jest-resolve - only resolve realpath once in try-catch (#6925)

Fixes #6880

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 ### Fixes
 
+- `[jest-resolve]` Only resolve realpath once in try-catch ([#6925](https://github.com/facebook/jest/pull/6925))
 - `[expect]` Fix TypeError in `toBeInstanceOf` on `null` or `undefined` ([#6912](https://github.com/facebook/jest/pull/6912))
 - `[jest-jasmine2]` Throw a descriptive error if the first argument supplied to a hook was not a function ([#6917](https://github.com/facebook/jest/pull/6917))
 - `[jest-circus]` Throw a descriptive error if the first argument supplied to a hook was not a function ([#6917](https://github.com/facebook/jest/pull/6917))

packages/jest-resolve/src/__tests__/resolve.test.js

@@ -134,8 +134,9 @@ describe('resolveModule', () => {
     const resolver = new Resolver(moduleMap, {
       extensions: ['.js'],
     });
-    const src = require.resolve(
-      '../../src/__mocks__/bar/node_modules/foo/index.js',
+    const src = path.join(
+      path.resolve(__dirname, '../../src/__mocks__/bar/node_modules/'),
+      'foo/index.js',
     );
     const resolved = resolver.resolveModule(src, 'dep');
     expect(resolved).toBe(

packages/jest-resolve/src/node_modules_paths.js

@@ -38,17 +38,21 @@ export default function nodeModulesPaths(
     prefix = '\\\\';
   }
 
-  // The node resolution algorithm (as implemented by NodeJS
-  // and TypeScript) traverses parents of the physical path,
-  // not the symlinked path
-  const physicalBasedir = realpath(basedirAbs);
+  // The node resolution algorithm (as implemented by NodeJS and TypeScript)
+  // traverses parents of the physical path, not the symlinked path
+  let physicalBasedir;
+  try {
+    physicalBasedir = realpath(basedirAbs);
+  } catch (err) {
+    // realpath can throw, e.g. on mapped drives
+    physicalBasedir = basedirAbs;
+  }
 
   const paths = [physicalBasedir];
   let parsed = path.parse(physicalBasedir);
   while (parsed.dir !== paths[paths.length - 1]) {
-    const realParsedDir = realpath(parsed.dir);
-    paths.push(realParsedDir);
-    parsed = path.parse(realParsedDir);
+    paths.push(parsed.dir);
+    parsed = path.parse(parsed.dir);
   }
 
   const dirs = paths