handle polyfills when building

Author: lobsterkatie

packages/utils/package.json

@@ -28,7 +28,7 @@
     "build:dev": "run-s build",
     "build:es5": "yarn build:cjs # *** backwards compatibility - remove in v7 ***",
     "build:esm": "tsc -p tsconfig.esm.json",
-    "build:rollup": "rollup -c rollup.npm.config.js",
+    "build:rollup": "yarn ts-node scripts/buildRollup.ts",
     "build:types": "tsc -p tsconfig.types.json",
     "build:watch": "run-p build:cjs:watch build:esm:watch build:types:watch",
     "build:cjs:watch": "tsc -p tsconfig.cjs.json --watch",

packages/utils/rollup.npm.config.js

@@ -1,3 +1,9 @@
 import { makeBaseNPMConfig, makeNPMConfigVariants } from '../../rollup/index.js';
 
-export default makeNPMConfigVariants(makeBaseNPMConfig());
+export default makeNPMConfigVariants(
+  makeBaseNPMConfig({
+    // We build the polyfills separately because they're not included in the top-level exports of the package, in order
+    // to keep them out of the public API.
+    entrypoints: ['src/index.ts', 'src/buildPolyfills/index.ts'],
+  }),
+);

packages/utils/scripts/buildRollup.ts

@@ -0,0 +1,22 @@
+import * as childProcess from 'child_process';
+import * as fs from 'fs';
+
+/**
+ * Run the given shell command, piping the shell process's `stdin`, `stdout`, and `stderr` to that of the current
+ * process. Returns contents of `stdout`.
+ */
+function run(cmd: string, options?: childProcess.ExecSyncOptions): string | Buffer {
+  return childProcess.execSync(cmd, { stdio: 'inherit', ...options });
+}
+
+run('yarn rollup -c rollup.npm.config.js');
+
+// We want to distribute the README because it contains the MIT license blurb from Sucrase and Rollup
+fs.copyFileSync('src/buildPolyfills/README.md', 'build/cjs/buildPolyfills/README.md');
+fs.copyFileSync('src/buildPolyfills/README.md', 'build/esm/buildPolyfills/README.md');
+
+// Because we import our polyfills from `@sentry/utils/cjs/buildPolyfills` and `@sentry/utils/esm/buildPolyfills` rather
+// than straight from `@sentry/utils` (so as to avoid having them in the package's public API), when tests run, they'll
+// expect to find `cjs` and `esm` at the root level of the repo.
+fs.symlinkSync('build/cjs', 'cjs');
+fs.symlinkSync('build/esm', 'esm');