Frontend Engine

Overview

This project aims to create a shared frontend engine used by both the internal and external frontend applications.

The goal is to reduce duplicated code, improve consistency between applications, and simplify long-term maintenance while still allowing each application to evolve independently where needed.

Architecture Direction

The frontend engine will contain shared frontend functionality such as:

• shared components
• utilities
• validation
• queries and mutations
• presenters

The internal and external applications will continue to own:

• routes
• authentication
• app-specific pages and features

Development Approach

We are starting with a small incremental implementation rather than a full migration.

The initial focus is to:

• identify common frontend patterns
• extract reusable functionality into the engine
• prove the shared architecture works cleanly
• minimise disruption to the existing applications

Local Development

During development, the applications will consume the engine as a local package dependency.

Docker-based local development support will be used so engine changes can be picked up quickly during development.

Principles

• keep the implementation simple and explicit
• prefer shared reusable modules over duplication
• avoid premature abstraction
• maintain clear ownership boundaries between the engine and applications
• evolve incrementally

SonarQube Cloud scan

Run a local scan against SonarCloud for the current git branch. See the DEFRA SonarCloud guide for organisation access and CI setup.

Setup

1. Log in to SonarQube Cloud with your DEFRA GitHub account
2. Go to My Account → Security → Generate Tokens and create a personal token
3. Add SONAR_TOKEN=<your-token> to your .env file

Run

Generate test coverage first, then scan:

npm test
npm run sonar

The script uploads results for the current branch and prints:

• Quality gate pass/fail and failed conditions
• Open issues on new code (when the gate fails)
• Accepted / false-positive issues without comment — DEFRA quality gates require a justification comment on each suppressed issue; add comments in SonarCloud under the issue Activity tab

Exit code is 0 when the gate passes and all suppressed issues are commented, 1 otherwise.