Breaking: Use named exports in metro-babel-register (#52564 )

Summary: Currently, `metro-babel-register` has a function as its default export, to which we've tagged on various properties. This tidies that up to a more idiomatic object of named exports, with `register` as a new one of them. This also serves to make it more compatible with automatic TypeScript generation. This is semver breaking, but `metro-babel-register` has very little usage outside Meta projects so isn't expected to be disruptive. Changelog: [Internal] Metro changelog: ``` - **[Breaking]**: Move metro-babel-register's main function to a named export `register` ``` Differential Revision: D78157559
Remove HTTP keepAliveTimeout workaround not needed since Node.js 12 (#52561 )
2025-11-01 09:14:26 +00:00 · 2025-07-11 05:18:58 -07:00 · 2025-07-11 05:18:58 -07:00
2 changed files with 10 additions and 14 deletions
@@ -147,7 +147,7 @@ async function runServer(
  // $FlowIgnore[cannot-write] Assigning to readonly property
  metroConfig.reporter = reporter;

-  const serverInstance = await Metro.runServer(metroConfig, {
+  await Metro.runServer(metroConfig, {
    host: args.host,
    secure: args.https,
    secureCert: args.cert,
@@ -161,18 +161,6 @@ async function runServer(

  reportEvent = eventsSocketEndpoint.reportEvent;

-  // In Node 8, the default keep-alive for an HTTP connection is 5 seconds. In
-  // early versions of Node 8, this was implemented in a buggy way which caused
-  // some HTTP responses (like those containing large JS bundles) to be
-  // terminated early.
-  //
-  // As a workaround, arbitrarily increase the keep-alive from 5 to 30 seconds,
-  // which should be enough to send even the largest of JS bundles.
-  //
-  // For more info: https://github.com/nodejs/node/issues/13391
-  //
-  serverInstance.keepAliveTimeout = 30000;
-
  await version.logIfUpdateAvailable(cliConfig, terminalReporter);
 }

@@ -41,7 +41,15 @@ function registerForMonorepo() {
    // $FlowExpectedError[cannot-resolve-module] - Won't resolve in OSS
    require('@fb-tools/babel-register');
  } else {
-    require('metro-babel-register')([
+    // Temporarily allow the default export to be a function (Metro <= 0.82),
+    // or contain a `register` function (Metro >= 0.83). Remove shim once Metro
+    // is bumped in OSS.
+    const metroBabelRegister = require('metro-babel-register') /*:: as $FlowFixMe */;
+    const registerFunction =
+      typeof metroBabelRegister.register === 'function'
+        ? metroBabelRegister.register
+        : metroBabelRegister;
+    registerFunction([
      PACKAGES_DIR,
      PRIVATE_DIR,
      SCRIPTS_DIR,