Add script to prepare the .build folder to prebuild React Native with SwiftPM (#51195)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51195

This change adds a script that prepares the repository by creating hard links to the header files in the `.build` folder that is also gitignored

## Changelog:
[Internal] - Add sdcript to setup the repository so that we can build it properly.

Test Plan:
run:
```
node packages/react-native/scripts/ios-prebuilds.js
```
observe the folder `.build` being created with all the files.

Reviewed By: cortinico

Differential Revision: D74393116

Pulled By: cipolleschi

fbshipit-source-id: 4951e61b49db83fbebbcc265ae025f53185fec81

.gitignore

@@ -124,6 +124,9 @@ vendor/
 !/packages/rn-tester/Pods/__offline_mirrors_hermes__
 !/packages/rn-tester/Pods/__offline_mirrors_jsc__
 
+# Swift Package build folder
+/packages/react-native/.build
+
 # @react-native/codegen
 /packages/react-native/React/FBReactNativeSpec/
 /packages/react-native-codegen/lib

packages/react-native/scripts/ios-prebuild.js

@@ -0,0 +1,165 @@
+/**
+ * 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
+ * @format
+ * @oncall react_native
+ */
+
+const {prepareHermesArtifactsAsync} = require('./ios-prebuild/hermes');
+const {
+  createFolderIfNotExists,
+  throwIfOnEden,
+} = require('./ios-prebuild/utils');
+const {execSync} = require('child_process');
+const fs = require('fs');
+const path = require('path');
+
+async function main() {
+  console.log('Prebuilding React Native iOS...');
+  console.log('');
+
+  throwIfOnEden();
+
+  try {
+    // Root
+    const root = process.cwd();
+
+    // Create build folder
+    const buildFolder = path.resolve(root, '.build');
+    createFolderIfNotExists(buildFolder);
+
+    // Create the hard links folder
+    const linksFolder = path.resolve(buildFolder, 'headers');
+    createFolderIfNotExists(linksFolder);
+
+    /**
+     * Creates a hard link from one path to another. For each subfolder
+     * in the source path, it creates a link in the target path with an
+     * underscore prefix.
+     * @param {string} fromPath - The path to the source file or directory
+     * @param {string} includePath - Path in the headers folder to create the link
+     * @throws {Error} If the source path does not exist or if the link creation fails
+     * @returns {void}
+     */
+    const link = (fromPath /*:string*/, includePath /*:string*/) => {
+      const source = path.resolve(root, fromPath);
+      const target = path.resolve(linksFolder, includePath);
+      console.log(`Linking ${source} to ${target}...`);
+
+      createFolderIfNotExists(target);
+
+      // get subfolders in source - make sure we only copy folders with header files
+      const entries = fs.readdirSync(source, {withFileTypes: true});
+      if (
+        entries.some(
+          dirent =>
+            dirent.isFile() &&
+            (String(dirent.name).endsWith('.h') ||
+              String(dirent.name).endsWith('.hpp')),
+        )
+      ) {
+        // Create link for all header files (*.h, *.hpp) in the source directory
+        entries.forEach(entry => {
+          const entryName = String(entry.name);
+          if (entry.isFile() && /\.(h|hpp)$/.test(entryName)) {
+            const sourceFile = path.join(source, entryName);
+            const targetFile = path.join(target, entryName);
+            // Skip if the file already exists
+            if (fs.existsSync(targetFile)) {
+              return;
+            }
+            try {
+              fs.linkSync(sourceFile, targetFile);
+            } catch (e) {
+              console.error(
+                `Failed to create link for ${sourceFile} to ${targetFile}: ${e}`,
+              );
+            }
+          }
+        });
+      }
+
+      const subfolders = entries
+        .filter(dirent => dirent.isDirectory())
+        .filter(dirent => dirent.name !== '__tests__')
+        .map(dirent => dirent.name);
+
+      // Create links for subfolders
+      subfolders.forEach(folder => {
+        link(path.join(fromPath, String(folder)), includePath);
+      });
+    };
+
+    // CODEGEN
+    console.log('Running codegen...');
+    const codegenPath = path.join(root, '.build/codegen');
+    createFolderIfNotExists(codegenPath);
+
+    const command = `node scripts/generate-codegen-artifacts -p "${root}" -o "${codegenPath}"  -t ios`;
+    console.log(command);
+    execSync(command, {stdio: 'inherit'});
+
+    // HERMES ARTIFACTS
+    console.log('Download hermes...');
+    // Temporary hardcoded hermes version to make the script work
+    // We will make it right in a future diff.
+    // TODO: T223708709
+    await prepareHermesArtifactsAsync('0.80.0-rc.0', 'release');
+
+    // LINKING
+    link('Libraries/WebSocket/', 'React');
+    link('React/Base', 'React');
+    link('React/Base/Surface', 'React');
+    link('React/CxxBridge', 'React');
+    link('React/CxxModule', 'React');
+    link('React/CxxUtils', 'React');
+    link('React/DevSupport', 'React');
+    link('React/Inspector', 'React');
+    link('React/I18n', 'React');
+    link('React/Views', 'React');
+    link('React/CoreModules', 'React');
+    link('React/Modules', 'React');
+    link('React/Fabric', 'React');
+    link('React/Profiler', 'React');
+    link('React/CoreModules', 'React');
+    link('React/Runtime', 'React');
+    link('React/Views/ScrollView', 'React');
+    link('React/Views/RefreshControl', 'React');
+    link('Libraries/Text', 'React');
+    link(
+      'ReactApple/Libraries/RCTFoundation/RCTDeprecation/Exported',
+      'RCTDeprecation',
+    );
+    link('Libraries/Required', 'RCTRequired');
+    link('Libraries/TypeSafety', 'RCTTypeSafety');
+    link('Libraries/Text', 'React');
+    link('Libraries/Image', 'React');
+    link('Libraries/Network', 'React');
+    link('Libraries/Blob', 'React');
+    link('Libraries/NativeAnimation', 'React');
+    link('Libraries/LinkingIOS', 'React');
+
+    link('ReactCommon/hermes', 'reacthermes');
+    link('ReactCommon/hermes', 'jsireact');
+
+    link(
+      'ReactCommon/react/renderer/imagemanager',
+      'react/renderer/imagemanager',
+    );
+
+    // Done!
+    console.log('🏁 Done!');
+  } catch (err) {
+    console.error(err);
+    process.exitCode = 1;
+  }
+}
+
+if (require.main === module) {
+  // eslint-disable-next-line no-void
+  void main();
+}

packages/react-native/scripts/ios-prebuild/utils.js

@@ -9,6 +9,7 @@
  * @oncall react_native
  */
 
+const {execSync} = require('child_process');
 const fs = require('fs');
 
 /**
@@ -26,4 +27,18 @@ function createFolderIfNotExists(folderPath /*:string*/) /*: string*/ {
   return folderPath;
 }
 
-module.exports = {createFolderIfNotExists};
+function throwIfOnEden() {
+  try {
+    execSync('eden info');
+  } catch (error) {
+    // eden info failed, we are not on Eden, do nothing
+    return;
+  }
+
+  throw new Error('Cannot prepare the iOS prebuilds on an Eden checkout');
+}
+
+module.exports = {
+  createFolderIfNotExists,
+  throwIfOnEden,
+};