examples: add macros examples

Author: xinzhengzhang

examples/srcs/binary/swift_binaries/BUILD

@@ -8,6 +8,7 @@ swift_binary(
     ],
     deps = [
         "//srcs/shared/module_b:module_b",
+        "//srcs/shared/macros:stringify",
         "@swift_argument_parser//:ArgumentParser"
     ]
 )

examples/srcs/binary/swift_binaries/entrance.swift

@@ -1,6 +1,7 @@
 import Foundation
 import srcs_shared_module_b_module_b
 import ArgumentParser
+import Stringify
 
 @main
 struct Entrance: ParsableCommand {
@@ -10,5 +11,6 @@ struct Entrance: ParsableCommand {
     func run() throws {
         print(name)
         print(greeting_from_module_b())
+        print(#stringify(1 + 2))
     }
 }

examples/srcs/shared/macros/BUILD.bazel

@@ -0,0 +1,33 @@
+load("@build_bazel_rules_swift//swift:swift.bzl", "swift_binary", "swift_library", "swift_test")
+load("@build_bazel_rules_swift//swift:swift_compiler_plugin.bzl", "swift_compiler_plugin", "universal_swift_compiler_plugin")
+
+
+swift_library(
+    name = "stringify",
+    srcs = ["Stringify.swift"],
+    module_name = "Stringify",
+    plugins = [":stringify_macro"],
+    visibility = ["//visibility:public"],
+)
+
+swift_compiler_plugin(
+    name = "stringify_macro",
+    srcs = [
+        "StringifyMacro.swift",
+        "StringifyMacroPlugin.swift",
+    ],
+    module_name = "StringifyMacroPlugin",
+    deps = [
+        "@SwiftSyntax",
+        "@SwiftSyntax//:SwiftCompilerPlugin",
+        "@SwiftSyntax//:SwiftSyntaxBuilder",
+        "@SwiftSyntax//:SwiftSyntaxMacros",
+    ],
+)
+
+swift_binary(
+    name = "stringify_client",
+    srcs = ["StringifyClient.swift"],
+    deps = [":stringify"],
+)
+

examples/srcs/shared/macros/Stringify.swift

@@ -0,0 +1,17 @@
+// Copyright 2023 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+@freestanding(expression)
+public macro stringify<T>(_ value: T) -> (T, String) =
+  #externalMacro(module: "StringifyMacroPlugin", type: "StringifyMacro")

examples/srcs/shared/macros/StringifyClient.swift

@@ -0,0 +1,22 @@
+// Copyright 2023 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import Stringify
+
+@main
+struct Main {
+  static func main() {
+    print(#stringify(1 + 2))
+  }
+}

examples/srcs/shared/macros/StringifyMacro.swift

@@ -0,0 +1,29 @@
+// Copyright 2023 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import SwiftSyntaxMacros
+
+public struct StringifyMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    guard let argument = node.argumentList.first?.expression else {
+      fatalError("compiler bug: the macro does not have any arguments")
+    }
+    return "(\(argument), \(literal: argument.description))"
+  }
+}

examples/srcs/shared/macros/StringifyMacroPlugin.swift

@@ -0,0 +1,25 @@
+// Copyright 2023 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#if canImport(SwiftCompilerPlugin)
+import SwiftCompilerPlugin
+import SwiftSyntaxMacros
+
+@main
+struct StringifyMacroPlugin: CompilerPlugin {
+  let providingMacros: [Macro.Type] = [
+    StringifyMacro.self
+  ]
+}
+#endif