[breaking] Use Babel 8 (#257)

Author: nicolo-ribaudo

.github/workflows/ci.yml

@@ -76,6 +76,43 @@ jobs:
       - name: Test the esm build
         run: yarn test:esm
 
+  test-babel7:
+    name: Test with Babel 7
+    needs: prepare-yarn-cache
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+      - name: Use Node.js latest
+        uses: actions/setup-node@v3
+        with:
+          cache: "yarn"
+      - name: Install
+        run: yarn install
+      - name: Build
+        run: yarn build
+        env:
+          BABEL_ENV: production
+      - name: Downgrade to Babel 7
+        run: |
+          node scripts/downgrade-babel-to-v7.mjs
+          YARN_ENABLE_IMMUTABLE_INSTALLS=false yarn install
+      - name: Delete tests that import .ts files
+        run: rm packages/babel-helper-define-polyfill-provider/test/meta-resolver.js packages/babel-plugin-polyfill-corejs3/test/check-builtin-definitions.test.js
+      - name: Remove Babel 8-specific fixtures
+        run: |
+          # These fixtures produce different output with Babel 7 due to
+          # behavioral changes in @babel/helper-compilation-targets and
+          # @babel/plugin-transform-classes between Babel 7 and 8.
+          rm -rf packages/babel-plugin-polyfill-corejs3/test/fixtures/regression/usage-pure-in-helpers
+          rm -rf packages/babel-plugin-polyfill-corejs3/test/fixtures/usage-global/browserslist-config-ignore
+          rm -rf packages/babel-plugin-polyfill-corejs3/test/fixtures/usage-global/dynamic-import
+          rm -rf packages/babel-plugin-polyfill-corejs3/test/fixtures/usage-global/dynamic-import-webpack
+      - name: Test
+        run: yarn jest --ci --color --maxWorkers=2
+      - name: Test the esm build
+        run: yarn test:esm
+
   test-windows:
     name: Test on Windows
     needs: prepare-yarn-cache

babel.config.json

@@ -1,7 +1,7 @@
 {
   "sourceType": "unambiguous",
   "presets": [
-    ["@babel/preset-env", { "loose": true }],
+    "@babel/preset-env",
     "@babel/preset-typescript"
   ],
   "plugins": ["./scripts/babel-plugin-compat-core-import"],

package.json

@@ -18,14 +18,14 @@
     "watch": "gulp watch"
   },
   "devDependencies": {
-    "@babel/cli": "^7.28.6",
-    "@babel/core": "^7.28.6",
-    "@babel/eslint-parser": "^7.28.6",
-    "@babel/eslint-plugin-development": "^7.28.6",
-    "@babel/plugin-transform-runtime": "^7.28.5",
-    "@babel/preset-env": "^7.28.6",
-    "@babel/preset-typescript": "^7.28.5",
-    "@babel/runtime": "^7.28.6",
+    "@babel/cli": "^8.0.0-rc.3 <8.0.0",
+    "@babel/core": "^8.0.0-rc.3 <8.0.0",
+    "@babel/eslint-parser": "^8.0.0-rc.3 <8.0.0",
+    "@babel/eslint-plugin-development": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-runtime": "^8.0.0-rc.3 <8.0.0",
+    "@babel/preset-env": "^8.0.0-rc.3 <8.0.0",
+    "@babel/preset-typescript": "^8.0.0-rc.3 <8.0.0",
+    "@babel/runtime": "^8.0.0-rc.3 <8.0.0",
     "@rollup/plugin-babel": "^7.0.0",
     "@rollup/plugin-json": "^6.1.0",
     "@rollup/plugin-node-resolve": "^16.0.3",

packages/babel-helper-define-polyfill-provider/package.json

@@ -26,19 +26,19 @@
     "./package.json": "./package.json"
   },
   "dependencies": {
-    "@babel/helper-compilation-targets": "^7.28.6",
-    "@babel/helper-plugin-utils": "^7.28.6",
+    "@babel/helper-compilation-targets": "^8.0.0-rc.3 <8.0.0",
+    "@babel/helper-plugin-utils": "^8.0.0-rc.3 <8.0.0",
     "lodash.debounce": "^4.0.8"
   },
   "peerDependencies": {
-    "@babel/core": "^7.4.0 || ^8.0.0-0 <8.0.0"
+    "@babel/core": "^7.4.0 || ^8.0.0-rc.3"
   },
   "devDependencies": {
-    "@babel/cli": "^7.28.6",
-    "@babel/core": "^7.28.6",
-    "@babel/generator": "^7.28.6",
-    "@babel/plugin-transform-modules-commonjs": "^7.28.6",
-    "@babel/traverse": "^7.28.6",
+    "@babel/cli": "^8.0.0-rc.3 <8.0.0",
+    "@babel/core": "^8.0.0-rc.3 <8.0.0",
+    "@babel/generator": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-modules-commonjs": "^8.0.0-rc.3 <8.0.0",
+    "@babel/traverse": "^8.0.0-rc.3 <8.0.0",
     "@rollup/plugin-babel": "^7.0.0",
     "babel-loader": "^10.1.0",
     "rollup": "^4.59.0",

packages/babel-helper-define-polyfill-provider/src/index.ts

@@ -1,11 +1,10 @@
 import { declare } from "@babel/helper-plugin-utils";
 import type { NodePath } from "@babel/traverse";
 
