Add a 'whitelist' option for the external-helpers plugin to mirror the helper builder. (#8531)

packages/babel-plugin-external-helpers/src/index.js

@@ -4,7 +4,18 @@ import { types as t } from "@babel/core";
 export default declare((api, options) => {
   api.assertVersion(7);
 
-  const { helperVersion = "7.0.0-beta.0" } = options;
+  const { helperVersion = "7.0.0-beta.0", whitelist = false } = options;
+
+  if (
+    whitelist !== false &&
+    (!Array.isArray(whitelist) || whitelist.some(w => typeof w !== "string"))
+  ) {
+    throw new Error(
+      ".whitelist must be undefined, false, or an array of strings",
+    );
+  }
+
+  const helperWhitelist = whitelist ? new Set(whitelist) : null;
 
   return {
     pre(file) {
@@ -19,6 +30,12 @@ export default declare((api, options) => {
           return;
         }
 
+        // babelCore.buildExternalHelpers() allows a whitelist of helpers that
+        // will be inserted into the external helpers list. That same whitelist
+        // should be passed into the plugin here in that case, so that we can
+        // avoid referencing 'babelHelpers.XX' when the helper does not exist.
+        if (helperWhitelist && !helperWhitelist.has(name)) return;
+
         return t.memberExpression(
           t.identifier("babelHelpers"),
           t.identifier(name),