feat: added CodingKey alias support

Author: soumyamahunt

Sources/CodableMacroPlugin/Attributes/CodedAs.swift

@@ -1,4 +1,5 @@
 @_implementationOnly import SwiftSyntax
+@_implementationOnly import SwiftSyntaxMacros
 
 /// Attribute type for `CodedAs` macro-attribute.
 ///
@@ -11,9 +12,9 @@ struct CodedAs: PropertyAttribute {
     let node: AttributeSyntax
 
     /// The alternate value expression provided.
-    var expr: ExprSyntax? {
+    var exprs: [ExprSyntax] {
         return node.arguments?
-            .as(LabeledExprListSyntax.self)?.first?.expression
+            .as(LabeledExprListSyntax.self)?.map(\.expression) ?? []
     }
 
     /// The type to which to be decoded/encoded.
@@ -53,32 +54,62 @@ struct CodedAs: PropertyAttribute {
     ///   * This attribute mustn't be combined with `CodedBy`
     ///     attribute.
     /// * If macro has one argument provided:
-    ///   * Attached declaration is an enum-case declaration.
+    ///   * Attached declaration is an enum-case or variable declaration.
     ///   * This attribute isn't used combined with `IgnoreCoding`
     ///     attribute.
+    /// * If macro attached declaration is variable declaration:
+    ///   * Attached declaration is not a grouped variable declaration.
+    ///   * Attached declaration is not a static variable declaration.
     ///
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
             cantDuplicate()
             `if`(
-                has(arguments: 1),
+                has(arguments: 0),
                 AggregatedDiagnosticProducer {
-                    expect(syntaxes: EnumCaseDeclSyntax.self)
-                    cantBeCombined(with: IgnoreCoding.self)
-                },
-                else: AggregatedDiagnosticProducer {
                     expect(syntaxes: EnumDeclSyntax.self)
                     mustBeCombined(with: Codable.self)
                     mustBeCombined(with: CodedAt.self)
                     cantBeCombined(with: CodedBy.self)
-                }
+                },
+                else: `if`(
+                    isVariable,
+                    AggregatedDiagnosticProducer {
+                        attachedToUngroupedVariable()
+                        attachedToNonStaticVariable()
+                        cantBeCombined(with: IgnoreCoding.self)
+                    },
+                    else: AggregatedDiagnosticProducer {
+                        expect(
+                            syntaxes: EnumCaseDeclSyntax.self,
+                            VariableDeclSyntax.self
+                        )
+                        cantBeCombined(with: IgnoreCoding.self)
+                    }
+                )
             )
         }
     }
 }
 
-extension Registration where Key == ExprSyntax?, Decl: AttributableDeclSyntax {
+extension CodedAs: KeyPathProvider {
+    /// Indicates whether `CodingKey` path
+    /// data is provided to this instance.
+    ///
+    /// Always `true` for this type.
+    var provided: Bool { true }
+
+    /// Updates `CodingKey` path using the provided path.
+    ///
+    /// The `CodingKey` path overrides current `CodingKey` path data.
+    ///
+    /// - Parameter path: Current `CodingKey` path.
+    /// - Returns: Updated `CodingKey` path.
+    func keyPath(withExisting path: [String]) -> [String] { providedPath }
+}
+
+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
@@ -88,9 +119,37 @@ extension Registration where Key == ExprSyntax?, Decl: AttributableDeclSyntax {
     /// - Returns: Newly built registration with value expression data.
     func checkForAlternateValue() -> Self {
         guard
-            self.key == nil,
+            self.key.isEmpty,
             let attr = CodedAs(from: self.decl)
         else { return self }
-        return self.updating(with: attr.expr)
+        return self.updating(with: attr.exprs)
+    }
+}
+
+extension Registration
+where Key == [String], Decl: AttributableDeclSyntax, Var: PropertyVariable {
+    /// Update registration with alternate `CodingKey`s data.
+    ///
+    /// New registration is updated with `CodingKey`s data that will be
+    /// used for decoding/encoding, if provided.
+    ///
+    /// - Parameters:
+    ///   - codingKeys: The `CodingKeys` map new data will be added.
+    ///   - context: The context in which to perform the macro expansion.
+    ///
+    /// - Returns:  Newly built registration with additional `CodingKey`s data.
+    func checkForAlternateKeyValues(
+        addTo codingKeys: CodingKeysMap,
+        context: some MacroExpansionContext
+    ) -> Registration<Decl, Key, AnyPropertyVariable<Var.Initialization>> {
+        guard
+            let attr = CodedAs(from: self.decl),
+            case let path = attr.providedPath,
+            !path.isEmpty
+        else { return self.updating(with: self.variable.any) }
+        let keys = codingKeys.add(keys: path, context: context)
+        let oldVar = self.variable
+        let newVar = AliasedPropertyVariable(base: oldVar, additionalKeys: keys)
+        return self.updating(with: newVar.any)
     }
 }

