[babel 8] Other Babel 8 misc changes

babel.config.js

@@ -27,7 +27,7 @@ module.exports = function (api) {
     exclude: [
       "transform-typeof-symbol",
       // We need to enable useBuiltIns
-      "proposal-object-rest-spread",
+      "transform-object-rest-spread",
     ],
   };
 

packages/babel-core/src/config/files/module-types.ts

@@ -29,19 +29,33 @@ export const supportsESM = semver.satisfies(
 export default function* loadCodeDefault(
   filepath: string,
   asyncError: string,
-  // TODO(Babel 8): Remove this
-  fallbackToTranspiledModule: boolean = false,
 ): Handler<unknown> {
   switch (path.extname(filepath)) {
     case ".cjs":
-      return loadCjsDefault(filepath, fallbackToTranspiledModule);
+      if (process.env.BABEL_8_BREAKING) {
+        return loadCjsDefault(filepath);
+      } else {
+        return loadCjsDefault(
+          filepath,
+          // @ts-ignore(Babel 7 vs Babel 8) Removed in Babel 8
+          /* fallbackToTranspiledModule */ arguments[2],
+        );
+      }
     case ".mjs":
       break;
     case ".cts":
       return loadCtsDefault(filepath);
     default:
       try {
-        return loadCjsDefault(filepath, fallbackToTranspiledModule);
+        if (process.env.BABEL_8_BREAKING) {
+          return loadCjsDefault(filepath);
+        } else {
+          return loadCjsDefault(
+            filepath,
+            // @ts-ignore(Babel 7 vs Babel 8) Removed in Babel 8
+            /* fallbackToTranspiledModule */ arguments[2],
+          );
+        }
       } catch (e) {
         if (e.code !== "ERR_REQUIRE_ESM") throw e;
       }
@@ -122,13 +136,14 @@ function loadCtsDefault(filepath: string) {
   }
 }
 
-function loadCjsDefault(filepath: string, fallbackToTranspiledModule: boolean) {
+function loadCjsDefault(filepath: string) {
   const module = endHiddenCallStack(require)(filepath);
   if (process.env.BABEL_8_BREAKING) {
     return module?.__esModule ? module.default : module;
   } else {
     return module?.__esModule
-      ? module.default || (fallbackToTranspiledModule ? module : undefined)
+      ? module.default ||
+          /* fallbackToTranspiledModule */ (arguments[1] ? module : undefined)
       : module;
   }
 }

packages/babel-core/src/config/files/plugins.ts

@@ -217,16 +217,26 @@ function* requireModule(type: string, name: string): Handler<unknown> {
     if (!process.env.BABEL_8_BREAKING) {
       LOADING_MODULES.add(name);
     }
-    return yield* loadCodeDefault(
-      name,
-      `You appear to be using a native ECMAScript module ${type}, ` +
-        "which is only supported when running Babel asynchronously.",
-      // For backward compatibility, we need to support malformed presets
-      // defined as separate named exports rather than a single default
-      // export.
-      // See packages/babel-core/test/fixtures/option-manager/presets/es2015_named.js
-      true,
-    );
+
+    if (process.env.BABEL_8_BREAKING) {
+      return yield* loadCodeDefault(
+        name,
+        `You appear to be using a native ECMAScript module ${type}, ` +
+          "which is only supported when running Babel asynchronously.",
+      );
+    } else {
+      return yield* loadCodeDefault(
+        name,
+        `You appear to be using a native ECMAScript module ${type}, ` +
+          "which is only supported when running Babel asynchronously.",
+        // For backward compatibility, we need to support malformed presets
+        // defined as separate named exports rather than a single default
+        // export.
+        // See packages/babel-core/test/fixtures/option-manager/presets/es2015_named.js
+        // @ts-ignore(Babel 7 vs Babel 8) This param has been removed
+        true,
+      );
+    }
   } catch (err) {
     err.message = `[BABEL]: ${err.message} (While processing: ${name})`;
     throw err;

packages/babel-core/src/config/item.ts

@@ -64,7 +64,7 @@ class ConfigItem {
    */
   _descriptor: UnloadedDescriptor;
 
