fix: get relative path in haste map

CHANGELOG.md

@@ -67,6 +67,7 @@
 - `[jest-resolve]` Fix not being able to resolve path to mapped file with custom platform ([#7312](https://github.com/facebook/jest/pull/7312))
 - `[jest-message-util]` Improve parsing of error messages for unusually formatted stack traces ([#7319](https://github.com/facebook/jest/pull/7319))
 - `[jest-runtime]` Ensure error message text is not lost on errors with code frames ([#7319](https://github.com/facebook/jest/pull/7319))
+- `[jest-haste-map]` Fix to resolve path that is start with words same as rootDir ([#7324](https://github.com/facebook/jest/pull/7324))
 
 ### Chore & Maintenance
 

packages/jest-haste-map/src/lib/__tests__/fast_path.test.js

@@ -26,6 +26,13 @@ describe('fastPath.relative', () => {
     const relativeFilename = path.join('..', 'baz', 'foobar');
     expect(relative(root, filename)).toBe(relativeFilename);
   });
+
+  it('should get relative paths outside the root when start with same word', () => {
+    const root = path.join(__dirname, 'foo', 'bar');
+    const filename = path.join(__dirname, 'foo', 'barbaz', 'foobar');
+    const relativeFilename = path.join('..', 'barbaz', 'foobar');
+    expect(relative(root, filename)).toBe(relativeFilename);
+  });
 });
 
 describe('fastPath.resolve', () => {

packages/jest-haste-map/src/lib/fast_path.js

@@ -11,7 +11,7 @@ import path from 'path';
 
 // rootDir and filename must be absolute paths (resolved)
 export function relative(rootDir: string, filename: string): string {
-  return filename.indexOf(rootDir) === 0
+  return filename.indexOf(rootDir + path.sep) === 0
     ? filename.substr(rootDir.length + 1)
     : path.relative(rootDir, filename);
 }