feat: added DecodedAt and EncodedAt macros for separate decoding and encoding CodingKeys (#138)

Author: soumyamahunt

Sources/MacroPlugin/Definitions.swift

@@ -198,6 +198,72 @@ struct CodedAt: PeerMacro {
     }
 }
 
+/// Attribute type for `DecodedAt` macro-attribute.
+///
+/// This type can validate`DecodedAt` macro-attribute
+/// usage and extract data for `Codable` macro to
+/// generate implementation.
+struct DecodedAt: PeerMacro {
+    /// Provide metadata to `Codable` macro for final expansion
+    /// and verify proper usage of this macro.
+    ///
+    /// This macro doesn't perform any expansion rather `Codable` macro
+    /// uses when performing expansion.
+    ///
+    /// This macro verifies that macro usage condition is met by attached
+    /// declaration by using the `validate` implementation provided.
+    ///
+    /// - Parameters:
+    ///   - node: The attribute describing this macro.
+    ///   - declaration: The declaration this macro attribute is attached to.
+    ///   - context: The context in which to perform the macro expansion.
+    ///
+    /// - Returns: No declaration is returned, only attached declaration is
+    ///            analyzed.
+    static func expansion(
+        of node: AttributeSyntax,
+        providingPeersOf declaration: some DeclSyntaxProtocol,
+        in context: some MacroExpansionContext
+    ) throws -> [DeclSyntax] {
+        return try PluginCore.DecodedAt.expansion(
+            of: node, providingPeersOf: declaration, in: context
+        )
+    }
+}
+
+/// Attribute type for `EncodedAt` macro-attribute.
+///
+/// This type can validate `EncodedAt` macro-attribute
+/// usage and extract data for `Codable` macro to
+/// generate implementation.
+struct EncodedAt: PeerMacro {
+    /// Provide metadata to `Codable` macro for final expansion
+    /// and verify proper usage of this macro.
+    ///
+    /// This macro doesn't perform any expansion rather `Codable` macro
+    /// uses when performing expansion.
+    ///
+    /// This macro verifies that macro usage condition is met by attached
+    /// declaration by using the `validate` implementation provided.
+    ///
+    /// - Parameters:
+    ///   - node: The attribute describing this macro.
+    ///   - declaration: The declaration this macro attribute is attached to.
+    ///   - context: The context in which to perform the macro expansion.
+    ///
+    /// - Returns: No declaration is returned, only attached declaration is
+    ///            analyzed.
+    static func expansion(
+        of node: AttributeSyntax,
+        providingPeersOf declaration: some DeclSyntaxProtocol,
+        in context: some MacroExpansionContext
+    ) throws -> [DeclSyntax] {
+        return try PluginCore.EncodedAt.expansion(
+            of: node, providingPeersOf: declaration, in: context
+        )
+    }
+}
+
 /// Attribute type for `CodedIn` macro-attribute.
 ///
 /// This type can validate`CodedIn` macro-attribute

Sources/MacroPlugin/Plugin.swift

@@ -17,6 +17,8 @@ struct MetaCodablePlugin: CompilerPlugin {
         Default.self,
         CodedAs.self,
         ContentAt.self,
+        DecodedAt.self,
+        EncodedAt.self,
         IgnoreCoding.self,
         IgnoreDecoding.self,
         IgnoreEncoding.self,

Sources/MetaCodable/Codable/Decodable.swift

@@ -21,7 +21,7 @@
 ///   * Use ``CodedAt(_:)`` to provide enum-case/protocol identifier tag path.
 ///   * Use ``CodedAs()`` to provide enum-case/protocol identifier tag type.
 ///   * Use ``ContentAt(_:_:)`` to provided enum-case/protocol content path.
-///   * Use ``IgnoreCoding()``, ``IgnoreDecoding()`` to ignore specific 
+///   * Use ``IgnoreCoding()``, ``IgnoreDecoding()`` to ignore specific
 ///     properties/cases/types from decoding.
 ///   * Use ``CodingKeys(_:)`` to work with different case style `CodingKey`s.
 ///   * Use ``IgnoreCodingInitialized()`` to ignore decoding

Sources/MetaCodable/Codable/Encodable.swift

@@ -22,7 +22,7 @@
 ///   * Use ``CodedAt(_:)`` to provide enum-case/protocol identifier tag path.
 ///   * Use ``CodedAs()`` to provide enum-case/protocol identifier tag type.
 ///   * Use ``ContentAt(_:_:)`` to provided enum-case/protocol content path.
-///   * Use ``IgnoreCoding()``, ``IgnoreEncoding()`` to ignore specific 
+///   * Use ``IgnoreCoding()``, ``IgnoreEncoding()`` to ignore specific
 ///     properties/cases/types from encoding.
 ///   * Use ``IgnoreEncoding(if:)-1iuvv`` and ``IgnoreEncoding(if:)-7toka``
 ///     to ignore encoding based on custom conditions.

