prepack: use dynamic imports instead of child process

explain ignoring of package specific prepack in `.eslintrc.js`

Author: Lms24

packages/gatsby/.eslintrc.js

@@ -6,6 +6,8 @@ module.exports = {
   parserOptions: {
     jsx: true,
   },
+  // ignoring the package-specific prepack script here b/c it is not
+  // covered by a `tsconfig` which makes eslint throw an error
   ignorePatterns: ['scripts/prepack.ts'],
   extends: ['../../.eslintrc.js'],
 };

packages/gatsby/scripts/prepack.ts

@@ -1,22 +1,26 @@
 /* eslint-disable no-console */
+
 // DO NOT RUN this script yourself!
 // This is invoked from the main `prepack.ts` script in `sentry-javascript/scripts/prepack.ts`.
+
 import * as fs from 'fs';
 import * as path from 'path';
 
-const BUILD_DIR = 'build';
 const PACKAGE_ASSETS = ['gatsby-browser.js', 'gatsby-node.js'];
 
-// copy package-specific assets to build dir
-PACKAGE_ASSETS.forEach(asset => {
-  const assetPath = path.resolve(asset);
-  try {
-    if (!fs.existsSync(assetPath)) {
-      console.error(`Asset ${asset} does not exist.`);
+export function prepack(buildDir: string): void {
+  // copy package-specific assets to build dir
+  PACKAGE_ASSETS.forEach(asset => {
+    const assetPath = path.resolve(asset);
+    try {
+      if (!fs.existsSync(assetPath)) {
+        console.error(`Asset ${asset} does not exist.`);
+        process.exit(1);
+      }
+      fs.copyFileSync(assetPath, path.resolve(buildDir, asset));
+    } catch (error) {
+      console.error(`Error while copying ${asset} to ${buildDir}`);
       process.exit(1);
     }
-    fs.copyFileSync(assetPath, path.resolve(BUILD_DIR, asset));
-  } catch (error) {
-    console.error(`Error while copying ${asset} to ${BUILD_DIR}`);
-  }
-});
+  });
+}

scripts/prepack.ts

@@ -6,7 +6,6 @@
   the directory structure inside `build`.
 */
 
-import * as childProcess from 'child_process';
 import * as fs from 'fs';
 import * as fse from 'fs-extra';
 import * as path from 'path';
@@ -89,19 +88,20 @@ try {
   process.exit(1);
 }
 
+async function runPackagePrepack(packagePrepackPath: string): Promise<void> {
+  const { prepack } = await import(packagePrepackPath);
+  if (prepack && typeof prepack === 'function') {
+    prepack(buildDir);
+  }
+}
+
 // execute package specific settings
 // 1. check if a package called `<package-root>/scripts/prepack.ts` exitsts
 // if yes, 2.) execute that script for things that are package-specific
 const packagePrepackPath = path.resolve('scripts', 'prepack.ts');
 try {
   if (fs.existsSync(packagePrepackPath)) {
-    const proc = childProcess.fork(packagePrepackPath);
-    proc.on('exit', code => {
-      if (code !== 0) {
-        console.error(`Error while executing ${packagePrepackPath.toString()}`);
-        process.exit(1);
-      }
-    });
+    void runPackagePrepack(packagePrepackPath);
   }
 } catch (error) {
   console.error(`Error while trying to access ${packagePrepackPath.toString()}`);