Updated create-app to use Yarn 4

Signed-off-by: Andre Wanlin <awanlin@spotify.com>

packages/create-app/src/lib/tasks.test.ts

@@ -227,27 +227,6 @@ describe('tasks', () => {
       );
     });
 
-    it('should error out on incorrect yarn version', async () => {
-      // requires callback implementation to support `promisify` wrapper
-      // https://stackoverflow.com/a/60579617/10044859
-      mockExec.mockImplementation((_command, callback) => {
-        callback(null, { stdout: '3.2.1', stderr: 'standard error' });
-      });
-
-      const appDir = 'projects/dir';
-      await expect(buildAppTask(appDir)).rejects.toThrow(
-        /^@backstage\/create-app requires Yarn v1, found '3\.2\.1'/,
-      );
-      expect(mockChdir).toHaveBeenCalledTimes(1);
-      expect(mockChdir).toHaveBeenNthCalledWith(1, appDir);
-      expect(mockExec).toHaveBeenCalledTimes(1);
-      expect(mockExec).toHaveBeenNthCalledWith(
-        1,
-        'yarn --version',
-        expect.any(Function),
-      );
-    });
-
     it('should fail if project directory does not exist', async () => {
       const appDir = 'projects/missingProject';
       await expect(buildAppTask(appDir)).rejects.toThrow(

packages/create-app/src/lib/tasks.ts

@@ -187,17 +187,6 @@ export async function checkPathExistsTask(path: string) {
 export async function buildAppTask(appDir: string) {
   process.chdir(appDir);
 
-  await Task.forItem('determining', 'yarn version', async () => {
-    const result = await exec('yarn --version');
-    const yarnVersion = result.stdout?.trim();
-
-    if (yarnVersion && !yarnVersion.startsWith('1.')) {
-      throw new Error(
-        `@backstage/create-app requires Yarn v1, found '${yarnVersion}'. You can migrate the project to Yarn 3 after creation using https://backstage.io/docs/tutorials/yarn-migration`,
-      );
-    }
-  });
-
   const runCmd = async (cmd: string) => {
     await Task.forItem('executing', cmd, async () => {
       await exec(cmd).catch(error => {