SonarJS Rules for Frontend Assets in .NET Repositories

Trigger On

• the repo already uses SonarQube, SonarCloud, or eslint-plugin-sonarjs
• the user asks for frontend code smells, cognitive complexity limits, or deeper bug-risk rules beyond base ESLint
• maintainability and reliability findings on JS or TS code should become a review or CI gate

Do Not Use For

• repos that want only a lightweight base lint setup with no extra smell or complexity rules
• teams that reject SonarQube, SonarCloud, or source-available SonarJS-derived tooling as a default gate
• cases where the problem is runtime page quality rather than source-level maintainability

Inputs

• the nearest AGENTS.md
• package.json
• existing ESLint config
• any SonarQube, SonarCloud, or scanner config already present in CI

mermaid
flowchart LR
  A["Need Sonar-style checks in a .NET repo frontend"] --> B{"Local developer loop or existing server gate?"}
  B -->|Local| C["Install eslint-plugin-sonarjs"]
  C --> D["Run through the normal eslint command"]
  B -->|Existing SonarQube or SonarCloud gate| E["Keep full analysis in the existing scanner pipeline"]
  D --> F["Phase rules and fix code"]
  E --> F

Workflow

1. Decide the execution path first:

• local developer loop through eslint-plugin-sonarjs
• server-side analysis through an already adopted SonarQube or SonarCloud pipeline

1. For local work, treat SonarJS as an ESLint extension rather than a standalone CLI.
2. Keep the first rollout narrow:

• bug-prone rules
• cognitive complexity
• duplicated branching or suspicious control flow

1. Add rules to the existing ESLint command instead of inventing a parallel local lint entrypoint.
2. If the repo already has SonarQube or SonarCloud, align local rule expectations with the server gate instead of maintaining two conflicting policies.
3. Fix code or phase rules deliberately; do not hide the first rollout behind broad disables.
4. Document licensing or hosting caveats before making Sonar-based tooling the default quality gate.

Current Upstream Notes

• SonarJS 13.6 adds rules for shallow-clone mutation, Vue class/mixin and state mutation, native alternatives to jQuery, Testing Library disappearance and synchronous-query patterns, Vitest vi.mock scope, and Playwright networkidle usage.
• The release also reduces false positives across Vue, React, testing, and TypeScript analysis. Re-run server analysis before preserving suppressions, and review new findings as behavior-specific guidance rather than enabling every new rule blindly.

Bootstrap When Missing

1. Detect current state:

• rg --files -g 'package.json' -g 'eslint.config.*' -g '.eslintrc*'
• rg -n '"eslint-plugin-sonarjs"|"sonar"|"sonarqube"|"sonarcloud"' .

1. Prefer the local ESLint-plugin path for developer workflows:

• npm install --save-dev eslint-plugin-sonarjs

1. Add the plugin and selected rules to the checked-in ESLint config.
2. Verify with the repo's normal lint entrypoint, for example:

• npx eslint .

1. If the repo already uses SonarQube or SonarCloud, keep the full analysis in that existing CI path instead of inventing a new local scanner flow.
2. Return status: configured if SonarJS-derived checks now have explicit ownership, or status: improved if an existing setup was tightened.
3. Return status: not_applicable when the repo explicitly chooses a purely OSS lint baseline without Sonar-based extensions.

Handle Failures

• There is no separate local sonarjs CLI from this repo; local developer use should go through ESLint with eslint-plugin-sonarjs.
• Plugin-load failures usually mean the ESLint config does not match the installed plugin version or plugin registration syntax.
• If the first rollout produces too many smells, phase rule adoption instead of disabling the plugin wholesale.
• If SonarQube or SonarCloud disagrees with local lint output, treat the server gate as the source of truth and align the local config deliberately.

Deliver

• explicit SonarJS-derived rule ownership
• a clear split between local ESLint-based use and any existing server-side Sonar pipeline
• documented rollout scope and caveats

Validate

• local developer commands still use the repo's standard ESLint entrypoint
• Sonar-based rules are not treated as a standalone local CLI when none exists
• licensing or hosting caveats are documented before broad adoption
• findings are actionable and phased instead of silently suppressed

Ralph Loop

1. Plan: analyze current state, target outcome, constraints, and risks.
2. Execute one step and produce a concrete delta.
3. Review the result and capture findings.
4. Apply fixes in small batches and rerun checks.
5. Update the plan after each iteration.
6. Repeat until outcomes are acceptable.
7. If a dependency is missing, bootstrap it or return status: not_applicable with a reason.

Required Result Format

• status: complete | clean | improved | configured | not_applicable | blocked
• plan: concise plan and current step
• actions_taken: concrete changes made
• verification: commands, checks, or review evidence
• remaining: unresolved items or none

Example Requests

• "Add SonarJS rules to the existing ESLint setup."
• "Use cognitive complexity checks on the frontend."
• "Explain whether we should use the ESLint plugin or SonarQube here."