Align default transform profile Babel preset with legacy Hermes - drop "older" engines (#54806)

robhogan · facebook-github-bot · commit 7b38928c21ce · 2025-12-12T07:54:35.000-08:00
Summary:

Align the default transform profile in our Babel preset with the current state of `hermes-stable`, drop non-Hermes, pre-ES6 engines which have been unsupported in core since the JSC removal.

This will allow us to subsequently repurpose transform profiles (`unstable_transformProfile`) to remove transforms unnecessary for Hermes v1 (aka Static Hermes) as follows:

- `hermes-canary` -&gt; Hermes v1 (experimental features)
- `hermes-stable` -&gt; Hermes v1
- Default -&gt; All supported engines (i.e, Hermes v1 and legacy)

Changelog:

[General][Removed] Remove Babel preset transforms for already-unsupported non-Hermes engines

Reviewed By: javache, huntie

Differential Revision: D88269506
diff --git a/packages/react-native-babel-preset/package.json b/packages/react-native-babel-preset/package.json
@@ -31,27 +31,19 @@
     "@babel/plugin-syntax-export-default-from": "^7.24.7",
     "@babel/plugin-syntax-nullish-coalescing-operator": "^7.8.3",
     "@babel/plugin-syntax-optional-chaining": "^7.8.3",
-    "@babel/plugin-transform-arrow-functions": "^7.24.7",
     "@babel/plugin-transform-async-generator-functions": "^7.25.4",
     "@babel/plugin-transform-async-to-generator": "^7.24.7",
     "@babel/plugin-transform-block-scoping": "^7.25.0",
     "@babel/plugin-transform-class-properties": "^7.25.4",
     "@babel/plugin-transform-classes": "^7.25.4",
-    "@babel/plugin-transform-computed-properties": "^7.24.7",
     "@babel/plugin-transform-destructuring": "^7.24.8",
     "@babel/plugin-transform-flow-strip-types": "^7.25.2",
     "@babel/plugin-transform-for-of": "^7.24.7",
-    "@babel/plugin-transform-function-name": "^7.25.1",
-    "@babel/plugin-transform-literals": "^7.25.2",
-    "@babel/plugin-transform-logical-assignment-operators": "^7.24.7",
     "@babel/plugin-transform-modules-commonjs": "^7.24.8",
     "@babel/plugin-transform-named-capturing-groups-regex": "^7.24.7",
     "@babel/plugin-transform-nullish-coalescing-operator": "^7.24.7",
-    "@babel/plugin-transform-numeric-separator": "^7.24.7",
-    "@babel/plugin-transform-object-rest-spread": "^7.24.7",
     "@babel/plugin-transform-optional-catch-binding": "^7.24.7",
     "@babel/plugin-transform-optional-chaining": "^7.24.8",
-    "@babel/plugin-transform-parameters": "^7.24.7",
     "@babel/plugin-transform-private-methods": "^7.24.7",
     "@babel/plugin-transform-private-property-in-object": "^7.24.7",
     "@babel/plugin-transform-react-display-name": "^7.24.7",
@@ -60,12 +52,8 @@
     "@babel/plugin-transform-react-jsx-source": "^7.24.7",
     "@babel/plugin-transform-regenerator": "^7.24.7",
     "@babel/plugin-transform-runtime": "^7.24.7",
-    "@babel/plugin-transform-shorthand-properties": "^7.24.7",
-    "@babel/plugin-transform-spread": "^7.24.7",
-    "@babel/plugin-transform-sticky-regex": "^7.24.7",
     "@babel/plugin-transform-typescript": "^7.25.2",
     "@babel/plugin-transform-unicode-regex": "^7.24.7",
-    "@babel/template": "^7.25.0",
     "@react-native/babel-plugin-codegen": "0.84.0-main",
     "babel-plugin-syntax-hermes-parser": "0.32.0",
     "babel-plugin-transform-flow-enums": "^0.0.2",
diff --git a/packages/react-native-babel-preset/src/configs/main.js b/packages/react-native-babel-preset/src/configs/main.js
@@ -49,13 +49,15 @@ const getPreset = (src, options) => {
   const isHermesCanary = transformProfile === 'hermes-canary';
   const isHermes = isHermesStable || isHermesCanary;
 
