Conditional middleware execution

[shamoo53]

🚀 PR: Add Conditional Middleware Execution (unless & onlyFor)

🧭 Overview

This PR introduces conditional middleware execution utilities that allow developers to selectively apply or skip middleware based on route patterns. This significantly improves developer experience (DX) by removing the need for complex guard-based workarounds.

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🎯 Problem

In the current setup:

• Middleware is applied globally or per route without flexibility
• Developers must use awkward guards or manual checks to exclude routes
• No built-in support for conditional middleware execution

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💡 Solution

• Introduce two reusable helpers:

  • unless() → skips middleware for specified routes
  • onlyFor() → applies middleware only to specified routes

• Support flexible route matching using:

  • Exact paths
  • Regular expressions
  • Glob patterns (via micromatch)

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🛠 Scope of Work

⚙️ Conditional Middleware Utilities

• Created src/middleware/utils/conditional.middleware.ts

• Implemented:

  • unless(middleware, patterns)
  • onlyFor(middleware, patterns) (inverse logic)

🔍 Route Matching Support

• Added support for:

  • Exact string paths ('/health')
  • Regex patterns (/^\/api\/v1/)
  • Glob patterns ('/api/**') using micromatch

⚡ Performance Consideration

• Designed as a stateless higher-order wrapper
• Ensures zero/minimal overhead on non-matching routes

📦 Exports

• Exported both helpers from src/index.ts for easy consumption

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📊 Acceptance Criteria

• ✔️ unless(['/health']) skips middleware for specified routes
• ✔️ Supports exact string, regex, and glob pattern matching
• ✔️ No measurable overhead on non-matching routes
• ✔️ Both helpers are exported from src/index.ts

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🧪 Testing

• Added unit tests for:

  • Matching logic (string, regex, glob)
  • unless() behavior
  • onlyFor() behavior

• Added integration tests to verify:

  • Middleware is skipped/applied correctly in real request flows

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📚 Usage Example

import { unless, onlyFor } from '@/middleware/utils/conditional.middleware';

// Skip middleware for health and metrics
app.use(unless(authMiddleware, ['/health', '/metrics']));

// Apply middleware only for API routes
app.use(onlyFor(authMiddleware, ['/api/**']));

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🏁 Summary

This PR adds a powerful and flexible middleware control layer, improving code clarity, reducing boilerplate, and enabling cleaner route-based logic in NestJS applications.
Closes #354
Closes #351
Closes #318
Closes #314

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