-import _getTargets, {
+import getTargets, {
   isRequired,
   getInclusionReasons,
 } from "@babel/helper-compilation-targets";
-const getTargets = _getTargets.default || _getTargets;
 
 import { createUtilsGetter } from "./utils";
 import ImportsCachedInjector from "./imports-injector";

packages/babel-helper-define-polyfill-provider/test/helpers/ast-to-code-serializer.js

@@ -1,6 +1,7 @@
 import { types as t } from "@babel/core";
 import _generator from "@babel/generator";
-const generator = _generator.default;
+// For compatibility when running tests with Babel 7
+const generator = _generator.default || _generator;
 
 export default {
   test: v => t.isNode(v),

packages/babel-plugin-polyfill-corejs3/package.json

@@ -27,19 +27,19 @@
     "core-js-compat": "^3.48.0"
   },
   "devDependencies": {
-    "@babel/core": "^7.28.6",
-    "@babel/helper-plugin-test-runner": "^7.27.1",
-    "@babel/plugin-proposal-decorators": "^7.28.6",
-    "@babel/plugin-transform-class-properties": "^7.28.6",
-    "@babel/plugin-transform-classes": "^7.28.6",
-    "@babel/plugin-transform-for-of": "^7.27.1",
-    "@babel/plugin-transform-modules-commonjs": "^7.28.6",
-    "@babel/plugin-transform-runtime": "^7.28.5",
-    "@babel/plugin-transform-spread": "^7.28.6",
+    "@babel/core": "^8.0.0-rc.3 <8.0.0",
+    "@babel/helper-plugin-test-runner": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-proposal-decorators": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-class-properties": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-classes": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-for-of": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-modules-commonjs": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-runtime": "^8.0.0-rc.3 <8.0.0",
+    "@babel/plugin-transform-spread": "^8.0.0-rc.3 <8.0.0",
     "core-js": "^3.48.0",
     "core-js-pure": "^3.48.0"
   },
   "peerDependencies": {
-    "@babel/core": "^7.4.0 || ^8.0.0-0 <8.0.0"
+    "@babel/core": "^7.4.0 || ^8.0.0-rc.3"
   }
 }

packages/babel-plugin-polyfill-corejs3/src/index.ts

@@ -270,7 +270,7 @@ export default defineProvider<Options>(function (
                     coreJSPureHelper("get-iterator", useBabelRuntime, ext),
                     "getIterator",
                   ),
-                  [node.object],
+                  [node.object as t.Expression],
                 ),
               );
               path.skip();
@@ -345,7 +345,7 @@ export default defineProvider<Options>(function (
                 parentPath.type === "OptionalMemberExpression"
                   ? "MemberExpression"
                   : "CallExpression";
-              delete parentAsNotOptional.node.optional;
+              delete parentPath.node.optional;
 
               ({ parentPath } = parentPath);
             } while (
@@ -400,7 +400,7 @@ export default defineProvider<Options>(function (
           path.replaceWith(check(t.callExpression(id, [node.object])));
           if (t.isOptionalMemberExpression(parent)) parent.optional = true;
         } else {
-          path.replaceWith(t.callExpression(id, [node.object]));
+          path.replaceWith(t.callExpression(id, [node.object as t.Expression]));
         }
       }
     },

packages/babel-plugin-polyfill-corejs3/src/utils.ts

@@ -37,7 +37,11 @@ export function maybeMemoizeContext(
     context1 = t.cloneNode(object);
   } else {
     context2 = scope.generateDeclaredUidIdentifier("context");
-    context1 = t.assignmentExpression("=", t.cloneNode(context2), object);
+    context1 = t.assignmentExpression(
+      "=",
+      t.cloneNode(context2),
+      object as t.Expression,
+    );
   }
 
   return [context1, context2];

packages/babel-plugin-polyfill-corejs3/test/fixtures/absolute-imports/global/options.json

@@ -1,5 +1,6 @@
 {
   "externalHelpers": false,
+  "targets": { "ie": "5" },
   "plugins": [
     [
       "@@/polyfill-corejs3",