Sources/CodableMacroPlugin/Attributes/IgnoreCoding/IgnoreCoding.swift

@@ -34,8 +34,8 @@ struct IgnoreCoding: PropertyAttribute {
     /// * 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.
+    /// * This attribute isn't used combined with `CodedIn`,
+    ///  `CodedAt` and `CodedAs` attribute.
     /// * Additionally, warning generated if macro usage is duplicated
     ///   for the same declaration.
     ///
@@ -44,6 +44,7 @@ struct IgnoreCoding: PropertyAttribute {
         return AggregatedDiagnosticProducer {
             cantBeCombined(with: CodedIn.self)
             cantBeCombined(with: CodedAt.self)
+            cantBeCombined(with: CodedAs.self)
             shouldNotDuplicate()
             `if`(
                 isVariable, attachedToInitializedVariable(),

Sources/CodableMacroPlugin/Attributes/KeyPath/CodedAt.swift

@@ -41,7 +41,7 @@ struct CodedAt: PropertyAttribute {
     ///   * Attached declaration is not a grouped variable
     ///     declaration.
     ///   * Attached declaration is not a static variable
-    ///     declaration
+    ///     declaration.
     ///   * This attribute isn't used combined with `CodedIn`
     ///     and `IgnoreCoding` attribute.
     ///

Sources/CodableMacroPlugin/Diagnostics/Condition/ArgumentCountCondition.swift

@@ -24,11 +24,8 @@ struct ArgumentCountCondition<Attr>: DiagnosticCondition where Attr: Attribute {
     /// - Parameter syntax: The syntax to validate.
     /// - Returns: Whether syntax passes validation.
     func satisfied(by syntax: some SyntaxProtocol) -> Bool {
-        guard
-            let args = attr.node.arguments?.as(LabeledExprListSyntax.self),
-            args.count == expected
-        else { return false }
-        return true
+        return expected == attr.node.arguments?
+            .as(LabeledExprListSyntax.self)?.count ?? 0
     }
 }
 

Sources/CodableMacroPlugin/Variables/ComposedVariable.swift

@@ -79,13 +79,34 @@ extension ComposedVariable where Self: ValuedVariable, Wrapped: ValuedVariable {
     var value: ExprSyntax? { base.value }
 }
 
+extension ComposedVariable
+where Self: ConditionalVariable, Wrapped: ConditionalVariable {
+    /// Whether the variable is to be decoded.
+    ///
+    /// Whether underlying wrapped variable is to be decoded.
+    var decode: Bool? { base.decode }
+    /// Whether the variable is to be encoded.
+    ///
+    /// Whether underlying wrapped variable is to be encoded.
+    var encode: Bool? { base.encode }
+}
+
 extension ComposedVariable
 where Self: PropertyVariable, Wrapped: PropertyVariable {
     /// The type of the variable.
     ///
     /// Provides type of the underlying variable value.
     var type: TypeSyntax { base.type }
 
+    /// Whether the variable type requires `Decodable` conformance.
+    ///
+    /// Whether underlying wrapped variable requires `Decodable` conformance.
+    var requireDecodable: Bool? { base.requireDecodable }
+    /// Whether the variable type requires `Encodable` conformance.
+    ///
+    /// Whether underlying wrapped variable requires `Encodable` conformance.
+    var requireEncodable: Bool? { base.requireEncodable }
+
     /// The prefix token to use along with `name` when decoding.
     ///
     /// Provides decode prefix of the underlying variable value.

Sources/CodableMacroPlugin/Variables/Enum/AdjacentlyTaggedEnumSwitcher.swift

@@ -40,23 +40,23 @@ where Wrapped: AdjacentlyTaggableSwitcher {
         self.base = base.registering(variable: variable, keyPath: keys)
     }
 
-    /// Creates value expression for provided enum-case variable.
+    /// Creates value expressions for provided enum-case variable.
     ///
     /// Provides value generated by the underlying variable value.
     ///
     /// - Parameters:
     ///   - variable: The variable for which generated.
-    ///   - value: The optional value present in syntax.
+    ///   - values: The values present in syntax.
     ///   - codingKeys: The map where `CodingKeys` maintained.
     ///   - context: The context in which to perform the macro expansion.
     ///
     /// - Returns: The generated value.
     func keyExpression<Var: EnumCaseVariable>(
-        for variable: Var, value: ExprSyntax?,
+        for variable: Var, values: [ExprSyntax],
         codingKeys: CodingKeysMap, context: some MacroExpansionContext
     ) -> EnumVariable.CaseValue {
         return base.keyExpression(
-            for: variable, value: value,
+            for: variable, values: values,
             codingKeys: codingKeys, context: context
         )
     }

Sources/CodableMacroPlugin/Variables/Enum/AnyEnumSwitcher.swift

@@ -14,23 +14,23 @@ struct AnyEnumSwitcher: EnumSwitcherVariable {
     /// operators (`as?`, `as!`, or `as`).
     let base: any EnumSwitcherVariable
 
