How To Use Rules

Once you’ve created HTTP rules, you need to integrate them into your API projects. This guide covers loading rules, configuration, and common usage patterns.

Loading Rules

There are two ways to load rules into Thymian:

1. Via Configuration File

Create a thymian.config.yaml file in your project root:

ruleSets:
  - './rules/**/*.rule.js' # Local rules
  - '@thymian/rules-rfc-9110' # Npm package

plugins:
  '@thymian/plugin-http-linter': {}

2. Via CLI flags

npx thymian lint --rule-set @thymian/rules-rfc-9110

Creating Your Own Rule Set

File Structure

Organize your rule set as an npm package:

my-api-rules/
├── package.json
├── src/
│   ├── index.ts
│   └── rules/
│       ├── authentication/
│       │   └── require-bearer-token.rule.ts
│       ├── headers/
│       │   └── require-correlation-id.rule.ts
│       └── versioning/
│           └── check-api-version.rule.ts
└── tsconfig.json

Package Definition

package.json:

{
  "name": "@mycompany/api-rules",
  "version": "1.0.0",
  "main": "./dist/index.js",
  "types": "./dist/index.d.ts",
  "files": ["dist"],
  "peerDependencies": {
    "@thymian/plugin-http-linter": "^0.0.1",
    "@thymian/core": "^0.0.1"
  }
}

Rule Set Entry Point

src/index.ts:

import type { RuleSet } from '@thymian/core';

const myCompanyRules: RuleSet = {
  name: '@mycompany/api-rules',
  url: 'https://api-guidelines.mycompany.com',
  pattern: 'rules/**/*.rule.js', // Glob pattern for built rules
};

export default myCompanyRules;

Using Your Rule Set

After publishing your rule set to npm, install it in your project:

npm install @mycompany/api-rules

ruleSets:
  - '@mycompany/api-rules'

List Loaded Rules

See which rules are loaded:

thymian rules list

Or with specific rule sources:

thymian rules list --rule-set ./rules/**/*.rule.ts

Troubleshooting

Rules Not Loading

Problem: Rules aren’t being loaded

Solutions:

1. Check the glob pattern matches your files:

ls -la ./rules/**/*.rule.ts

2. Verify the rule exports default:

export default httpRule('...'); // ✅ Correct
export const myRule = httpRule('...'); // ❌ Wrong

3. Check for TypeScript compilation errors:

tsc --noEmit

Next Steps

• Explore the CLI commands for managing rules
• Learn about creating custom rules
• See combining rule types for hybrid validation