feat: added externally tagged enum support

Author: soumyamahunt

Sources/CodableMacroPlugin/Attributes/Codable/Codable.swift

@@ -40,13 +40,16 @@ struct Codable: Attribute {
     /// attached declaration.
     ///
     /// Builds diagnoser that validates attached declaration
-    /// is `struct` or `class` declaration and macro
+    /// is `struct`/`class`/`enum` declaration and macro
     /// usage is not duplicated for the same declaration.
     ///
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
-            expect(syntaxes: StructDeclSyntax.self, ClassDeclSyntax.self)
+            expect(
+                syntaxes: StructDeclSyntax.self, ClassDeclSyntax.self,
+                EnumDeclSyntax.self
+            )
             cantDuplicate()
         }
     }

Sources/CodableMacroPlugin/Attributes/Codable/CodingKeys/CodingKeys.swift

@@ -43,16 +43,23 @@ struct CodingKeys: PeerAttribute {
     /// has `Codable` macro attached and macro usage
     /// is not duplicated for the same declaration.
     ///
+    /// For enum case declarations this attribute can be attached
+    /// without `Codable` macro.
+    ///
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
-            mustBeCombined(with: Codable.self)
             cantDuplicate()
+            `if`(
+                isStruct || isClass || isEnum,
+                mustBeCombined(with: Codable.self),
+                else: expect(syntaxes: EnumCaseDeclSyntax.self)
+            )
         }
     }
 }
 
-extension Registration {
+extension Registration where Key == [String] {
     /// Update current registration `CodingKey` path data.
     ///
     /// New registration is updated with the transformed `CodingKey` path
@@ -65,6 +72,6 @@ extension Registration {
     ) -> 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.keyPath))
+        return self.updating(with: strategy.transform(keyPath: self.key))
     }
 }

Sources/CodableMacroPlugin/Attributes/Codable/IgnoreCodingInitialized.swift

@@ -36,16 +36,23 @@ struct IgnoreCodingInitialized: PeerAttribute {
     /// has `Codable` macro attached and macro usage
     /// is not duplicated for the same declaration.
     ///
+    /// For enum case declarations this attribute can be attached
+    /// without `Codable` macro.
+    ///
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
-            mustBeCombined(with: Codable.self)
             shouldNotDuplicate()
+            `if`(
+                isStruct || isClass || isEnum,
+                mustBeCombined(with: Codable.self),
+                else: expect(syntaxes: EnumCaseDeclSyntax.self)
+            )
         }
     }
 }
 
-extension Registration where Var: NamedVariable {
+extension Registration where Var: ValuedVariable {
     /// Update registration whether decoding/encoding to be ignored.
     ///
     /// New registration is updated with decoding and encoding condition
@@ -57,7 +64,7 @@ extension Registration where Var: NamedVariable {
     ///   data.
     func checkInitializedCodingIgnored<D: AttributableDeclSyntax>(
         attachedAt decl: D
-    ) -> Registration<Decl, ConditionalCodingVariable<Var>> {
+    ) -> Registration<Decl, Key, ConditionalCodingVariable<Var>> {
         typealias Output = ConditionalCodingVariable<Var>
         let attr = IgnoreCodingInitialized(from: decl)
         let code = attr != nil ? self.variable.value == nil : nil

Sources/CodableMacroPlugin/Attributes/CodedAs.swift

@@ -0,0 +1,69 @@
+@_implementationOnly import SwiftSyntax
+
+/// Attribute type for `CodedAs` macro-attribute.
+///
+/// This type can validate`CodedAs` macro-attribute
+/// usage and extract data for `Codable` macro to
+/// generate implementation.
+struct CodedAs: PropertyAttribute {
+    /// The node syntax provided
+    /// during initialization.
+    let node: AttributeSyntax
+
+    /// The alternate value expression provided.
+    var expr: ExprSyntax {
+        return node.arguments!
+            .as(LabeledExprListSyntax.self)!.first!.expression
+    }
+
+    /// Creates a new instance with the provided node.
+    ///
+    /// The initializer fails to create new instance if the name
+    /// of the provided node is different than this attribute.
+    ///
+    /// - Parameter node: The attribute syntax to create with.
+    /// - Returns: Newly created attribute instance.
+    init?(from node: AttributeSyntax) {
+        guard
+            node.attributeName.as(IdentifierTypeSyntax.self)!
+                .description == Self.name
+        else { return nil }
+        self.node = node
+    }
+
+    /// Builds diagnoser that can validate this macro
+    /// attached declaration.
+    ///
+    /// The following conditions are checked by the
+    /// built diagnoser:
+    /// * Attached declaration is an enum-case declaration.
+    /// * Macro usage is not duplicated for the same declaration.
+    /// * This attribute isn't used combined with `IgnoreCoding`
+    ///   attribute.
+    ///
+    /// - Returns: The built diagnoser instance.
+    func diagnoser() -> DiagnosticProducer {
+        return AggregatedDiagnosticProducer {
+            expect(syntaxes: EnumCaseDeclSyntax.self)
+            cantDuplicate()
+            cantBeCombined(with: IgnoreCoding.self)
+        }
+    }
+}
+
+extension Registration where Key == ExprSyntax?, Decl: AttributableDeclSyntax {
+    /// Update registration with alternate value expression data.
+    ///
+    /// New registration is updated with value expression data that will be
+    /// used for decoding/encoding, if provided and registration doesn't
+    /// already have a value.
+    ///
+    /// - Returns: Newly built registration with value expression data.
+    func checkForAlternateValue() -> Self {
+        guard
+            self.key == nil,
+            let attr = CodedAs(from: self.decl)
+        else { return self }
+        return self.updating(with: attr.expr)
+    }
+}

