---

name: angular-15-to-16-upgrade description: Guide for incrementally upgrading Nx library peerDependencies from Angular 15 to support both 15 and 16. Use when upgrading Angular libraries in a monolith, making libs dual-compatible, or preparing for Angular 16 migration. allowed-tools: Read, Write, Edit, Bash, Glob, Grep

Angular 15→16 Library Upgrade (Incremental)

Guide for upgrading Nx libraries to be dual-compatible with Angular 15 and 16.

Strategy

Upgrade libraries one at a time while apps remain on Ng15. Libraries use widened peerDependencies to support both versions during transition.

Breaking Changes Summary

Prepare Ahead (Do While Still on Ng15)

These changes are safe to make now and will ease the final migration.

1. Remove Deprecated APIs (Removed in Ng16)

2. Verify All Deps Are Ivy-Only

ngcc removal is the #1 migration blocker. View Engine libraries won't work in Ng16.

Copy# Check for View Engine packages
grep -r "__ivy_ngcc__" node_modules/*/package.json
grep -r "ngcc" node_modules/*/package.json

If any deps still need ngcc, contact maintainers or find alternatives before upgrading.

3. Migrate Class Guards to Functional (Optional but Recommended)

Class-based guards/resolvers are deprecated in Ng16. Refactor now for both versions:

Copy// OLD: Class-based (deprecated in Ng16)
@Injectable({ providedIn: 'root' })
export class AuthGuard implements CanActivate {
  constructor(private auth: AuthService) {}
  canActivate(): boolean {
    return this.auth.isLoggedIn();
  }
}

// NEW: Functional (works in Ng15 and Ng16)
export const authGuard: CanActivateFn = () => {
  return inject(AuthService).isLoggedIn();
};

4. Widen PeerDeps (Safe Now)

This doesn't break Ng15 consumers:

Copy"peerDependencies": {
  "@angular/core": "^15.0.0 || ^16.0.0",
  "@angular/common": "^15.0.0 || ^16.0.0",
  "@angular/router": "^15.0.0 || ^16.0.0"
}

5. Update Third-Party Ecosystem Libs

Check Ng16 support for:

• @ngrx/*
• @angular/material / @angular/cdk
• ngx-* or @ngx-* packages
• primeng, etc.

Automatic Schematics (Run During ng update)

API Changes Reference

runInInjectionContext (Auto-migrated)

Copy// Ng15
injector.runInContext(() => { ... });

// Ng16
import { runInInjectionContext } from '@angular/core';
runInInjectionContext(injector, () => { ... });

No manual work needed - ng update handles this automatically.

New Optional APIs (Adopt When Ready)

These are new in Ng16 but not required for compatibility:

• DestroyRef - Cleaner cleanup pattern
• Input transforms - Transform decorator inputs
• Standalone components - Optional, NgModules still supported

Pre-flight Audit

Run before upgrading any library:

Copy./skills/angular-15-to-16-upgrade/scripts/audit-lib-compat.sh libs/my-lib

Checks:

• Current peerDependencies versions
• Deprecated API usage
• View Engine remnants
• Third-party Angular ecosystem deps

Upgrade Procedure

1. Audit the Library

Copy./skills/angular-15-to-16-upgrade/scripts/audit-lib-compat.sh libs/my-lib

2. Fix Blocking Issues (While on Ng15)

• Remove entryComponents, ANALYZE_FOR_ENTRY_COMPONENTS
• Replace ReflectiveInjector with Injector.create()
• Update or replace any View Engine deps

3. Widen PeerDeps

Copy"peerDependencies": {
  "@angular/core": "^15.0.0 || ^16.0.0",
  "@angular/common": "^15.0.0 || ^16.0.0"
}

4. Test Both Versions

Option A: CI Matrix

Copystrategy:
  matrix:
    angular: [15, 16]
steps:
  - run: npm install @angular/core@${{ matrix.angular }}
  - run: nx test my-lib

Option B: Local Verification

Copynx test my-lib  # Ng15

npm install @angular/core@16 @angular/common@16 --no-save
nx test my-lib  # Ng16
git checkout package-lock.json

5. Commit

Copygit commit -m "feat(my-lib): support Angular 15 and 16"

Full App Migration (When All Libs Ready)

Once all libraries are dual-compatible:

Copy# Nx
nx migrate @angular/core@16
nx migrate --run-migrations

# Or Angular CLI
ng update @angular/core@16 @angular/cli@16

Then remove ^15.0.0 || from library peerDependencies.

Troubleshooting

ngcc errors / View Engine errors

Library still uses View Engine. Options:

• Update to newer version of the library
• Find alternative package
• Fork and recompile as Ivy-only

"Cannot find module" errors

Third-party dep doesn't support Ng16:

• Check for updated version
• Use overrides in package.json as temporary workaround
• Find alternative

Type errors after upgrade

TypeScript version mismatch. Ng16 requires TS 4.9.3+.

Peer dependency conflicts

Use --legacy-peer-deps cautiously, or add overrides:

Copy"overrides": {
  "problematic-package": {
    "@angular/core": "$@angular/core"
  }
}