Maintenance: VimScript Variables - Convert to objects and improve documentation

[claude]

Summary

• Converted HighLightVariable and RegisterVariable from classes to object singletons
• Added comprehensive KDoc documentation to both variables
• Updated VimVariableServiceBase to use direct object references instead of instantiation

Area Inspected

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/vimscript/model/variables/HighLightVariable.kt and related Variable implementations

Issues Found

1. Inconsistent singleton pattern: HighLightVariable and RegisterVariable were classes but had no mutable state, yet were being instantiated on every use
2. Missing documentation: HighLightVariable lacked KDoc comments explaining its purpose
3. Wasteful instantiation: VimVariableServiceBase created new instances with HighLightVariable() and RegisterVariable() on every evaluation

Changes Made

1. Convert HighLightVariable to object and add documentation

• Changed from class to internal object since it has no state
• Added comprehensive KDoc explaining what v:hlsearch represents, its behavior, and reference to :help v:hlsearch
• Aligns with the pattern used by KeyVariable and ValueVariable

2. Convert RegisterVariable to object and improve documentation

• Changed from class to internal object for consistency
• Enhanced KDoc to explicitly mention v:register and added reference to :help v:register
• Maintains existing functionality while eliminating unnecessary instantiation

3. Update VimVariableServiceBase to use object references

• Changed from HighLightVariable().evaluate(...) to HighLightVariable.evaluate(...)
• Changed from RegisterVariable().evaluate(...) to RegisterVariable.evaluate(...)
• Matches the pattern already used for KeyVariable and ValueVariable

Why These Changes Improve the Code

1. Performance: Eliminates unnecessary object allocation on every variable evaluation
2. Consistency: All Variable implementations now follow the same pattern - objects for stateless variables, objects with mutable state for stateful ones
3. Maintainability: Better documentation helps future contributors understand what these variables represent
4. Kotlin best practices: Using objects for stateless implementations is idiomatic Kotlin

Testing

Existing tests in HighLightVariableTest and RegisterVariableTest should continue to pass unchanged. The functionality remains identical - only the implementation pattern changed.

🤖 Generated with Claude Code