Revert a windows dir normalization patch that is no longer needed aft…

…er upgrading babel

Reviewed By: rubennorte

Differential Revision: D8913980

fbshipit-source-id: 1adccc2804addbbeabc79c5f2000872a6e011fb4

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

@@ -55,21 +55,21 @@ function config(onlyList) {
  * have the same name as one of `BABEL_ENABLED_PATHS`.
  */
 function buildRegExps(basePath, dirPaths) {
+  // Babel `only` option works with forward slashes in the RegExp so replace
+  // them for Windows (only v7 beta 44 ~ 52 temporarily changes this behavior)
   return dirPaths.map(
     folderPath =>
-      // 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(
-            `^${escapeRegExp(path.resolve(basePath, '.') + path.sep)}${
-              folderPath.source // This is actual regex, don't escape it
-            }`,
-            folderPath.flags,
+            `^${escapeRegExp(
+              path.resolve(basePath, '.').replace(/\\/g, '/'),
+            )}/${folderPath.source}`,
           )
-        : new RegExp('^' + escapeRegExp(path.resolve(basePath, folderPath))),
+        : new RegExp(
+            `^${escapeRegExp(
+              path.resolve(basePath, folderPath).replace(/\\/g, '/'),
+            )}`,
+          ),
   );
 }