feat(utils): improve TypeScript type safety in cn utility

[sarv-tech]

Summary

fix #10

This PR improves type safety for the cn utility by replacing permissive type structures with stricter TypeScript definitions, adding comprehensive test coverage, and enhancing developer documentation while preserving existing runtime behavior.

Changes Made

Type Safety Improvements (src/utils/cn.ts)

• Replaced generic ClassValue usage with stricter custom type definitions.
• Updated conditional class object typing from Record<string, any> to Record<string, unknown>.
• Refactored recursive array typing to avoid TypeScript cyclic reference issues.
• Explicitly defined the function return type as string.
• Preserved compatibility with existing clsx and tailwind-merge behavior.

Unit Tests (src/utils/cn.test.ts)

Added a dedicated Vitest test suite covering:

• Standard class string merging
• Conditional class objects
• Nested class arrays
• null and undefined inputs
• Boolean conditional expressions
• Numeric values
• Empty values and invalid inputs
• Tailwind class conflict resolution via tailwind-merge

Test Configuration (tsconfig.app.json)

• Added testing-related type definitions required by Vitest.
• Updated TypeScript configuration to include project test files.
• Ensured type safety across the test environment.

Why This Change?

The previous implementation relied on permissive typing that could allow invalid values to be passed without TypeScript warnings. This update strengthens compile-time validation while maintaining identical runtime behavior.

Testing

• ✅ All new cn utility tests pass locally.
• ✅ Existing project test suite passes locally.
• ✅ No runtime regressions observed.
• ✅ Backward compatibility maintained.

Acceptance Criteria

• ✅ Improved TypeScript type safety for cn
• ✅ Added edge-case unit tests
• ✅ Graceful handling of invalid inputs
• ✅ Updated developer documentation
• ✅ Maintained backward compatibility

Notes for Reviewers

This change is focused exclusively on improving the safety, maintainability, and test coverage of the cn utility. The underlying implementation continues to use the existing twMerge(clsx(...)) pipeline, so no visual or behavioral changes are expected in existing components.

[gemini-code-assist]

Code Review

This pull request introduces unit tests for the cn utility function, refactors the utility to use stricter TypeScript types, and updates the TypeScript configuration to include test files and types. The review feedback suggests further tightening the StrictClassDictionary type to prevent runtime bugs from non-primitive values, and recommends removing test-specific types from the main application configuration (tsconfig.app.json) to avoid polluting the global namespace.

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[Copilot]

Pull request overview

This PR tightens the TypeScript typing around the cn className utility, adds a Vitest suite to validate its runtime behavior, and updates the app TypeScript config to typecheck tests with the appropriate test-related ambient types.

Changes:

• Replaced ClassValue usage with custom StrictClassValue types and updated cn to call clsx(...inputs) and return string.
• Added src/utils/cn.test.ts covering common cn usage patterns and Tailwind conflict resolution.
• Expanded tsconfig.app.json to include the tests directory and added Vitest / jest-dom types; added a new package-lock.json.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

File	Description
tsconfig.app.json	Includes tests in TS project and adds test-related types for Vitest/jest-dom.
src/utils/cn.ts	Introduces stricter cn input types + JSDoc updates; keeps twMerge(clsx(...)) pipeline.
src/utils/cn.test.ts	Adds Vitest coverage for cn behavior, including Tailwind merge behavior.
package-lock.json	Adds an npm lockfile (in addition to existing pnpm lockfile).

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[sarv-tech]

Hi @abhishek-nexgen-dev ,

This PR improves the TypeScript type safety of the cn utility while preserving its existing runtime behavior.

What's Included

• Replaced permissive type structures with stricter TypeScript definitions.

• Added comprehensive unit tests covering edge cases such as:

  • null
  • undefined
  • conditional booleans
  • numbers
  • nested arrays
  • conditional class objects

• Improved developer documentation with detailed JSDoc comments.

• Updated test configuration required for the new test suite.

Verification

• All new cn utility tests pass locally.
• Existing project tests continue to pass.
• No breaking runtime changes were introduced.
• Backward compatibility has been maintained.

This PR is intentionally scoped to the issue requirements and focuses only on improving type safety, test coverage, and maintainability of the cn utility.

Thank you for your review and feedback!
close #10