Make codegen generate a Package.swift file for Codegen'd target (facebook#53619)

Summary:
Pull Request resolved: facebook#53619

With this change, we are making Codegen generate a Package.swift file so that we can integrate the `ReactCodegen` and the `ReactAppDependencyProvider` in apps only using SwiftPM

## Changelog
[iOS][Added] - Make codegen generate PAckage.swift file for the codegen targets

Reviewed By: cortinico

Differential Revision: D81769543

fbshipit-source-id: 1f1a1b9f41126e142931d5eda6e75109a69f828c

Author: cipolleschi

packages/react-native/scripts/codegen/generate-artifacts-executor/generatePackageSwift.js

@@ -0,0 +1,44 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+'use strict';
+const {TEMPLATES_FOLDER_PATH} = require('./constants');
+const {codegenLog} = require('./utils');
+const fs = require('fs');
+const path = require('path');
+
+const PACKAGE_SWIFT_TEMPLATE_PATH = path.join(
+  TEMPLATES_FOLDER_PATH,
+  'Package.swift.template',
+);
+
+function generatePackageSwift(
+  projectRoot /*: string */,
+  outputDir /*: string */,
+  reactNativePath /*: string */,
+) {
+  const fullOutputPath = path.join(projectRoot, outputDir);
+  fs.mkdirSync(outputDir, {recursive: true});
+  // Generate PAckage.swift File
+  codegenLog('Generating Package.swift');
+  const templateH = fs
+    .readFileSync(PACKAGE_SWIFT_TEMPLATE_PATH, 'utf8')
+    .replace(
+      /{reactNativePath}/,
+      path.relative(fullOutputPath, reactNativePath),
+    );
+  const finalPathH = path.join(outputDir, 'Package.swift');
+  fs.writeFileSync(finalPathH, templateH);
+  codegenLog(`Generated artifact: ${finalPathH}`);
+}
+
+module.exports = {
+  generatePackageSwift,
+};

packages/react-native/scripts/codegen/generate-artifacts-executor/index.js

@@ -22,6 +22,7 @@ const {
 } = require('./generateAppDependencyProvider');
 const {generateCustomURLHandlers} = require('./generateCustomURLHandlers');
 const {generateNativeCode} = require('./generateNativeCode');
+const {generatePackageSwift} = require('./generatePackageSwift');
 const {generateRCTModuleProviders} = require('./generateRCTModuleProviders');
 const {
   generateRCTThirdPartyComponents,
@@ -37,6 +38,7 @@ const {
   codegenLog,
   findCodegenEnabledLibraries,
   findDisabledLibrariesByPlatform,
+  findReactNativeRootPath,
   pkgJsonIncludesGeneratedCode,
   readPkgJsonInDirectory,
   readReactNativeConfig,
@@ -160,6 +162,11 @@ function execute(
           reactCodegenOutputPath,
           baseOutputPath,
         );
+        generatePackageSwift(
+          projectRoot,
+          outputPath,
+          findReactNativeRootPath(projectRoot),
+        );
       }
 
       cleanupEmptyFilesAndFolders(outputPath);

packages/react-native/scripts/codegen/templates/Package.swift.template

@@ -0,0 +1,59 @@
+// swift-tools-version: 6.1
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "React-GeneratedCode",
+    platforms: [.iOS(.v15), .macCatalyst(SupportedPlatform.MacCatalystVersion.v13)],
+    products: [
+        // Products define the executables and libraries a package produces, making them visible to other packages.
+        .library(
+            name: "ReactCodegen",
+            targets: ["ReactCodegen"]),
+        .library(
+            name: "ReactAppDependencyProvider",
+            targets: ["ReactAppDependencyProvider"]),
+    ],
+    dependencies: [
+      .package(name: "React", path: "{reactNativePath}")
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package, defining a module or a test suite.
+        // Targets can depend on other targets in this package and products from dependencies.
+        .target(
+            name: "ReactCodegen",
+            dependencies: ["React"],
+            path: "ReactCodegen",
+            exclude: ["ReactCodegen.podspec"],
+            publicHeadersPath: ".",
+            cSettings: [
+              .headerSearchPath("headers")
+            ],
+            cxxSettings: [
+              .headerSearchPath("headers"),
+              .unsafeFlags(["-std=c++20"]),
+            ],
+            linkerSettings: [
+              .linkedFramework("Foundation")
+            ]
+        ),
+        .target(
+          name: "ReactAppDependencyProvider",
+          dependencies: ["ReactCodegen"],
+          path: "ReactAppDependencyProvider",
+          exclude: ["ReactAppDependencyProvider.podspec"],
+          publicHeadersPath: ".",
+          cSettings: [
+            .headerSearchPath("headers"),
+          ],
+          cxxSettings: [
+            .headerSearchPath("headers"),
+            .unsafeFlags(["-std=c++20"]),
+          ],
+          linkerSettings: [
+            .linkedFramework("Foundation")
+          ]
+        )
+    ]
+)