-  // TODO(Babel 8): Check if this symbol needs to be updated
+  // TODO(Babel 9): Check if this symbol needs to be updated
   /**
    * Used to detect ConfigItem instances from other Babel instances.
    */

packages/babel-core/src/transformation/plugin-pass.ts

@@ -38,11 +38,6 @@ export default class PluginPass {
     return this.file.addHelper(name);
   }
 
-  // TODO: Remove this in Babel 8
-  addImport() {
-    this.file.addImport();
-  }
-
   buildCodeFrameError(
     node: NodeLocation | undefined | null,
     msg: string,
@@ -53,9 +48,14 @@ export default class PluginPass {
 }
 
 if (!process.env.BABEL_8_BREAKING) {
-  (PluginPass as any).prototype.getModuleName = function getModuleName():
-    | string
-    | undefined {
+  (PluginPass as any).prototype.getModuleName = function getModuleName(
+    this: PluginPass,
+  ): string | undefined {
     return this.file.getModuleName();
   };
+  (PluginPass as any).prototype.addImport = function addImport(
+    this: PluginPass,
+  ): void {
+    this.file.addImport();
+  };
 }

packages/babel-helper-create-class-features-plugin/src/index.ts

@@ -38,10 +38,12 @@ export function createClassFeaturePlugin({
   feature,
   loose,
   manipulateOptions,
-  // @ts-ignore(Babel 7 vs Babel 8) TODO(Babel 8): Remove the default value
-  api = { assumption: () => void 0 },
+  api,
   inherits,
 }: Options): PluginObject {
+  if (!process.env.BABEL_8_BREAKING) {
+    api ??= { assumption: () => void 0 as any } as any;
+  }
   const setPublicClassFields = api.assumption("setPublicClassFields");
   const privateFieldsAsSymbols = api.assumption("privateFieldsAsSymbols");
   const privateFieldsAsProperties = api.assumption("privateFieldsAsProperties");

packages/babel-plugin-transform-arrow-functions/src/index.ts

@@ -18,15 +18,23 @@ export default declare((api, options: Options) => {
         // was queued up.
         if (!path.isArrowFunctionExpression()) return;
 
-        path.arrowFunctionToExpression({
-          // While other utils may be fine inserting other arrows to make more transforms possible,
-          // the arrow transform itself absolutely cannot insert new arrow functions.
-          allowInsertArrow: false,
-          noNewArrows,
+        if (process.env.BABEL_8_BREAKING) {
+          path.arrowFunctionToExpression({
+            // While other utils may be fine inserting other arrows to make more transforms possible,
+            // the arrow transform itself absolutely cannot insert new arrow functions.
+            allowInsertArrow: false,
+            noNewArrows,
+          });
+        } else {
+          path.arrowFunctionToExpression({
+            allowInsertArrow: false,
+            noNewArrows,
 
-          // TODO(Babel 8): This is only needed for backward compat with @babel/traverse <7.13.0
-          specCompliant: !noNewArrows,
-        });
+            // This is only needed for backward compat with @babel/traverse <7.13.0
+            // @ts-ignore(Babel 7 vs Babel 8) Removed in Babel 8
+            specCompliant: !noNewArrows,
+          });
+        }
       },
     },
   };

packages/babel-plugin-transform-computed-properties/src/index.ts

@@ -17,15 +17,18 @@ type PropertyInfo = {
   state: PluginPass;
 };
 