-  // We enable regenerator for !isHermes. Additionally, in dev mode we also
-  // enable regenerator for the time being because Static Hermes doesn't yet
-  // support debugging native generators. However, some apps have native
-  // generators in release mode because it has already yielded perf wins. The
-  // next release of Static Hermes will close this gap, so this won't be
-  // permanent.
-  const enableRegenerator = !isHermes || options.dev;
+  // We enable regenerator in dev builds for the time being because
+  // Static Hermes doesn't yet fully support debugging native generators.
+  // (e.g. - it's not possible to inspect local variables when paused in a
+  // generator).
+  //
+  // Use native generators in release mode because it has already yielded perf
+  // wins. The next release of Static Hermes will close this gap, so this won't
+  // be permanent.
+  const enableRegenerator = isHermes && options.dev;
 
   const isNull = src == null;
   const hasClass = isNull || src.indexOf('class') !== -1;
@@ -102,48 +104,20 @@ const getPreset = (src, options) => {
     extraPlugins.push([require('@babel/plugin-transform-classes')]);
   }
 
-  if (!isHermes && (isNull || src.includes('=>'))) {
-    extraPlugins.push([require('@babel/plugin-transform-arrow-functions')]);
-  }
-
-  if (!isHermes) {
-    extraPlugins.push([require('@babel/plugin-transform-computed-properties')]);
-    extraPlugins.push([require('@babel/plugin-transform-parameters')]);
-    extraPlugins.push([
-      require('@babel/plugin-transform-shorthand-properties'),
-    ]);
+  extraPlugins.push([
+    require('@babel/plugin-transform-named-capturing-groups-regex'),
+  ]);
+  // Needed for regenerator
+  if (enableRegenerator) {
     extraPlugins.push([
       require('@babel/plugin-transform-optional-catch-binding'),
     ]);
-    extraPlugins.push([require('@babel/plugin-transform-function-name')]);
-    extraPlugins.push([require('@babel/plugin-transform-literals')]);
-    extraPlugins.push([require('@babel/plugin-transform-numeric-separator')]);
-    extraPlugins.push([require('@babel/plugin-transform-sticky-regex')]);
-  } else {
-    extraPlugins.push([
-      require('@babel/plugin-transform-named-capturing-groups-regex'),
-    ]);
-    // Needed for regenerator
-    if (isHermes && enableRegenerator) {
-      extraPlugins.push([
-        require('@babel/plugin-transform-optional-catch-binding'),
-      ]);
-    }
   }
+
   extraPlugins.push([
     require('@babel/plugin-transform-destructuring'),
     {useBuiltIns: true},
   ]);
-  if (!isHermes && (isNull || hasClass || src.indexOf('...') !== -1)) {
-    extraPlugins.push(
-      [require('@babel/plugin-transform-spread')],
-      [
-        require('@babel/plugin-transform-object-rest-spread'),
-        // Assume no dependence on getters or evaluation order. See https://github.com/babel/babel/pull/11520
-        {loose: true, useBuiltIns: true},
-      ],
-    );
-  }
   if (isNull || src.indexOf('async') !== -1) {
     extraPlugins.push([
       require('@babel/plugin-transform-async-generator-functions'),
@@ -171,18 +145,6 @@ const getPreset = (src, options) => {
       {loose: true},
     ]);
   }
-  if (
-    !isHermes &&
-    (isNull ||
-      src.indexOf('??=') !== -1 ||
-      src.indexOf('||=') !== -1 ||
-      src.indexOf('&&=') !== -1)
-  ) {
-    extraPlugins.push([
-      require('@babel/plugin-transform-logical-assignment-operators'),
-      {loose: true},
-    ]);
-  }
 
   if (options && options.dev && !options.disableDeepImportWarnings) {
     firstPartyPlugins.push([require('../plugin-warn-on-deep-imports.js')]);
@@ -193,16 +155,15 @@ const getPreset = (src, options) => {
     extraPlugins.push([require('@babel/plugin-transform-react-jsx-self')]);
   }
 
-  if (isHermes && enableRegenerator) {
-    const hasForOf =
-      isNull || (src.indexOf('for') !== -1 && src.indexOf('of') !== -1);
-    if (hasForOf) {
-      // Needed for regenerator
-      extraPlugins.push([
-        require('@babel/plugin-transform-for-of'),
-        {loose: true},
-      ]);
-    }
+  if (
+    enableRegenerator &&
+    (isNull || (src.indexOf('for') !== -1 && src.indexOf('of') !== -1))
+  ) {
+    // Needed for regenerator
+    extraPlugins.push([
+      require('@babel/plugin-transform-for-of'),
+      {loose: true},
+    ]);
   }
 
