, forKey: CodingKeys.three)
+                        if let deeply_container = try? container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.deeply) {
+                            if let nested_deeply_container = try? deeply_container.nestedContainer(keyedBy: CodingKeys.self, forKey: CodingKeys.nested) {
+                                do {
+                                    self.four = try nested_deeply_container.decodeIfPresent(String.self, forKey: CodingKeys.two) ?? "some"
+                                } catch {
+                                    self.four = "some"
+                                }
+                                do {
+                                    self.three = try nested_deeply_container.decodeIfPresent(String.self, forKey: CodingKeys.three) ?? "some"
+                                } catch {
+                                    self.three = "some"
+                                }
+                            } else {
+                                self.one = "some"
+                                self.two = "some"
+                                self.four = "some"
+                                self.three = "some"
+                            }
+                        } else {
+                            self.one = "some"
+                            self.two = "some"
+                            self.four = "some"
+                            self.three = "some"
+                        }
                     }
 
                     func encode(to encoder: any Encoder) throws {

Tests/MetaCodableTests/IgnoreInitializedTests.swift

@@ -298,7 +298,11 @@ final class IgnoreInitializedTests: XCTestCase {
                 extension SomeCodable: Decodable {
                     init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        self.one = try container.decode(String.self, forKey: CodingKeys.one)
+                        do {
+                            self.one = try container.decodeIfPresent(String.self, forKey: CodingKeys.one) ?? "some"
+                        } catch {
+                            self.one = "some"
+                        }
                     }
                 }
 
@@ -376,7 +380,11 @@ final class IgnoreInitializedTests: XCTestCase {
                 extension SomeCodable: Decodable {
                     init(from decoder: any Decoder) throws {
                         let container = try decoder.container(keyedBy: CodingKeys.self)
-                        self.one = try container.decode(String.self, forKey: CodingKeys.one)
+                        do {
+                            self.one = try container.decodeIfPresent(String.self, forKey: CodingKeys.one) ?? "some"
+                        } catch {
+                            self.one = "some"
+                        }
                     }
                 }