-// TODO(Babel 8): Remove this
-const DefineAccessorHelper = template.expression.ast`
-function (type, obj, key, fn) {
-  var desc = { configurable: true, enumerable: true };
-  desc[type] = fn;
-  return Object.defineProperty(obj, key, desc);
-}`;
-// @ts-expect-error undocumented _compact node property
-DefineAccessorHelper._compact = true;
+if (!process.env.BABEL_8_BREAKING) {
+  // eslint-disable-next-line no-var
+  var DefineAccessorHelper = template.expression.ast`
+    function (type, obj, key, fn) {
+      var desc = { configurable: true, enumerable: true };
+      desc[type] = fn;
+      return Object.defineProperty(obj, key, desc);
+    }
+  `;
+  // @ts-expect-error undocumented _compact node property
+  DefineAccessorHelper._compact = true;
+}
 
 export default declare((api, options: Options) => {
   api.assertVersion(7);
@@ -44,26 +47,34 @@ export default declare((api, options: Options) => {
     key: t.Expression,
     fn: t.Expression,
   ) {
-    let helper: t.Identifier;
-    if (state.availableHelper("defineAccessor")) {
-      helper = state.addHelper("defineAccessor");
+    if (process.env.BABEL_8_BREAKING) {
+      return t.callExpression(state.addHelper("defineAccessor"), [
+        t.stringLiteral(type),
+        obj,
+        key,
+        fn,
+      ]);
     } else {
-      // Fallback for @babel/helpers <= 7.20.6, manually add helper function
-      // TODO(Babel 8): Remove this
-      const file = state.file;
-      helper = file.get("fallbackDefineAccessorHelper");
-      if (!helper) {
-        const id = file.scope.generateUidIdentifier("defineAccessor");
-        file.scope.push({
-          id,
-          init: DefineAccessorHelper,
-        });
-        file.set("fallbackDefineAccessorHelper", (helper = id));
+      let helper: t.Identifier;
+      if (state.availableHelper("defineAccessor")) {
+        helper = state.addHelper("defineAccessor");
+      } else {
+        // Fallback for @babel/helpers <= 7.20.6, manually add helper function
+        const file = state.file;
+        helper = file.get("fallbackDefineAccessorHelper");
+        if (!helper) {
+          const id = file.scope.generateUidIdentifier("defineAccessor");
+          file.scope.push({
+            id,
+            init: DefineAccessorHelper,
+          });
+          file.set("fallbackDefineAccessorHelper", (helper = id));
+        }
+        helper = t.cloneNode(helper);
       }
-      helper = t.cloneNode(helper);
-    }
 
-    return t.callExpression(helper, [t.stringLiteral(type), obj, key, fn]);
+      return t.callExpression(helper, [t.stringLiteral(type), obj, key, fn]);
+    }
   }
 
   /**

packages/babel-plugin-transform-for-of/src/index.ts

@@ -50,11 +50,13 @@ export default declare((api, options: Options) => {
       );
     }
 
-    // TODO: Remove in Babel 8
-    if (allowArrayLike && /^7\.\d\./.test(api.version)) {
-      throw new Error(
-        `The allowArrayLike is only supported when using @babel/core@^7.10.0`,
-      );
+    if (!process.env.BABEL_8_BREAKING) {
+      // TODO: Remove in Babel 8
+      if (allowArrayLike && /^7\.\d\./.test(api.version)) {
+        throw new Error(
+          `The allowArrayLike is only supported when using @babel/core@^7.10.0`,
+        );
+      }
     }
   }
 
@@ -217,10 +219,12 @@ export default declare((api, options: Options) => {
           return;
         }
 
-        if (!state.availableHelper(builder.helper)) {
-          // Babel <7.9.0 doesn't support this helper
-          transformWithoutHelper(skipIteratorClosing, path, state);
-          return;
+        if (!process.env.BABEL_8_BREAKING) {
+          if (!state.availableHelper(builder.helper)) {
+            // Babel <7.9.0 doesn't support this helper
+            transformWithoutHelper(skipIteratorClosing, path, state);
+            return;
+          }
         }
 
         const { node, parent, scope } = path;

packages/babel-plugin-transform-for-of/src/no-helper-implementation.ts

@@ -3,7 +3,7 @@ import type { NodePath } from "@babel/traverse";
 
