feat: add reactive helper on

[JeanMeche]

An alternative to explicitEffect for explicit dependencies in an effect

[gemini-code-assist]

Summary of Changes

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This pull request introduces a new reactive helper, on, designed to enhance how effects are managed in Angular applications. It provides a more explicit and controlled mechanism for reacting to changes in signals, allowing developers to define specific dependencies and access historical values, thereby offering a powerful alternative to existing effect management patterns. This addition aims to improve the predictability and maintainability of reactive logic within Angular applications.

Highlights

• New Reactive Helper on: Introduced a new on reactive helper for Angular effects, providing an alternative to explicitEffect for managing explicit dependencies.
• Explicit Dependency Tracking: The on helper allows developers to explicitly define dependencies for an effect, supporting single signals, arrays of signals, or objects containing signals.
• Access to Previous Values: The effect callback function now receives both the current and previous input values, enabling more sophisticated state management and change detection logic.
• New Library Entry Point: A new secondary entry point ngxtension/reactive-on has been added to house this new functionality.

Changelog

• libs/ngxtension/reactive-on/README.md
  • Added a README file for the new reactive-on secondary entry point.
• libs/ngxtension/reactive-on/ng-package.json
  • Added Angular package configuration for the reactive-on library.
• libs/ngxtension/reactive-on/project.json
  • Added Nx project configuration for the reactive-on library.
• libs/ngxtension/reactive-on/src/index.ts
  • Exported the on helper from its source file.
• libs/ngxtension/reactive-on/src/on.spec.ts
  • Added comprehensive unit tests for the on helper, covering various dependency types and value tracking.
• libs/ngxtension/reactive-on/src/on.ts
  • Implemented the core on reactive helper, including type overloads and logic for handling different dependency structures and previous values.
• tsconfig.base.json
  • Updated the TypeScript path mappings to include the new ngxtension/reactive-on library.

Activity

• No specific activity (comments, reviews, or progress updates) has been recorded for this pull request yet.

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☁️ Nx Cloud last updated this comment at 2026-02-28 00:12:57 UTC

[gemini-code-assist]

Code Review

The pull request introduces a new reactive helper on which provides an alternative to explicitEffect for managing explicit dependencies in Angular effects. The implementation correctly handles single, array, and object-based signal dependencies, ensuring that effects only re-run when these explicit dependencies change, thanks to the appropriate use of untracked. The accompanying tests are comprehensive, covering various dependency types and the prevInput functionality, demonstrating the helper's intended behavior and robustness. The project setup and documentation are also correctly configured for the new library.