feat: support @EncodingIgnored and @DecodingIgnored (#40)

vnixx · web-flow · commit ef5dc1e7dda1 · 2026-03-11T17:38:33.000+08:00
diff --git a/README.md b/README.md
@@ -40,7 +40,7 @@ Main features include:
 - Customize nested containers during Coding using `@CodingContainer`
 - Support specified `CodingKey` for Encode, like `EncodingKey("encode_key")`
 - Allow using default values when decoding fails to avoid `keyNotFound` errors
-- Allow using `@CodingIgnored` to ignore specific properties during encoding/decoding
+- Allow using `@CodingIgnored`, `@EncodingIgnored`, and `@DecodingIgnored` to ignore specific properties during coding
 - Support automatic conversion between base64 strings and `Data` `[UInt8]` types using `@Base64Coding`
 - Through `@CompactDecoding`, ignore `null` values when Decoding `Array`, `Dictionary`, `Set` instead of throwing errors
 - Support various encoding/decoding of `Date` through `@DateCoding`
@@ -333,15 +333,21 @@ struct Preferences {
 
 ### 8. Ignore Properties
 
-Use `@CodingIgnored` to ignore specific properties during encoding/decoding. During decoding, non-`Optional` properties must have a default value to satisfy Swift initialization requirements. `ReerCodable` automatically generates default values for basic data types and collection types. For other custom types, users need to provide default values.
+Use `@CodingIgnored` to ignore properties during both encoding and decoding, `@EncodingIgnored` to ignore properties only during encoding, and `@DecodingIgnored` to ignore properties only during decoding. When decoding is ignored, non-`Optional` properties must have a default value to satisfy Swift initialization requirements. `ReerCodable` automatically generates default values for basic data types and collection types. For other custom types, users need to provide default values.
 
 ```swift
 @Codable
 struct User {
     var name: String
-    
+
     @CodingIgnored
-    var ignore: Set<String>
+    var transient: Set<String>
+
+    @EncodingIgnored
+    var serverToken: String
+
+    @DecodingIgnored
+    var localDraft: String = "draft"
 }
 ```
 
diff --git a/README_CN.md b/README_CN.md
@@ -35,7 +35,7 @@ ReerCodable 框架提供了一系列自定义宏，用于生成动态的 Codable
 - 通过使用 `@CodingContainer` 自定义 Coding 时的嵌套容器 
 - 支持 Encode 时指定的 `CodingKey`, 如 `EncodingKey("encode_key")`
 - 允许解码失败时使用默认值, 从而避免 `keyNotFound` 错误发生
-- 允许使用 `@CodingIgnored` 在编解码过程中忽略特定属性
+- 允许使用 `@CodingIgnored`、`@EncodingIgnored`、`@DecodingIgnored` 在编解码过程中按需忽略特定属性
 - 支持使用 `@Base64Coding` 自动对 base64 字符串和 `Data` `[UInt8]` 类型进行转换
 - 在 Decode `Array`, `Dictionary`, `Set` 时, 通过 `@CompactDecoding` 可以忽略 `null` 值, 而不是抛出错误
 - 支持通过 `@DateCoding` 实现对 `Date` 的各种编解码
@@ -327,15 +327,21 @@ struct Preferences {
 
 ### 8. 忽略属性
 
-使用 `@CodingIgnored` 在编解码过程中忽略特定属性. 在解码过程中对于非 `Optional` 属性要有一个默认值才能满足 Swift 初始化的要求, `ReerCodable` 对基本数据类型和集合类型会自动生成默认值, 如果是其他自定义类型, 则需用用户提供默认值.
+使用 `@CodingIgnored` 可以同时在编码和解码时忽略属性, `@EncodingIgnored` 只在编码时忽略, `@DecodingIgnored` 只在解码时忽略. 当属性会被解码侧忽略时, 对于非 `Optional` 属性要有一个默认值才能满足 Swift 初始化的要求, `ReerCodable` 对基本数据类型和集合类型会自动生成默认值, 如果是其他自定义类型, 则需由用户提供默认值.
 
 ```swift
 @Codable
 struct User {
     var name: String
-    
+
     @CodingIgnored
-    var ignore: Set<String>
+    var transient: Set<String>
+
+    @EncodingIgnored
+    var serverToken: String
+
+    @DecodingIgnored
+    var localDraft: String = "draft"
 }
 ```
 
