Always use the new implementation

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

@@ -20,7 +20,7 @@ import {
   isLoose,
 } from "./features";
 
-export { FEATURES, injectInitialization };
+export { FEATURES, enableFeature, injectInitialization };
 
 // Note: Versions are represented as an integer. e.g. 7.1.5 is represented
 //       as 70000100005. This method is easier than using a semver-parsing

packages/babel-plugin-proposal-private-property-in-object/src/index.js

@@ -1,36 +1,17 @@
 /* eslint-disable @babel/development/plugin-name */
 
 import { declare } from "@babel/helper-plugin-utils";
-import {
-  createClassFeaturePlugin,
-  FEATURES,
-} from "@babel/helper-create-class-features-plugin";
-import { isRequired } from "@babel/helper-compilation-targets";
 
 import pluginPrivateIn from "./native-private-fields";
 
 export default declare((api, options) => {
   api.assertVersion(7);
 
-  const {
-    loose,
-    nativePrivateFields = !isRequired(
-      "proposal-private-methods",
-      api.targets(),
-    ),
-  } = options;
+  // NOTE: When using the class fields or private methods plugins,
+  // they will also take care of '#priv in obj' checks when visiting
+  // the ClassExpression or ClassDeclaration nodes.
+  // The visitor of this plugin is only effective when not compiling
+  // private fields and methods.
 
-  if (nativePrivateFields) return pluginPrivateIn(api);
-
-  return createClassFeaturePlugin({
-    name: "proposal-class-properties",
-
-    api,
-    feature: FEATURES.privateIn,
-    loose,
-
-    manipulateOptions(opts, parserOpts) {
-      parserOpts.plugins.push("privateIn");
-    },
-  });
+  return pluginPrivateIn(api, options);
 });

packages/babel-plugin-proposal-private-property-in-object/src/native-private-fields.js

@@ -1,7 +1,11 @@
 import syntaxPlugin from "@babel/plugin-syntax-private-property-in-object";
-import { injectInitialization as injectConstructorInit } from "@babel/helper-create-class-features-plugin";
+import {
+  enableFeature,
+  FEATURES,
+  injectInitialization as injectConstructorInit,
+} from "@babel/helper-create-class-features-plugin";
 
-export default function pluginPrivateIn({ types: t, template }) {
+export default function pluginPrivateIn({ types: t, template }, options) {
   const classWeakSets = new WeakMap();
   const fieldsWeakSets = new WeakMap();
 
@@ -68,6 +72,9 @@ export default function pluginPrivateIn({ types: t, template }) {
   return {
     name: "proposal-private-property-in-object",
     inherits: syntaxPlugin,
+    pre() {
+      enableFeature(this.file, FEATURES.privateIn, options.loose);
+    },
     visitor: {
       BinaryExpression(path) {
         const { node } = path;

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields-based-on-targets/node-10/options.json

@@ -1,5 +1,4 @@
 {
   "targets": { "node": 10 },
-  "plugins": ["proposal-private-property-in-object", "syntax-class-properties"],
-  "throws": "Class fields are not enabled. If you want to only compile '#priv in obj' checks, you can either pass the `nativePrivateFields: true` option to @babel/plugin-proposal-private-property-in-object or you can set the top-level 'targets' option to something that natively supports private fields and methods."
+  "plugins": ["proposal-private-property-in-object", "syntax-class-properties"]
 }

packages/babel-plugin-proposal-private-property-in-object/test/fixtures/to-native-fields-based-on-targets/node-10/output.js

@@ -0,0 +1,10 @@
+var _xBrandCheck = new WeakSet();
+
+class A {
+  #x = void _xBrandCheck.add(this);
+
+  test() {
+    _xBrandCheck.has(this);
+  }
+
+}