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Merge pull request DougGregor#6 from hborla/observable-macro
Add an `Observable` macro implementation example.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,150 @@ | ||
| import SwiftSyntax | ||
| import SwiftSyntaxMacros | ||
|
|
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| private extension DeclSyntaxProtocol { | ||
| var isObservableStoredProperty: Bool { | ||
| guard let property = self.as(VariableDeclSyntax.self), | ||
| let binding = property.bindings.first | ||
| else { | ||
| return false | ||
| } | ||
|
|
||
| return binding.accessor == nil | ||
| } | ||
| } | ||
|
|
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| public struct ObservableMacro: MemberMacro, MemberAttributeMacro { | ||
|
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| // MARK: - MemberMacro | ||
|
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| public static func expansion( | ||
| of node: AttributeSyntax, | ||
| providingMembersOf declaration: some DeclGroupSyntax, | ||
| in context: some MacroExpansionContext | ||
| ) throws -> [DeclSyntax] { | ||
| guard let identified = declaration.asProtocol(IdentifiedDeclSyntax.self) else { | ||
| return [] | ||
| } | ||
|
|
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| let parentName = identified.identifier | ||
|
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| let registrar: DeclSyntax = | ||
| """ | ||
| let _registrar = ObservationRegistrar<\(parentName)>() | ||
| """ | ||
|
|
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| let addObserver: DeclSyntax = | ||
| """ | ||
| public nonisolated func addObserver(_ observer: some Observer<\(parentName)>) { | ||
| _registrar.addObserver(observer) | ||
| } | ||
| """ | ||
|
|
||
| let removeObserver: DeclSyntax = | ||
| """ | ||
| public nonisolated func removeObserver(_ observer: some Observer<\(parentName)>) { | ||
| _registrar.removeObserver(observer) | ||
| } | ||
| """ | ||
|
|
||
| let withTransaction: DeclSyntax = | ||
| """ | ||
| private func withTransaction<T>(_ apply: () throws -> T) rethrows -> T { | ||
| _registrar.beginAccess() | ||
| defer { _registrar.endAccess() } | ||
| return try apply() | ||
| } | ||
| """ | ||
|
|
||
| let memberList = MemberDeclListSyntax( | ||
| declaration.members.members.filter { | ||
| $0.decl.isObservableStoredProperty | ||
| } | ||
| ) | ||
|
|
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| let storageStruct: DeclSyntax = | ||
| """ | ||
| private struct Storage { | ||
| \(memberList) | ||
| } | ||
| """ | ||
|
|
||
| let storage: DeclSyntax = | ||
| """ | ||
| private var _storage = Storage() | ||
| """ | ||
|
|
||
| return [ | ||
| registrar, | ||
| addObserver, | ||
| removeObserver, | ||
| withTransaction, | ||
| storageStruct, | ||
| storage, | ||
| ] | ||
| } | ||
|
|
||
| // MARK: - MemberAttributeMacro | ||
|
|
||
| public static func expansion( | ||
| of node: AttributeSyntax, | ||
| attachedTo declaration: some DeclGroupSyntax, | ||
| providingAttributesFor member: DeclSyntax, | ||
| in context: some MacroExpansionContext | ||
| ) throws -> [SwiftSyntax.AttributeSyntax] { | ||
| guard member.isObservableStoredProperty else { | ||
| return [] | ||
| } | ||
|
|
||
| return [ | ||
| AttributeSyntax( | ||
| attributeName: SimpleTypeIdentifierSyntax( | ||
| name: .identifier("ObservableProperty") | ||
| ) | ||
| ) | ||
| ] | ||
| } | ||
|
|
||
| } | ||
|
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| public struct ObservablePropertyMacro: AccessorMacro { | ||
| public static func expansion( | ||
| of node: AttributeSyntax, | ||
| providingAccessorsOf declaration: some DeclSyntaxProtocol, | ||
| in context: some MacroExpansionContext | ||
| ) throws -> [AccessorDeclSyntax] { | ||
| guard let property = declaration.as(VariableDeclSyntax.self), | ||
| let binding = property.bindings.first, | ||
| let identifier = binding.pattern.as(IdentifierPatternSyntax.self)?.identifier, | ||
| binding.accessor == nil | ||
| else { | ||
| return [] | ||
| } | ||
|
|
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| if identifier.text == "_registrar" || identifier.text == "_storage" { return [] } | ||
|
|
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| let getAccessor: AccessorDeclSyntax = | ||
| """ | ||
| get { | ||
| _registrar.beginAccess(\\.\(identifier)) | ||
| defer { _registrar.endAccess() } | ||
| return _storage.\(identifier) | ||
| } | ||
| """ | ||
|
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| let setAccessor: AccessorDeclSyntax = | ||
| """ | ||
| set { | ||
| _registrar.beginAccess(\\.\(identifier)) | ||
| _registrar.register(observable: self, willSet: \\.\(identifier), to: newValue) | ||
| defer { | ||
| _registrar.register(observable: self, didSet: \\.\(identifier)) | ||
| _registrar.endAccess() | ||
| } | ||
| _storage.\(identifier) = newValue | ||
| } | ||
| """ | ||
|
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| return [getAccessor, setAccessor] | ||
| } | ||
| } |