Remove ./src/* export from public build (#23262)

We only export the source directory so Jest and Rollup can access them
during local development and at build time. The files don't exist in the
public builds, so we don't need the export entry, either.

scripts/rollup/packaging.js

@@ -152,6 +152,7 @@ function filterOutEntrypoints(name) {
   let jsonPath = `build/node_modules/${name}/package.json`;
   let packageJSON = JSON.parse(readFileSync(jsonPath));
   let files = packageJSON.files;
+  let exportsJSON = packageJSON.exports;
   if (!Array.isArray(files)) {
     throw new Error('expected all package.json files to contain a files field');
   }
@@ -181,7 +182,6 @@ function filterOutEntrypoints(name) {
       unlinkSync(`build/node_modules/${name}/${filename}`);
       changed = true;
       // Remove it from the exports field too if it exists.
-      const exportsJSON = packageJSON.exports;
       if (exportsJSON) {
         if (filename === 'index.js') {
           delete exportsJSON['.'];
@@ -190,6 +190,15 @@ function filterOutEntrypoints(name) {
         }
       }
     }
+
+    // We only export the source directory so Jest and Rollup can access them
+    // during local development and at build time. The files don't exist in the
+    // public builds, so we don't need the export entry, either.
+    const sourceWildcardExport = './src/*';
+    if (exportsJSON && exportsJSON[sourceWildcardExport]) {
+      delete exportsJSON[sourceWildcardExport];
+      changed = true;
+    }
   }
   if (changed) {
     let newJSON = JSON.stringify(packageJSON, null, '  ');