remove unused code

incubator/@react-native-webapis/battery-status/README.md

@@ -42,7 +42,7 @@ index 69ebd557..a012b7f5 100644
            { runtime: "automatic" },
          ],
          [require("@babel/plugin-transform-react-jsx-source")],
-+        [require("@rnx-kit/polyfills/babel-plugin")],
++        [require("@rnx-kit/polyfills")],
        ],
      },
    ],

incubator/polyfills/README.md

@@ -9,14 +9,9 @@
 
 🚧🚧🚧🚧🚧🚧🚧🚧🚧🚧🚧
 
-This is a polyfills "autolinker" for Metro. It works like native module
+This is a polyfills "autolinker" for React Native. It works like native module
 autolinking, but gathers polyfills from dependencies instead.
 
-> **Note**
->
-> This package is temporary. Ideally, this should be upstreamed to
-> `@react-native-community/cli`.
-
 ## Motivation
 
 Please read the
@@ -45,11 +40,12 @@ npm add --save-dev @rnx-kit/polyfills
     // babel.config.js
     module.exports = {
       presets: ["module:@react-native/babel-preset"],
-   +  plugins: [require("@rnx-kit/polyfills/babel-plugin")],
+   +  plugins: [require("@rnx-kit/polyfills")],
     };
    ```
 
-2. In your `index.js` (or `index.ts`), add the following comment:
+2. In your `index.ts` (or `index.js`), add the following comment at the top of
+   the file:
 
    ```
    // @react-native-webapis

incubator/polyfills/package.json

@@ -10,7 +10,6 @@
     "email": "microsoftopensource@users.noreply.github.com"
   },
   "files": [
-    "babel-plugin.js",
     "lib/*"
   ],
   "main": "lib/index.js",

incubator/polyfills/src/index.ts

@@ -1,40 +1,48 @@
+import type { ConfigAPI } from "@babel/core";
+import { types as t } from "@babel/core";
+import { declare } from "@babel/helper-plugin-utils";
+import babelTemplate from "@babel/template";
 import { getDependencyPolyfills } from "./dependency";
-import type { Context, GetPreludeModules } from "./types";
-
-/**
- * Ideally, we'd need something between `serializer.getPolyfills` and
- * `serializer.getModulesRunBeforeMainModule`. The former does not have access
- * to `require`, while the latter requires that the listed modules are
- * explicitly used in the bundle itself (see
- * https://github.com/facebook/metro/issues/850). For now, we will use this fact
- * to simply list all prelude modules.
- */
-function defaultModules({ projectRoot }: Context): string[] {
-  const platforms = [
-    "react-native",
-    "react-native-macos",
-    "react-native-windows",
-  ];
-  const options = { paths: [projectRoot] };
-
-  const modules = [];
-  for (const platform of platforms) {
-    const core = `${platform}/Libraries/Core/InitializeCore`;
-    try {
-      modules.push(require.resolve(core, options));
-    } catch (_) {
-      // ignore
-    }
-  }
-
-  return modules;
-}
-
-export const getPreludeModules: GetPreludeModules = () => {
-  const context = { projectRoot: process.cwd() };
-  const modules = defaultModules(context);
-  const dependencyPolyfills = getDependencyPolyfills(context);
-  return modules.concat(dependencyPolyfills);
-};
-
-export default getPreludeModules;
+
+module.exports = declare((api: ConfigAPI) => {
+  api.assertVersion(7);
+
+  const pluginName = "@react-native-webapis/polyfills";
+
+  let isPolyfilled: string | null = null;
+
+  return {
+    name: pluginName,
+    visitor: {
+      Program: (path, context) => {
+        const leadingComments = path.node.body[0]?.leadingComments;
+        const codegen = leadingComments?.some((comment) => {
+          const normalizedComment = comment.value.trim().split(" ")[0].trim();
+          return normalizedComment.startsWith("@react-native-webapis");
+        });
+
+        if (!codegen) {
+          return;
+        }
+
+        if (isPolyfilled != null) {
+          throw new Error(
+            `'${pluginName}' is already applied to ${isPolyfilled}`
+          );
+        }
+
+        isPolyfilled = context.file.opts.filename ?? "<unnamed module>";
+
+        const polyfills = getDependencyPolyfills({ projectRoot: context.cwd });
+        const importPolyfill = babelTemplate(`import %%source%%;`);
+
+        for (const polyfill of polyfills) {
+          path.unshiftContainer(
+            "body",
+            importPolyfill({ source: t.stringLiteral(polyfill) })
+          );
+        }
+      },
+    },
+  };
+});