diff --git a/Sources/ReerCodable/MacroDeclarations/CodingIgnored.swift b/Sources/ReerCodable/MacroDeclarations/CodingIgnored.swift
@@ -38,3 +38,20 @@
 /// ```
 @attached(peer)
 public macro CodingIgnored() = #externalMacro(module: "ReerCodableMacros", type: "CodingIgnored")
+
+/// The `@EncodingIgnored` macro marks a property to be ignored during encoding only.
+///
+/// When applied to a property in a type marked with `@Codable`, this property will be:
+/// - Skipped during encoding (not written to the encoded data)
+/// - Still participate in decoding as usual
+@attached(peer)
+public macro EncodingIgnored() = #externalMacro(module: "ReerCodableMacros", type: "EncodingIgnored")
+
+/// The `@DecodingIgnored` macro marks a property to be ignored during decoding only.
+///
+/// When applied to a property in a type marked with `@Codable`, this property will be:
+/// - Skipped during decoding (not read from the encoded data)
+/// - Still participate in encoding as usual
+/// - Initialized with its default value or nil if optional
+@attached(peer)
+public macro DecodingIgnored() = #externalMacro(module: "ReerCodableMacros", type: "DecodingIgnored")
diff --git a/Sources/ReerCodableMacros/MacroImplementations/CustomCodingImpl.swift b/Sources/ReerCodableMacros/MacroImplementations/CustomCodingImpl.swift
@@ -34,6 +34,8 @@ public struct CustomCoding: PeerMacro {
         if variable.attributes.count > 1 {
             let incompatibleMacros = [
                 "CodingIgnored",
+                "EncodingIgnored",
+                "DecodingIgnored",
                 "Base64Coding",
                 "DateCoding",
                 "CompactDecoding",
diff --git a/Sources/ReerCodableMacros/MacroImplementations/IgnoreCodingImpl.swift b/Sources/ReerCodableMacros/MacroImplementations/IgnoreCodingImpl.swift
@@ -22,47 +22,109 @@
 import SwiftSyntax
 import SwiftSyntaxMacros
 