Sources/CodableMacroPlugin/Attributes/CodedBy.swift

@@ -70,8 +70,8 @@ where
     /// used for decoding/encoding, if provided.
     ///
     /// - Returns: Newly built registration with helper expression data.
-    func useHelperCoderIfExists() -> Registration<Decl, CodedByOutput> {
-        guard let attr = CodedBy(from: self.declaration)
+    func useHelperCoderIfExists() -> Registration<Decl, Key, CodedByOutput> {
+        guard let attr = CodedBy(from: self.decl)
         else { return self.updating(with: self.variable.any) }
         let newVar = self.variable.with(helper: attr.expr)
         return self.updating(with: newVar.any)

Sources/CodableMacroPlugin/Attributes/Default.swift

@@ -69,8 +69,8 @@ where
     /// used for decoding failure and memberwise initializer(s), if provided.
     ///
     /// - Returns: Newly built registration with default expression data.
-    func addDefaultValueIfExists() -> Registration<Decl, DefOutput> {
-        guard let attr = Default(from: self.declaration)
+    func addDefaultValueIfExists() -> Registration<Decl, Key, DefOutput> {
+        guard let attr = Default(from: self.decl)
         else { return self.updating(with: self.variable.any) }
         let newVar = self.variable.with(default: attr.expr)
         return self.updating(with: newVar.any)

Sources/CodableMacroPlugin/Attributes/IgnoreCoding/IgnoreCoding.swift

@@ -30,23 +30,25 @@ struct IgnoreCoding: PropertyAttribute {
     /// Builds diagnoser that can validate this macro
     /// attached declaration.
     ///
-    /// The following conditions are checked by the
-    /// built diagnoser:
-    /// * Attached declaration is a variable declaration.
-    /// * Attached variable declaration has default
-    ///   initialization or variable is a computed property.
-    /// * This attribute isn't used combined with `CodedIn`
-    ///   and `CodedAt` attribute.
-    /// * Additionally, warning generated if macro usage
-    ///   is duplicated for the same declaration.
+    /// The following conditions are checked by the built diagnoser:
+    /// * Attached declaration is a variable or enum case declaration.
+    /// * Attached variable declaration has default initialization or
+    ///   variable is a computed property.
+    /// * This attribute isn't used combined with `CodedIn` and
+    ///  `CodedAt` attribute.
+    /// * Additionally, warning generated if macro usage is duplicated
+    ///   for the same declaration.
     ///
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
-            attachedToInitializedVariable()
             cantBeCombined(with: CodedIn.self)
             cantBeCombined(with: CodedAt.self)
             shouldNotDuplicate()
+            `if`(
+                isVariable, attachedToInitializedVariable(),
+                else: expect(syntaxes: EnumCaseDeclSyntax.self)
+            )
         }
     }
 }
@@ -69,12 +71,11 @@ extension Registration where Decl: AttributableDeclSyntax {
     ///
     /// - Returns: Newly built registration with conditional decoding/encoding
     ///   data.
-    func checkCodingIgnored() -> Registration<Decl, ConditionalOutput> {
+    func checkCodingIgnored() -> Registration<Decl, Key, ConditionalOutput> {
         typealias Output = ConditionalOutput
-        let declaration = self.declaration
-        let ignoreCoding = IgnoreCoding(from: declaration) != nil
-        let ignoreDecoding = IgnoreDecoding(from: declaration) != nil
-        let ignoreEncoding = IgnoreEncoding(from: declaration) != nil
+        let ignoreCoding = IgnoreCoding(from: self.decl) != nil
+        let ignoreDecoding = IgnoreDecoding(from: self.decl) != nil
+        let ignoreEncoding = IgnoreEncoding(from: self.decl) != nil
         let decode = !ignoreCoding && !ignoreDecoding
         let encode = !ignoreCoding && !ignoreEncoding
         let options = Output.Options(decode: decode, encode: encode)

