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Add example macros for member-attribute, member, and accessor macros
Note that this change requires some in-flight fixes that haven't made it to a snapshot release yet.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,85 @@ | ||
| import SwiftSyntax | ||
| import SwiftSyntaxMacros | ||
|
|
||
| public struct DictionaryStorageMacro { } | ||
|
|
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| extension DictionaryStorageMacro: AccessorMacro { | ||
| public static func expansion< | ||
| Context: MacroExpansionContext, | ||
| Declaration: DeclSyntaxProtocol | ||
| >( | ||
| of node: AttributeSyntax, | ||
| providingAccessorsOf declaration: Declaration, | ||
| in context: Context | ||
| ) throws -> [AccessorDeclSyntax] { | ||
| guard let varDecl = declaration.as(VariableDeclSyntax.self), | ||
| let binding = varDecl.bindings.first, | ||
| let identifier = binding.pattern.as(IdentifierPatternSyntax.self)?.identifier, | ||
| binding.accessor == nil, | ||
| let type = binding.typeAnnotation?.type | ||
| else { | ||
| return [] | ||
| } | ||
|
|
||
| // Ignore the "_storage" variable. | ||
| if identifier.text == "_storage" { | ||
| return [] | ||
| } | ||
|
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| guard let defaultValue = binding.initializer?.value else { | ||
| throw CustomError.message("stored property must have an initializer") | ||
| } | ||
|
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| print(varDecl.recursiveDescription) | ||
| return [ | ||
| """ | ||
| get { | ||
| _storage[\(literal: identifier.text), default: \(defaultValue)] as! \(type) | ||
| } | ||
| """, | ||
| """ | ||
| set { | ||
| _storage[\(literal: identifier.text)] = newValue | ||
| } | ||
| """, | ||
| ] | ||
| } | ||
| } | ||
|
|
||
| extension DictionaryStorageMacro: MemberMacro { | ||
| public static func expansion( | ||
| of node: AttributeSyntax, | ||
| providingMembersOf declaration: some DeclGroupSyntax, | ||
| in context: some MacroExpansionContext | ||
| ) throws -> [DeclSyntax] { | ||
| let storage: DeclSyntax = "var _storage: [String: Any] = [:]" | ||
| return [ | ||
| storage.with(\.leadingTrivia, [.newlines(1), .spaces(2)]) | ||
| ] | ||
| } | ||
| } | ||
|
|
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| extension DictionaryStorageMacro: MemberAttributeMacro { | ||
| public static func expansion( | ||
| of node: AttributeSyntax, attachedTo declaration: some DeclGroupSyntax, | ||
| providingAttributesFor member: DeclSyntax, | ||
| in context: some MacroExpansionContext | ||
| ) throws -> [AttributeSyntax] { | ||
| guard let property = member.as(VariableDeclSyntax.self), | ||
| property.isStoredProperty | ||
| else { | ||
| return [] | ||
| } | ||
|
|
||
| return [ | ||
| AttributeSyntax( | ||
| attributeName: SimpleTypeIdentifierSyntax( | ||
| name: .identifier("DictionaryStorage") | ||
| ) | ||
| ) | ||
| .with(\.leadingTrivia, [.newlines(1), .spaces(2)]) | ||
| ] | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,99 @@ | ||
| import SwiftSyntax | ||
| import SwiftSyntaxBuilder | ||
| import SwiftSyntaxMacros | ||
|
|
||
| /// Implementation of the `wrapStoredProperties` macro, which can be | ||
| /// used to apply an attribute to all of the stored properties of a type. | ||
| /// | ||
| /// This macro demonstrates member-attribute macros, which allow an attribute | ||
| /// written on a type or extension to apply attributes to the members | ||
| /// declared within that type or extension. | ||
| public struct WrapStoredPropertiesMacro: MemberAttributeMacro { | ||
| public static func expansion< | ||
| Declaration: DeclGroupSyntax, | ||
| Context: MacroExpansionContext | ||
| >( | ||
| of node: AttributeSyntax, | ||
| attachedTo decl: Declaration, | ||
| providingAttributesFor member: DeclSyntax, | ||
| in context: Context | ||
| ) throws -> [AttributeSyntax] { | ||
| guard let property = member.as(VariableDeclSyntax.self), | ||
| property.isStoredProperty | ||
| else { | ||
| return [] | ||
| } | ||
|
|
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| guard case let .argumentList(arguments) = node.argument, | ||
| let firstElement = arguments.first, | ||
| let stringLiteral = firstElement.expression | ||
| .as(StringLiteralExprSyntax.self), | ||
| stringLiteral.segments.count == 1, | ||
| case let .stringSegment(wrapperName)? = stringLiteral.segments.first else { | ||
| throw CustomError.message("macro requires a string literal containing the name of an attribute") | ||
| } | ||
|
|
||
| return [ | ||
| AttributeSyntax( | ||
| attributeName: SimpleTypeIdentifierSyntax( | ||
| name: .identifier(wrapperName.content.text) | ||
| ) | ||
| ) | ||
| .with(\.leadingTrivia, [.newlines(1), .spaces(2)]) | ||
| ] | ||
| } | ||
| } | ||
|
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| extension VariableDeclSyntax { | ||
| /// Determine whether this variable has the syntax of a stored property. | ||
| /// | ||
| /// This syntactic check cannot account for semantic adjustments due to, | ||
| /// e.g., accessor macros or property wrappers. | ||
| var isStoredProperty: Bool { | ||
| if bindings.count != 1 { | ||
| return false | ||
| } | ||
|
|
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| let binding = bindings.first! | ||
| switch binding.accessor { | ||
| case .none: | ||
| return true | ||
|
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| case .accessors(let node): | ||
| for accessor in node.accessors { | ||
| switch accessor.accessorKind.tokenKind { | ||
| case .keyword(.willSet), .keyword(.didSet): | ||
| // Observers can occur on a stored property. | ||
| break | ||
|
|
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| default: | ||
| // Other accessors make it a computed property. | ||
| return false | ||
| } | ||
| } | ||
|
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| return true | ||
|
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| case .getter: | ||
| return false | ||
|
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| @unknown default: | ||
| return false | ||
| } | ||
| } | ||
| } | ||
|
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| extension DeclGroupSyntax { | ||
| /// Enumerate the stored properties that syntactically occur in this | ||
| /// declaration. | ||
| func storedProperties() -> [VariableDeclSyntax] { | ||
| return members.members.compactMap { member in | ||
| guard let variable = member.decl.as(VariableDeclSyntax.self), | ||
| variable.isStoredProperty else { | ||
| return nil | ||
| } | ||
|
|
||
| return variable | ||
| } | ||
| } | ||
| } |
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