Documentation: Clarify that #[transactional] is NOT applied by default to functions

[Copilot]

This PR addresses a misconception about the #[transactional] attribute usage in Bifrost pallets by providing comprehensive analysis and documentation.

Issue

Someone claimed that "all functions now have #[transactional] by default" which needed verification and clarification.

Analysis Results

After thorough analysis of the Bifrost codebase, this claim is completely FALSE. The evidence shows:

Key Findings

• 0 out of 17 SLPX pallet call functions (user-facing extrinsics) use #[transactional]
• 0 Farming pallet functions use #[transactional]
• 0 Vtoken-minting pallet functions use #[transactional]
• Only 62 functions across the entire codebase use #[transactional] (out of hundreds)
• All #[transactional] usage is on internal helper functions, not user-facing pallet calls

Actual Behavior

// Must be explicitly imported
use frame_support::{
    transactional,  // <-- Explicit import required
};

// Must be explicitly added to specific functions
#[transactional]  // <-- Explicit annotation required
pub fn handle_internal_operation() -> DispatchResult {
    // Only used for functions needing atomic database operations
}

// Regular pallet calls do NOT use it
pub fn mint() -> DispatchResult {  // <-- No #[transactional]
    // Standard user-facing functions
}

Documentation Added

1. Comprehensive Analysis (transactional_analysis.md) - Detailed investigation results
2. Clear Answers (ANSWER_CN.md, ANSWER_EN.md) - Direct responses in Chinese and English
3. Test Scripts (test_transactional_usage.sh, demo_transactional_patterns.sh) - Executable verification tools

Conclusion

The #[transactional] attribute is:

• ✅ Manually applied by developers for specific functions needing atomicity
• ✅ Used selectively for internal helper functions with complex storage operations
• ❌ NOT a default behavior applied to all or most functions
• ❌ NOT used on user-facing pallet call functions

This documentation will help prevent future confusion about Substrate's transactional behavior in the Bifrost ecosystem.

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