angular-modernization

Angular Modernization

Transforms legacy Angular components to modern architecture using a two-step approach:

Automated migrations - Angular CLI schematics for standalone, control flow, and signals
Bitwarden patterns - ADR compliance, OnPush change detection, proper visibility, thin components

Workflow

Step 1: Run Angular CLI Migrations

⚠️ CRITICAL: ALWAYS use Angular CLI migrations when available. DO NOT manually migrate features that have CLI schematics.

Angular provides automated schematics that handle edge cases, update tests, and ensure correctness. Manual migration should ONLY be used for patterns not covered by CLI tools.

IMPORTANT:

Always run the commands using npx ng.
All the commands must be run on directories and NOT files. Use the --path option to target directories.
Run migrations in order (some depend on others)

1. Standalone Components

npx ng generate @angular/core:standalone --path=<directory> --mode=convert-to-standalone

NgModule-based → standalone architecture

2. Control Flow Syntax

npx ng generate @angular/core:control-flow

*ngIf, *ngFor, *ngSwitch → @if, @for, @switch

3. Signal Inputs

npx ng generate @angular/core:signal-input-migration

@Input() → signal inputs

4. Signal Outputs

npx ng

@Output() → signal outputs

5. Signal Queries

@ViewChild, @ContentChild, etc. → signal queries

6. inject() Function

Constructor injection → inject() function

7. Self-Closing Tag

Updates templates to self-closing syntax

8. Unused Imports

Removes unused imports

Step 2: Apply Bitwarden Patterns

See migration-patterns.md for detailed examples.

Add OnPush change detection
Apply visibility modifiers (protected for template access, private for internal)
Convert local component state to signals
Keep service observables (don't convert to signals)
Extract business logic to services
Organize class members correctly
Update tests for standalone

Step 3: Validate

Fix linting and formatting using npm run lint:fix
Run tests using npm run test

If any errors occur, fix them accordingly.

Key Decisions

Signals vs Observables

Signals - Component-local state only (ADR-0027)
Observables - Service state and cross-component communication (ADR-0003)
Use toSignal() to bridge observables into signal-based components

Visibility

protected - Template-accessible members
private - Internal implementation

Other Rules

Always add OnPush change detection
No TypeScript enums (use const objects with type aliases per ADR-0025)
No code regions (refactor instead)
Thin components (business logic in services)

Validation Checklist

Before completing migration:

OnPush change detection added
Visibility modifiers applied (protected/private)
Signals for component state, observables for service state
Class members organized (see migration-patterns.md)
Tests updated and passing
No new TypeScript enums
No code regions

References

Bitwarden ADRs

Angular Resources