 // This is the legacy implementation, which inlines all the code.
 // It must be kept for compatibility reasons.
-// TODO(Babel 8): Remove this code.
+// TODO(Babel 8): Remove this file.
 
 export default function transformWithoutHelper(
   loose: boolean | void,

packages/babel-plugin-transform-regenerator/src/index.ts

@@ -14,11 +14,13 @@ export default declare(({ types: t, assertVersion }) => {
       // We visit MemberExpression so that we always transform
       // regeneratorRuntime before babel-plugin-polyfill-regenerator.
       MemberExpression(path) {
-        if (!this.availableHelper?.("regeneratorRuntime")) {
-          // When using an older @babel/helpers version, fallback
-          // to the old behavior.
-          // TODO: Remove this in Babel 8.
-          return;
+        if (!process.env.BABEL_8_BREAKING) {
+          if (!this.availableHelper?.("regeneratorRuntime")) {
+            // When using an older @babel/helpers version, fallback
+            // to the old behavior.
+            // TODO: Remove this in Babel 8.
+            return;
+          }
         }
 
         const obj = path.get("object");
@@ -27,13 +29,15 @@ export default declare(({ types: t, assertVersion }) => {
             | t.Identifier
             | t.ArrowFunctionExpression;
 
-          if (
-            // TODO: Remove this in Babel 8, it's necessary to
-            // avoid the IIFE when using older Babel versions.
-            t.isArrowFunctionExpression(helper)
-          ) {
-            obj.replaceWith(helper.body);
-            return;
+          if (!process.env.BABEL_8_BREAKING) {
+            if (
+              // TODO: Remove this in Babel 8, it's necessary to
+              // avoid the IIFE when using older Babel versions.
+              t.isArrowFunctionExpression(helper)
+            ) {
+              obj.replaceWith(helper.body);
+              return;
+            }
           }
 
           obj.replaceWith(t.callExpression(helper, []));

packages/babel-plugin-transform-unicode-escapes/src/index.ts

@@ -9,11 +9,15 @@ export default declare(api => {
   const unicodeEscape = /(\\+)u\{([0-9a-fA-F]+)\}/g;
 
   function escape(code: number) {
-    let str = code.toString(16);
-    // Sigh, node 6 doesn't have padStart
-    // TODO: Remove in Babel 8, when we drop node 6.
-    while (str.length < 4) str = "0" + str;
-    return "\\u" + str;
+    if (process.env.BABEL_8_BREAKING) {
+      return "\\u" + code.toString(16).padStart(4, "0");
+    } else {
+      let str = code.toString(16);
+      // Sigh, node 6 doesn't have padStart
+      // TODO: Remove in Babel 8, when we drop node 6.
+      while (str.length < 4) str = "0" + str;
+      return "\\u" + str;
+    }
   }
 
   function replacer(match: string, backslashes: string[], code: string) {

packages/babel-preset-env/src/normalize-options.ts

@@ -82,14 +82,14 @@ const expandIncludesAndExcludes = (
     } else {
       re = filter;
     }
-    const items = filterableItems.filter(
-      item =>
-        re.test(item) ||
-        // For backwards compatibility, we also support matching against the
-        // proposal- name.
-        // TODO(Babel 8): Remove this.
-        re.test(item.replace(/^transform-/, "proposal-")),
-    );
+    const items = filterableItems.filter(item => {
+      return process.env.BABEL_8_BREAKING
+        ? re.test(item)
+        : re.test(item) ||
+            // For backwards compatibility, we also support matching against the
+            // proposal- name.
+            re.test(item.replace(/^transform-/, "proposal-"));
+    });
     if (items.length === 0) invalidFilters.push(filter);
     return items;
   });