-    /// Creates value expression for provided enum-case variable.
+    /// Creates value expressions for provided enum-case variable.
     ///
     /// Provides value generated by the underlying variable value.
     ///
     /// - Parameters:
     ///   - variable: The variable for which generated.
-    ///   - value: The optional value present in syntax.
+    ///   - values: The values present in syntax.
     ///   - codingKeys: The map where `CodingKeys` maintained.
     ///   - context: The context in which to perform the macro expansion.
     ///
     /// - Returns: The generated value.
     func keyExpression<Var: EnumCaseVariable>(
-        for variable: Var, value: SwiftSyntax.ExprSyntax?,
+        for variable: Var, values: [ExprSyntax],
         codingKeys: CodingKeysMap, context: some MacroExpansionContext
     ) -> EnumVariable.CaseValue {
         return base.keyExpression(
-            for: variable, value: value,
+            for: variable, values: values,
             codingKeys: codingKeys, context: context
         )
     }

Sources/CodableMacroPlugin/Variables/Enum/BasicAssociatedVariable.swift

@@ -19,24 +19,6 @@ struct BasicAssociatedVariable: AssociatedVariable, ComposedVariable,
     /// initialization of this variable.
     let label: TokenSyntax?
 
-    /// Whether the variable is to be decoded.
-    ///
-    /// Whether underlying wrapped variable is to be decoded.
-    var decode: Bool? { base.decode }
-    /// Whether the variable is to be encoded.
-    ///
-    /// Whether underlying wrapped variable is to be encoded.
-    var encode: Bool? { base.encode }
-
-    /// Whether the variable type requires `Decodable` conformance.
-    ///
-    /// Whether underlying wrapped variable requires `Decodable` conformance.
-    var requireDecodable: Bool? { base.requireDecodable }
-    /// Whether the variable type requires `Encodable` conformance.
-    ///
-    /// Whether underlying wrapped variable requires `Encodable` conformance.
-    var requireEncodable: Bool? { base.requireEncodable }
-
     /// Creates a new variable from declaration and expansion context.
     ///
     /// Uses the declaration to read variable specific data,

Sources/CodableMacroPlugin/Variables/Enum/BasicEnumCaseVariable.swift

@@ -102,9 +102,15 @@ struct BasicEnumCaseVariable: EnumCaseVariable {
         in context: some MacroExpansionContext,
         from location: EnumCaseCodingLocation
     ) -> SwitchCaseSyntax {
-        let value = location.value
-        let pattern = ExpressionPatternSyntax(expression: value)
-        let label = SwitchCaseLabelSyntax { .init(pattern: pattern) }
+        let firstKey = location.values.first!
+        let label = SwitchCaseLabelSyntax(
+            caseItems: .init {
+                for value in location.values {
+                    let pattern = ExpressionPatternSyntax(expression: value)
+                    SwitchCaseItemSyntax.init(pattern: pattern)
+                }
+            }
+        )
         let caseArgs = variables.map { variable in
             let decode = (variable.decode ?? true)
             let expr: ExprSyntax = decode ? "\(variable.name)" : variable.value!
@@ -118,12 +124,25 @@ struct BasicEnumCaseVariable: EnumCaseVariable {
         switch location.data {
         case .container(let container):
             contentCoder = "contentDecoder"
-            prefix = """
-                let \(contentCoder) = try \(container).superDecoder(forKey: \(value))
-                """
+            prefix = CodeBlockItemListSyntax {
+                if location.values.count > 1 {
+                    let keyName: TokenSyntax = "identifierKey"
+                    let keyList = ArrayExprSyntax(expressions: location.values)
+                    """
+                    let \(keyName) = \(keyList).first { \(container).allKeys.contains($0) } ?? \(firstKey)
+                    """
+                    """
+                    let \(contentCoder) = try \(container).superDecoder(forKey: \(keyName))
+                    """
+                } else {
+                    """
+                    let \(contentCoder) = try \(container).superDecoder(forKey: \(firstKey))
+                    """
+                }
+            }
         case .coder(let coder, let callback):
             contentCoder = coder
-            prefix = callback("\(value)")
+            prefix = callback("\(firstKey)")
         }
         return SwitchCaseSyntax(label: .case(label)) {
             prefix
@@ -160,7 +179,7 @@ struct BasicEnumCaseVariable: EnumCaseVariable {
         let expr: ExprSyntax = ".\(name)\(argExpr)"
         let pattern = ExpressionPatternSyntax(expression: expr)
         let label = SwitchCaseLabelSyntax { .init(pattern: pattern) }
-        let value = location.value
+        let value = location.values.first!
         let contentCoder: TokenSyntax
         let prefix: CodeBlockItemListSyntax
         switch location.data {

Sources/CodableMacroPlugin/Variables/Enum/EnumCaseVariable.swift

@@ -24,8 +24,9 @@ struct EnumCaseCodingLocation {
     /// Represents the data related to switch statement
     /// of enum passed to each case.
     let data: EnumSwitcherGenerated.CaseData
-    /// The value of the variable.
+    /// The values of the variable.
     ///
-    /// Represents the actual value that will be decoded/encoded.
-    let value: ExprSyntax
+    /// Represents the actual values that will be decoded.
+    /// Only the first value will be encoded.
+    let values: [ExprSyntax]
 }