Fix regex paths for Windows

Reviewed By: davidaurelio

Differential Revision: D8735223

fbshipit-source-id: 646f03a6192699a8f890e19cdcafee1631332251

packages/metro-babel-register/src/babel-register.js

@@ -55,20 +55,19 @@ function config(onlyList) {
 function buildRegExps(basePath, dirPaths) {
   return dirPaths.map(
     folderPath =>
-      // Babel `only` option works with forward slashes in the RegExp so replace
-      // backslashes for Windows.
+      // Babel cares about windows/unix paths since v7b44
+      // https://github.com/babel/babel/issues/8184
+      // basePath + path.sep + dirPath/dirRegex
+      // /home/name/webroot/js + / + relative/path/to/exclude
+      // c:\home\name\webroot\js + \ + relative\path\to\exclude
       folderPath instanceof RegExp
         ? new RegExp(
-            `^${escapeRegExp(
-              path.resolve(basePath, '.').replace(/\\/g, '/'),
-            )}/${folderPath.source}`,
+            `^${escapeRegExp(path.resolve(basePath, '.') + path.sep)}${
+              folderPath.source // This is actual regex, don't escape it
+            }`,
             folderPath.flags,
           )
-        : new RegExp(
-            `^${escapeRegExp(
-              path.resolve(basePath, folderPath).replace(/\\/g, '/'),
-            )}`,
-          ),
+        : new RegExp('^' + escapeRegExp(path.resolve(basePath, folderPath))),
   );
 }