Support StorybookPreview macro in Preview declarations

Development/Demo/MyBook.swift

@@ -190,6 +190,25 @@ let myBook = Book.init(
   }
 }
 
+
+#Preview("Some title") {
+  #StorybookPreview<UILabel> {
+    BookPreview { _ in
+      let label = UILabel()
+      label.text = "UILabel 1"
+      return label
+    }
+  }
+}
+
+#Preview("Some title 2") {
+  #StorybookPreview<MyLabel> {
+    BookPreview { _ in
+      MyLabel(title: "MyLabel 2")
+    }
+  }
+}
+
 #StorybookPage<MyLabel> {
   BookPreview { _ in
     MyLabel(title: "Test")

Sources/StorybookKit/StorybookKit.swift

@@ -40,3 +40,21 @@ public macro StorybookPage<Target>(
   module: "StorybookMacrosPlugin",
   type: "StorybookPageMacro"
 )
+
+@freestanding(expression)
+public macro StorybookPreview(
+  title: String,
+  @ViewBuilder contents: @escaping () -> any View
+) -> AnyView = #externalMacro(
+  module: "StorybookMacrosPlugin",
+  type: "StorybookPreviewMacro"
+)
+
+@freestanding(expression)
+public macro StorybookPreview<Target>(
+  target: Target.Type = Target.self,
+  @ViewBuilder contents: @escaping () -> any View
+) -> AnyView = #externalMacro(
+  module: "StorybookMacrosPlugin",
+  type: "StorybookPreviewMacro"
+)

Sources/StorybookMacrosPlugin/StorybookMacrosPlugin.swift

@@ -30,6 +30,7 @@ struct StorybookMacrosPlugin: CompilerPlugin {
   // MARK: CompilerPlugin
 
   let providingMacros: [Macro.Type] = [
-    StorybookPageMacro.self
+    StorybookPageMacro.self,
+    StorybookPreviewMacro.self
   ]
 }

Sources/StorybookMacrosPlugin/StorybookPageMacro.swift

@@ -58,9 +58,11 @@ public struct StorybookPageMacro: DeclarationMacro {
         """
       )
     ]
-
   }
 
+
+  // MARK: Private
+
   private static func parseArguments(
     from node: some FreestandingMacroExpansionSyntax
   ) throws -> (

Sources/StorybookMacrosPlugin/StorybookPreviewMacro.swift

@@ -0,0 +1,106 @@
+//
+// Copyright (c) 2024 Eureka, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+import Foundation
+import SwiftCompilerPlugin
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import SwiftSyntaxMacros
+
+// MARK: - StorybookPreviewMacro
+
+public struct StorybookPreviewMacro: ExpressionMacro {
+
+  // MARK: Internal
+
+  /// Should match `Book._magicSubstring`
+  static let _magicSubstring: String = "__🤖🛠️_StorybookMagic_"
+
+  // MARK: ExpressionMacro
+
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) throws -> ExprSyntax {
+    let (title, closure) = try self.parseArguments(from: node)
+    let enumName = context.makeUniqueName(
+      self._magicSubstring
+    )
+    return .init(
+      stringLiteral: """
+      {
+        enum \(enumName): BookProvider {
+          static var bookBody: BookPage {
+            .init(
+              title: \(title),
+              destination: \(closure)
+            )
+          }
+        }
+        return \(enumName).bookBody.destination
+      }()
+      """
+    )
+  }
+
+
+  // MARK: Private
+
+  private static func parseArguments(
+    from node: some FreestandingMacroExpansionSyntax
+  ) throws -> (
+    title: ExprSyntax,
+    closure: ClosureExprSyntax
+  ) {
+    var argumentsIterator = node.argumentList.makeIterator()
+    var title: ExprSyntax? = (node.genericArgumentClause?.arguments.first?.argument)
+      .flatMap { genericType -> TypeSyntaxProtocol? in
+        genericType.as(IdentifierTypeSyntax.self)
+        ?? genericType.as(MemberTypeSyntax.self)
+      }
+      .map({ .init(stringLiteral: "_typeName(\($0).self)") })
+
+    var closure: ClosureExprSyntax? = node.trailingClosure
+    while let argument = argumentsIterator.next()?
+      .as(LabeledExprSyntax.self) {
+
+      switch argument.label?.text {
+
+      case "title"?:
+        title = argument.expression
+
+      case "target"?:
+        title = .init(stringLiteral: "_typeName(\(argument))")
+
+      case "contents"?:
+        closure = argument.expression
+          .as(ClosureExprSyntax.self)
+
+      default:
+        fatalError()
+      }
+    }
+    return (
+      title: title!,
+      closure: closure!
+    )
+  }
+}