Sources/CodableMacroPlugin/Attributes/IgnoreCoding/IgnoreDecoding.swift

@@ -27,26 +27,26 @@ struct IgnoreDecoding: PropertyAttribute {
         self.node = node
     }
 
-    /// Builds diagnoser that can validate this macro
-    /// attached declaration.
+    /// Builds diagnoser that can validate this macro attached declaration.
     ///
-    /// The following conditions are checked by the
-    /// built diagnoser:
-    /// * Attached declaration is a variable declaration.
-    /// * Attached variable declaration has default
-    ///   initialization or variable is a computed property.
-    /// * Additionally, warning generated if macro usage
-    ///   is duplicated for the same declaration.
-    /// * Additionally, warning also generated if this
-    ///   attribute is used combined with `IgnoreCoding`
-    ///   attribute.
+    /// The following conditions are checked by the built diagnoser:
+    /// * Attached declaration is a variable or enum case declaration.
+    /// * Attached variable declaration has default initialization or
+    ///   variable is a computed property.
+    /// * Additionally, warning generated if macro usage is duplicated
+    ///   for the same declaration.
+    /// * Additionally, warning also generated if this attribute is used
+    ///   combined with `IgnoreCoding` attribute.
     ///
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
-            attachedToInitializedVariable()
             shouldNotDuplicate()
             shouldNotBeCombined(with: IgnoreCoding.self)
+            `if`(
+                isVariable, attachedToInitializedVariable(),
+                else: expect(syntaxes: EnumCaseDeclSyntax.self)
+            )
         }
     }
 }

Sources/CodableMacroPlugin/Attributes/IgnoreCoding/IgnoreEncoding.swift

@@ -27,22 +27,19 @@ struct IgnoreEncoding: PropertyAttribute {
         self.node = node
     }
 
-    /// Builds diagnoser that can validate this macro
-    /// attached declaration.
+    /// Builds diagnoser that can validate this macro attached declaration.
     ///
-    /// The following conditions are checked by the
-    /// built diagnoser:
-    /// * Attached declaration is a variable declaration.
-    /// * Additionally, warning generated if macro usage
-    ///   is duplicated for the same declaration.
-    /// * Additionally, warning also generated if this
-    ///   attribute is used combined with `IgnoreCoding`
-    ///   attribute.
+    /// The following conditions are checked by the built diagnoser:
+    /// * Attached declaration is a variable or enum case declaration.
+    /// * Additionally, warning generated if macro usage is duplicated
+    ///   for the same declaration.
+    /// * Additionally, warning also generated if this attribute is used
+    ///   combined with `IgnoreCoding` attribute.
     ///
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
-            expect(syntaxes: VariableDeclSyntax.self)
+            expect(syntaxes: VariableDeclSyntax.self, EnumCaseDeclSyntax.self)
             shouldNotDuplicate()
             shouldNotBeCombined(with: IgnoreCoding.self)
         }

Sources/CodableMacroPlugin/Attributes/KeyPath/KeyPathProvider.swift

@@ -86,7 +86,7 @@ extension CodedIn: KeyPathProvider {
     }
 }
 
-extension Registration where Decl: AttributableDeclSyntax {
+extension Registration where Key == [String] {
     /// Update registration with `CodingKey` path data.
     ///
     /// New registration is updated with the provided `CodingKey` path from provider,
@@ -96,13 +96,13 @@ extension Registration where Decl: AttributableDeclSyntax {
     /// - Returns: Newly built registration with additional `CodingKey` path data.
     func registerKeyPath(
         provider: KeyPathProvider
-    ) -> Registration<Decl, KeyedVariable<Var>> {
+    ) -> Registration<Decl, Key, KeyedVariable<Var>> {
         typealias Output = KeyedVariable<Var>
         let options = Output.Options(code: provider.provided)
         let newVar = Output(base: self.variable, options: options)
         let output = self.updating(with: newVar)
         guard provider.provided else { return output }
-        let updatedPath = provider.keyPath(withExisting: self.keyPath)
+        let updatedPath = provider.keyPath(withExisting: self.key)
         return output.updating(with: updatedPath)
     }
 }