Allow JS_DIR path to be relative to cwd (facebook#47877)

Summary:
Pull Request resolved: facebook#47877

Changelog: [internal]

Reviewed By: sammy-SC

Differential Revision: D66302814

fbshipit-source-id: 55d6f86d098673e28fad71a43863f2041810d04b

jest/integration/config/metro.config.js

@@ -17,17 +17,21 @@ const rnTesterConfig = getDefaultConfig(
   path.resolve('../../../packages/rn-tester'),
 );
 
+const JS_DIR = process.env.JS_DIR
+  ? path.resolve(process.cwd(), process.env.JS_DIR)
+  : null;
+
 const config = {
   projectRoot: path.resolve(__dirname, '../../..'),
   reporter: {
     update: () => {},
   },
   resolver: {
     blockList: /\/RendererProxy\.fb\.js$/, // Disable dependency injection for the renderer
-    disableHierarchicalLookup: !!process.env.JS_DIR,
+    disableHierarchicalLookup: !!JS_DIR,
     sourceExts: ['fb.js', ...rnTesterConfig.resolver.sourceExts],
-    nodeModulesPaths: process.env.JS_DIR
-      ? [path.join(process.env.JS_DIR, 'public', 'node_modules')]
+    nodeModulesPaths: JS_DIR
+      ? [path.join(JS_DIR, 'public', 'node_modules')]
       : [],
     hasteImplModulePath: path.resolve(__dirname, 'hasteImpl.js'),
   },
@@ -36,12 +40,12 @@ const config = {
     // using babel-register.
     babelTransformerPath: path.resolve(__dirname, 'metro-babel-transformer.js'),
   },
-  watchFolders: process.env.JS_DIR
+  watchFolders: JS_DIR
     ? [
-        path.join(process.env.JS_DIR, 'RKJSModules', 'vendor', 'react'),
-        path.join(process.env.JS_DIR, 'tools', 'metro'),
-        path.join(process.env.JS_DIR, 'node_modules'),
-        path.join(process.env.JS_DIR, 'public', 'node_modules'),
+        path.join(JS_DIR, 'RKJSModules', 'vendor', 'react'),
+        path.join(JS_DIR, 'tools', 'metro'),
+        path.join(JS_DIR, 'node_modules'),
+        path.join(JS_DIR, 'public', 'node_modules'),
       ]
     : [],
 };