   if (!options || options.enableBabelRuntime !== false) {
@@ -217,7 +178,7 @@ const getPreset = (src, options) => {
         ...(isVersion && {version: options.enableBabelRuntime}),
       },
     ]);
-  } else if (isHermes && enableRegenerator) {
+  } else if (enableRegenerator) {
     extraPlugins.push([require('@babel/plugin-transform-regenerator')]);
   }
 
diff --git a/packages/react-native/Libraries/StyleSheet/__tests__/__snapshots__/processAspectRatio-test.js.snap b/packages/react-native/Libraries/StyleSheet/__tests__/__snapshots__/processAspectRatio-test.js.snap
@@ -6,7 +6,7 @@ exports[`processAspectRatio should not accept invalid formats 2`] = `"aspectRati
 
 exports[`processAspectRatio should not accept invalid formats 3`] = `"aspectRatio must either be a number, a ratio string or \`auto\`. You passed: auto 1/1"`;
 
-exports[`processAspectRatio should not accept non string truthy types 1`] = `"aspectRatio must either be a number, a ratio string or \`auto\`. You passed: function () {}"`;
+exports[`processAspectRatio should not accept non string truthy types 1`] = `"aspectRatio must either be a number, a ratio string or \`auto\`. You passed: () => {}"`;
 
 exports[`processAspectRatio should not accept non string truthy types 2`] = `"aspectRatio must either be a number, a ratio string or \`auto\`. You passed: 1,2,3"`;
 
diff --git a/packages/react-native/jest/mockComponent.js b/packages/react-native/jest/mockComponent.js
@@ -39,7 +39,7 @@ export default function mockComponent<
 
   const SuperClass: typeof React.Component<{...}> =
     typeof RealComponent === 'function' &&
-    RealComponent.prototype.constructor instanceof React.Component
+    RealComponent.prototype?.constructor instanceof React.Component
       ? RealComponent
       : React.Component;
 
diff --git a/yarn.lock b/yarn.lock
@@ -462,7 +462,7 @@
     "@babel/helper-create-regexp-features-plugin" "^7.18.6"
     "@babel/helper-plugin-utils" "^7.18.6"
 
-"@babel/plugin-transform-arrow-functions@^7.24.7", "@babel/plugin-transform-arrow-functions@^7.25.9":
+"@babel/plugin-transform-arrow-functions@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-arrow-functions/-/plugin-transform-arrow-functions-7.25.9.tgz#7821d4410bee5daaadbb4cdd9a6649704e176845"
   integrity sha512-6jmooXYIwn9ca5/RylZADJ+EnSxVUS5sjeJ9UPk6RWRzXCmOJCy6dqItPJFpw2cuCangPK4OYr5uhGKcmrm5Qg==
@@ -529,7 +529,7 @@
     "@babel/traverse" "^7.25.9"
     globals "^11.1.0"
 
-"@babel/plugin-transform-computed-properties@^7.24.7", "@babel/plugin-transform-computed-properties@^7.25.9":
+"@babel/plugin-transform-computed-properties@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-computed-properties/-/plugin-transform-computed-properties-7.25.9.tgz#db36492c78460e534b8852b1d5befe3c923ef10b"
   integrity sha512-HnBegGqXZR12xbcTHlJ9HGxw1OniltT26J5YpfruGqtUHlz/xKf/G2ak9e+t0rVqrjXa9WOhvYPz1ERfMj23AA==
@@ -604,7 +604,7 @@
     "@babel/helper-plugin-utils" "^7.26.5"
     "@babel/helper-skip-transparent-expression-wrappers" "^7.25.9"
 
-"@babel/plugin-transform-function-name@^7.25.1", "@babel/plugin-transform-function-name@^7.25.9":
+"@babel/plugin-transform-function-name@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-function-name/-/plugin-transform-function-name-7.25.9.tgz#939d956e68a606661005bfd550c4fc2ef95f7b97"
   integrity sha512-8lP+Yxjv14Vc5MuWBpJsoUCd3hD6V9DgBon2FVYL4jJgbnVQ9fTgYmonchzZJOVNgzEgbxp4OwAf6xz6M/14XA==
@@ -620,14 +620,14 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.25.9"
 
