1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
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: some DeclSyntaxProtocol,
in context: Context
) throws -> [AttributeSyntax] {
guard let property = member.as(VariableDeclSyntax.self),
property.isStoredProperty
else {
return []
}
guard case let .argumentList(arguments) = node.arguments,
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(
leadingTrivia: [.newlines(1), .spaces(2)],
attributeName: IdentifierTypeSyntax(
name: .identifier(wrapperName.content.text)
)
)
]
}
}
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
}
let binding = bindings.first!
switch binding.accessorBlock?.accessors {
case .none:
return true
case .accessors(let accessors):
for accessor in accessors {
switch accessor.accessorSpecifier.tokenKind {
case .keyword(.willSet), .keyword(.didSet):
// Observers can occur on a stored property.
break
default:
// Other accessors make it a computed property.
return false
}
}
return true
case .getter:
return false
}
}
}
extension DeclGroupSyntax {
/// Enumerate the stored properties that syntactically occur in this
/// declaration.
func storedProperties() -> [VariableDeclSyntax] {
return memberBlock.members.compactMap { member in
guard let variable = member.decl.as(VariableDeclSyntax.self),
variable.isStoredProperty
else {
return nil
}
return variable
}
}
}
|