Sources/MetaCodable/DecodedAt.swift

@@ -0,0 +1,21 @@
+/// Indicates the field needs to be decoded to a specific
+/// `CodingKey` path provided, different from the encoding path.
+///
+/// See ``CodedAt(_:)`` for all configurations and use-cases.
+///
+/// - Parameter path: The `CodingKey` path value located at for decoding only.
+///
+/// - Note: This macro on its own only validates if attached declaration
+///   is a variable declaration. ``Codable(commonStrategies:)`` macro uses this macro
+///   when generating final implementations.
+///
+/// - Important: When applied to fields, the field type must confirm to
+///   `Decodable`.
+///
+/// - Important: This macro affects only decoding operations. Encoding will use
+///   the default variable name or any encoding path specified with ``EncodedAt(_:)``.
+@attached(peer)
+@available(swift 5.9)
+public macro DecodedAt(_ path: StaticString...) = #externalMacro(
+    module: "MacroPlugin", type: "DecodedAt"
+)

Sources/MetaCodable/EncodedAt.swift

@@ -0,0 +1,21 @@
+/// Indicates the field needs to be encoded to a specific
+/// `CodingKey` path provided, different from the decoding path.
+///
+/// See ``CodedAt(_:)`` for all configurations and use-cases.
+///
+/// - Parameter path: The `CodingKey` path value located at for encoding only.
+///
+/// - Note: This macro on its own only validates if attached declaration
+///   is a variable declaration. ``Codable(commonStrategies:)`` macro uses this macro
+///   when generating final implementations.
+///
+/// - Important: When applied to fields, the field type must confirm to
+///   `Encodable`.
+///
+/// - Important: This macro affects only encoding operations. Decoding will use
+///   the default variable name or any encoding path specified with ``DecodedAt(_:)``.
+@attached(peer)
+@available(swift 5.9)
+public macro EncodedAt(_ path: StaticString...) = #externalMacro(
+    module: "MacroPlugin", type: "EncodedAt"
+)

Sources/MetaCodable/MetaCodable.docc/MetaCodable.md

@@ -77,6 +77,8 @@ Supercharge `Swift`'s `Codable` implementations with macros.
 ### Strategies
 
 - ``CodedAt(_:)``
+- ``DecodedAt(_:)``
+- ``EncodedAt(_:)``
 - ``CodedIn(_:)``
 - ``CodedAs()``
 - ``CodedAs(_:_:)``

Sources/PluginCore/Attributes/Codable/CodingKeys/CodingKeys.swift

@@ -59,7 +59,7 @@ package struct CodingKeys: PeerAttribute {
     }
 }
 
-extension Registration where Key == [String] {
+extension Registration where Key == PathKey {
     /// Update current registration `CodingKey` path data.
     ///
     /// New registration is updated with the transformed `CodingKey` path
@@ -72,6 +72,10 @@ extension Registration where Key == [String] {
     ) -> Self where D: AttributableDeclSyntax {
         guard let attr = CodingKeys(from: decl) else { return self }
         let strategy = attr.strategy
-        return self.updating(with: strategy.transform(keyPath: self.key))
+        let newKey = PathKey(
+            decoding: strategy.transform(keyPath: self.key.decoding),
+            encoding: strategy.transform(keyPath: self.key.encoding)
+        )
+        return self.updating(with: newKey)
     }
 }

Sources/PluginCore/Attributes/CodedAs.swift

@@ -72,7 +72,9 @@ package struct CodedAs: PropertyAttribute {
                         syntaxes: EnumDeclSyntax.self, ProtocolDeclSyntax.self
                     )
                     mustBeCombined(with: Codable.self)
-                    mustBeCombined(with: CodedAt.self)
+                    mustBeCombined(
+                        with: CodedAt.self, or: DecodedAt.self, EncodedAt.self
+                    )
                 },
                 else: `if`(
                     isVariable,
@@ -128,7 +130,7 @@ extension Registration where Key == [ExprSyntax], Decl: AttributableDeclSyntax {
 }
 
 extension Registration
-where Key == [String], Decl: AttributableDeclSyntax, Var: PropertyVariable {
+where Decl: AttributableDeclSyntax, Var: PropertyVariable {
     /// Update registration with alternate `CodingKey`s data.
     ///
     /// New registration is updated with `CodingKey`s data that will be

Sources/PluginCore/Attributes/CodedBy.swift

@@ -54,7 +54,9 @@ package struct CodedBy: PropertyAttribute {
                 isEnum || isProtocol,
                 AggregatedDiagnosticProducer {
                     mustBeCombined(with: Codable.self)
-                    mustBeCombined(with: CodedAt.self)
+                    mustBeCombined(
+                        with: CodedAt.self, or: DecodedAt.self, EncodedAt.self
+                    )
                 },
                 else: AggregatedDiagnosticProducer {
                     expect(syntaxes: VariableDeclSyntax.self)