-"@babel/plugin-transform-literals@^7.25.2", "@babel/plugin-transform-literals@^7.25.9":
+"@babel/plugin-transform-literals@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-literals/-/plugin-transform-literals-7.25.9.tgz#1a1c6b4d4aa59bc4cad5b6b3a223a0abd685c9de"
   integrity sha512-9N7+2lFziW8W9pBl2TzaNht3+pgMIRP74zizeCSrtnSKVdUl8mAjjOP2OOVQAfZ881P2cNjDj1uAMEdeD50nuQ==
   dependencies:
     "@babel/helper-plugin-utils" "^7.25.9"
 
-"@babel/plugin-transform-logical-assignment-operators@^7.24.7", "@babel/plugin-transform-logical-assignment-operators@^7.25.9":
+"@babel/plugin-transform-logical-assignment-operators@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-logical-assignment-operators/-/plugin-transform-logical-assignment-operators-7.25.9.tgz#b19441a8c39a2fda0902900b306ea05ae1055db7"
   integrity sha512-wI4wRAzGko551Y8eVf6iOY9EouIDTtPb0ByZx+ktDGHwv6bHFimrgJM/2T021txPZ2s4c7bqvHbd+vXG6K948Q==
@@ -697,7 +697,7 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.26.5"
 
-"@babel/plugin-transform-numeric-separator@^7.24.7", "@babel/plugin-transform-numeric-separator@^7.25.9":
+"@babel/plugin-transform-numeric-separator@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-numeric-separator/-/plugin-transform-numeric-separator-7.25.9.tgz#bfed75866261a8b643468b0ccfd275f2033214a1"
   integrity sha512-TlprrJ1GBZ3r6s96Yq8gEQv82s8/5HnCVHtEJScUj90thHQbwe+E5MLhi2bbNHBEJuzrvltXSru+BUxHDoog7Q==
@@ -736,7 +736,7 @@
     "@babel/helper-plugin-utils" "^7.25.9"
     "@babel/helper-skip-transparent-expression-wrappers" "^7.25.9"
 
-"@babel/plugin-transform-parameters@^7.24.7", "@babel/plugin-transform-parameters@^7.25.9":
+"@babel/plugin-transform-parameters@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-parameters/-/plugin-transform-parameters-7.25.9.tgz#b856842205b3e77e18b7a7a1b94958069c7ba257"
   integrity sha512-wzz6MKwpnshBAiRmn4jR8LYz/g8Ksg0o80XmwZDlordjwEk9SxBzTWC7F5ef1jhbrbOW2DJ5J6ayRukrJmnr0g==
@@ -834,22 +834,22 @@
     babel-plugin-polyfill-regenerator "^0.6.1"
     semver "^6.3.1"
 
-"@babel/plugin-transform-shorthand-properties@^7.24.7", "@babel/plugin-transform-shorthand-properties@^7.25.9":
+"@babel/plugin-transform-shorthand-properties@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-shorthand-properties/-/plugin-transform-shorthand-properties-7.25.9.tgz#bb785e6091f99f826a95f9894fc16fde61c163f2"
   integrity sha512-MUv6t0FhO5qHnS/W8XCbHmiRWOphNufpE1IVxhK5kuN3Td9FT1x4rx4K42s3RYdMXCXpfWkGSbCSd0Z64xA7Ng==
   dependencies:
     "@babel/helper-plugin-utils" "^7.25.9"
 
-"@babel/plugin-transform-spread@^7.24.7", "@babel/plugin-transform-spread@^7.25.9":
+"@babel/plugin-transform-spread@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-spread/-/plugin-transform-spread-7.25.9.tgz#24a35153931b4ba3d13cec4a7748c21ab5514ef9"
   integrity sha512-oNknIB0TbURU5pqJFVbOOFspVlrpVwo2H1+HUIsVDvp5VauGGDP1ZEvO8Nn5xyMEs3dakajOxlmkNW7kNgSm6A==
   dependencies:
     "@babel/helper-plugin-utils" "^7.25.9"
     "@babel/helper-skip-transparent-expression-wrappers" "^7.25.9"
 
-"@babel/plugin-transform-sticky-regex@^7.24.7", "@babel/plugin-transform-sticky-regex@^7.25.9":
+"@babel/plugin-transform-sticky-regex@^7.25.9":
   version "7.25.9"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-sticky-regex/-/plugin-transform-sticky-regex-7.25.9.tgz#c7f02b944e986a417817b20ba2c504dfc1453d32"
   integrity sha512-WqBUSgeVwucYDP9U/xNRQam7xV8W5Zf+6Eo7T2SRVUFlhRiMNFdFz58u0KZmCVVqs2i7SHgpRnAhzRNmKfi2uA==
