Incremental Migration and Version Upgrades

The Angular CLI provides automated migration schematics that handle mechanical refactors across major versions.

Common Migration Commands

# Update Angular packages
ng update @angular/cli @angular/core

# Migrate to standalone components
ng generate @angular/core:standalone

# Migrate to signal inputs
ng generate @angular/core:signal-input-migration

# Migrate to signal queries
ng generate @angular/core:signal-queries-migration

# Migrate to new control flow
ng generate @angular/core:control-flow-migration

# Migrate to inject()
ng generate @angular/core:inject-migration

Standalone Migration

# Convert NgModule-based app to standalone
ng generate @angular/core:standalone

This schematic:

1. Converts bootstrap to bootstrapApplication()
2. Removes AppModule
3. Adds standalone: true to components
4. Moves providers to app.config.ts

Signal Input Migration

# Convert @Input() to input()
ng generate @angular/core:signal-input-migration

Before:

@Input() title: string = '';

After:

title = input<string>('');

Modern Angular features can be adopted incrementally without a risky big-bang rewrite.

Incremental Signal Adoption

// Step 1: Add signals alongside existing code
@Component({...})
export class MyComponent {
  // Existing
  @Input() title: string = '';

  // New signal-based state
  count = signal(0);

  // Gradually migrate inputs to signals
  // title = input<string>('');
}

Incremental Standalone Adoption

// Convert components one at a time
@Component({
  selector: 'app-my-component',
  standalone: true,  // Add this
  imports: [CommonModule],  // Add explicit imports
  template: `...`,
})
export class MyComponent {}

Strict Mode

// tsconfig.json
{
  "compilerOptions": {
    "strict": true,
    "strictTemplates": true
  }
}

Strict mode and template type checking surface breakage before users ever see it.

Migration Planning

1. Audit — Identify deprecated APIs and patterns
2. Update — Run ng update to latest version
3. Migrate — Run schematics for mechanical changes
4. Adopt — Incrementally adopt new features (signals, standalone, control flow)
5. Verify — Run tests, lint, and build
6. Deploy — Ship incrementally with feature flags