+private enum IgnoreCodingMode: Equatable {
+    case both
+    case encoding
+    case decoding
+
+    var macroName: String {
+        switch self {
+        case .both:
+            return "CodingIgnored"
+        case .encoding:
+            return "EncodingIgnored"
+        case .decoding:
+            return "DecodingIgnored"
+        }
+    }
+
+    var diagnosticPrefix: String {
+        "@\(macroName) macro"
+    }
+}
+
+private func validateIgnoredProperty(
+    declaration: some DeclSyntaxProtocol,
+    mode: IgnoreCodingMode
+) throws {
+    guard
+        let variable = declaration.as(VariableDeclSyntax.self),
+        let name = variable.name
+    else {
+        throw MacroError(text: "\(mode.diagnosticPrefix) is only for property.")
+    }
+
+    let ignoreMacros = ["CodingIgnored", "EncodingIgnored", "DecodingIgnored"]
+    let usedIgnoreMacros = ignoreMacros.filter { variable.attributes.containsAttribute(named: $0) }
+    if usedIgnoreMacros.count > 1 {
+        throw MacroError(
+            text: "\(mode.diagnosticPrefix) cannot be used together with @\(usedIgnoreMacros.filter { $0 != mode.macroName }.joined(separator: ", @"))."
+        )
+    }
+
+    if mode == .encoding, variable.attributes.containsAttribute(named: "EncodingKey") {
+        throw MacroError(text: "@EncodingIgnored macro cannot be used together with @EncodingKey.")
+    }
+
+    if mode != .encoding {
+        if variable.isOptional {
+            return
+        }
+        if variable.initExpr != nil {
+            return
+        }
+        if let type = variable.type,
+           canGenerateDefaultValue(for: type) {
+            return
+        }
+        throw MacroError(text: "The ignored property `\(name)` should have a default value, or be set as an optional type.")
+    }
+}
+
 public struct CodingIgnored: PeerMacro {
     public static func expansion(
         of node: AttributeSyntax,
         providingPeersOf declaration: some DeclSyntaxProtocol,
         in context: some MacroExpansionContext
     ) throws -> [DeclSyntax] {
-        guard
-            let variable = declaration.as(VariableDeclSyntax.self),
-            let name = variable.name
-        else {
-            throw MacroError(text: "@CodingIgnored macro is only for property.")
-        }
-        
-        if variable.attributes.firstAttribute(named: "CodingIgnored") != nil {
-            if variable.isOptional {
-                return []
-            }
-            if variable.initExpr != nil {
-                return []
-            }
-            if let type = variable.type,
-               canGenerateDefaultValue(for: type) {
-                return []
-            }
-            throw MacroError(text: "The ignored property `\(name)` should have a default value, or be set as an optional type.")
-        }
+        try validateIgnoredProperty(declaration: declaration, mode: .both)
         return []
     }
-    
-    static func canGenerateDefaultValue(for type: String) -> Bool {
-        let trimmed = type.trimmingCharacters(in: .whitespaces)
-        let basicType = [
-            "Int", "Int8", "Int16", "Int32", "Int64", "Int128",
-            "UInt", "UInt8", "UInt16", "UInt32", "UInt64", "UInt128",
-            "Bool", "String", "Float", "Double"
-        ].contains(trimmed)
-        if basicType
-           || (trimmed.hasPrefix("[") && trimmed.hasSuffix("]"))
-           || trimmed.hasPrefix("Set<") {
-            return true
-        }
-        return false
+}
+
+public struct EncodingIgnored: PeerMacro {
+    public static func expansion(
+        of node: AttributeSyntax,
+        providingPeersOf declaration: some DeclSyntaxProtocol,
+        in context: some MacroExpansionContext
+    ) throws -> [DeclSyntax] {
+        try validateIgnoredProperty(declaration: declaration, mode: .encoding)
+        return []
+    }
+}
+
+public struct DecodingIgnored: PeerMacro {
+    public static func expansion(
+        of node: AttributeSyntax,
+        providingPeersOf declaration: some DeclSyntaxProtocol,
+        in context: some MacroExpansionContext
+    ) throws -> [DeclSyntax] {
+        try validateIgnoredProperty(declaration: declaration, mode: .decoding)
+        return []
+    }
+}
+
+func canGenerateDefaultValue(for type: String) -> Bool {
+    let trimmed = type.trimmingCharacters(in: .whitespaces)
+    let basicType = [
+        "Int", "Int8", "Int16", "Int32", "Int64", "Int128",
+        "UInt", "UInt8", "UInt16", "UInt32", "UInt64", "UInt128",
+        "Bool", "String", "Float", "Double"
+    ].contains(trimmed)
+    if basicType
+       || (trimmed.hasPrefix("[") && trimmed.hasSuffix("]"))
+       || trimmed.hasPrefix("Set<") {
+        return true
     }
+    return false
 }
diff --git a/Sources/ReerCodableMacros/Plugins.swift b/Sources/ReerCodableMacros/Plugins.swift
@@ -54,6 +54,8 @@ struct ReerCodablePlugin: CompilerPlugin {
         CodingKey.self,
         EncodingKey.self,
         CodingIgnored.self,
+        EncodingIgnored.self,
+        DecodingIgnored.self,
         DecodingDefault.self,
         EncodingDefault.self,
         CodingDefault.self,
diff --git a/Sources/ReerCodableMacros/PropertyInfo.swift b/Sources/ReerCodableMacros/PropertyInfo.swift
@@ -27,7 +27,8 @@ struct PropertyInfo {
     var name: String
     var type: String
     var isOptional = false
-    var isIgnored = false
+    var ignoreEncoding = false
+    var ignoreDecoding = false
     var keys: [String] = []
     var encodingKey: String?
     var treatDotAsNestedWhenEncoding: Bool = true
diff --git a/Sources/ReerCodableMacros/TypeInfo.swift b/Sources/ReerCodableMacros/TypeInfo.swift
@@ -336,7 +336,14 @@ extension TypeInfo {
                 property.caseStyles = propertyCaseStyles.uniqueMerged(with: caseStyles)
                 // ignore coding
                 if variable.attributes.firstAttribute(named: "CodingIgnored") != nil {
-                    property.isIgnored = true
+                    property.ignoreEncoding = true
+                    property.ignoreDecoding = true
+                }
+                if variable.attributes.firstAttribute(named: "EncodingIgnored") != nil {
+                    property.ignoreEncoding = true
+                }
+                if variable.attributes.firstAttribute(named: "DecodingIgnored") != nil {
+                    property.ignoreDecoding = true
                 }
                 // base64 coding
                 if variable.attributes.containsAttribute(named: "Base64Coding") {
@@ -681,7 +688,7 @@ extension TypeInfo {
         } else {
             assignments = try properties
                 .compactMap { property in
-                    if property.isIgnored {
+                    if property.ignoreDecoding {
                         if property.isOptional { return nil }
                         if let initExpr = property.initExpr {
                             return "self.\(property.name) = \(initExpr)"
@@ -824,7 +831,7 @@ extension TypeInfo {
         } else {
             encoding = properties
                 .compactMap { property in
-                    if property.isIgnored { return nil }
+                    if property.ignoreEncoding { return nil }
                     let valueExpr = property.encodingValueExpr
                     let resolvedValueExpr = property.resolvedEncodingValueExpr
                     let needsOptionalHandling = property.needsOptionalEncodingHandling
@@ -914,7 +921,7 @@ extension TypeInfo {
             text += ": \(property.type)"
             if let initExpr = property.initExpr {
                 text += "= \(initExpr)"
-            } else if property.isIgnored, let defaultValue = property.defaultValue {
+                        } else if property.ignoreDecoding, let defaultValue = property.defaultValue {
                 text += "= \(defaultValue)"
             } else if property.isOptional {
                 text += "= nil"
diff --git a/Tests/ReerCodableTests/MacroExpandTests.swift b/Tests/ReerCodableTests/MacroExpandTests.swift
diff --git a/Tests/ReerCodableTests/PropertyListCodingTests.swift b/Tests/ReerCodableTests/PropertyListCodingTests.swift
diff --git a/Tests/ReerCodableTests/ReerCodableTests.swift b/Tests/ReerCodableTests/ReerCodableTests.swift
