ng add @angular/ssr fails with "Class extends value undefined is not a constructor or null" error

[liferays]

Command

add

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

The ng add @angular/ssr command consistently fails when trying to add server-side rendering to an existing Angular 19.2.14 project. The error occurs during the package loading
phase, specifically in the @listr2/prompt-adapter-inquirer dependency.

Root Cause Analysis

The issue appears to be in the @listr2/prompt-adapter-inquirer@2.0.18 package that's a dependency of @angular/cli@19.2.14. The error occurs at line 30:62 in the compiled JavaScript
where it's trying to extend a class that's undefined.

This suggests:

1. Missing or incompatible inquirer dependency
2. Version mismatch between @listr2/prompt-adapter-inquirer and its peer dependencies
3. Potential ESM/CommonJS module resolution issue

Minimal Reproduction

Steps to Reproduce

1. Create an Angular 19.2.14 project or use existing one
2. Run ng add @angular/ssr --project=
3. Error occurs during "Loading package information from registry" phase

Workaround

The issue can be bypassed by:

1. Manually installing @angular/ssr via npm install @angular/ssr --legacy-peer-deps
2. Manually creating the required SSR configuration files following the documentation
3. Updating angular.json manually for SSR build configuration

Expected Behavior

The ng add @angular/ssr command should successfully add server-side rendering support to the project without errors.

Exception or Error

Error Details

  $ ng add @angular/ssr --project=marketplace-app
  ✔ Determining Package Manager
    › Using package manager: npm
  ✔ Searching for compatible package version
    › Found compatible package version: @angular/ssr@19.2.14.
  ✔ Loading package information from registry
  ✖ Class extends value undefined is not a constructor or null
  An unhandled exception occurred: Class extends value undefined is not a constructor or null
  See "/tmp/ng-xYMb4w/angular-errors.log" for further details.

  Error Log Contents:
  [error] TypeError: Class extends value undefined is not a constructor or null
      at Object.<anonymous> (/home/ubuntu/xxxxx/node_modules/@listr2/prompt-adapter-inquirer/dist/index.cjs:30:62)
      at Module._compile (node:internal/modules/cjs/loader:1730:14)
      at Object..js (node:internal/modules/cjs/loader:1895:10)
      at Module.load (node:internal/modules/cjs/loader:1465:32)
      at Function._load (node:internal/modules/cjs/loader:1282:12)
      at TracingChannel.traceSync (node:diagnostics_channel:322:14)
      at wrapModuleLoad (node:internal/modules/cjs/loader:235:24)
      at Module.require (node:internal/modules/cjs/loader:1487:12)
      at require (node:internal/modules/helpers:135:16)
      at /home/ubuntu/xxxxx/node_modules/@angular/cli/src/commands/add/cli.js:265:108

Your Environment

Environment

  - Angular CLI: 19.2.14
  - Angular: 19.2.14
  - Node: (include your version)
  - Package Manager: npm
  - OS: Linux (WSL2)
  - Project: Multi-project workspace with existing Angular 19.2.14 applications

Anything else relevant?

Additional Context

• This issue persists even after clearing npm cache and reinstalling Angular CLI
• The error is consistent across multiple attempts
• Using --legacy-peer-deps for other npm operations works fine
• The project has some Angular 18-compatible dependencies that were temporarily removed to isolate the issue

Relevant Repository: https://github.com/angular/angular-cli
Component: ng add command / SSR schematic

[alan-agius4]

I'm sorry, but we can't reproduce the problem following the instructions you provided.
Remember that we have a large number of issues to resolve, and have only a limited amount of time to reproduce your issue.
Short, explicit instructions make it much more likely we'll be able to reproduce the problem so we can fix it.

If the problem persists, please open a new issue following our submission guidelines.

A good way to make a minimal repro is to create a new app via ng new repro-app and add the minimum possible code to show the problem. Then you can push this repository to github and link it here.