chore: add transfer2 close safeguard

[ananas-block]

Summary by CodeRabbit

• Bug Fixes
  • Added validation to prevent closing token accounts that contain non-zero balances, providing additional safeguards against unintended account closure operations.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a runtime validation check to the Solana token closing path that verifies the token account balance is zero before allowing the close operation to proceed. Non-zero balances will trigger a NonNativeHasBalance error, preventing improper account closure.

Changes

Cohort / File(s)	Summary
Balance Verification on Close programs/compressed-token/program/src/compressed_token/transfer2/compression/ctoken/compress_and_close.rs	Added zero-balance runtime assertion before token account closure. Borrows account data, parses Token amount, and returns error if balance is non-zero. Includes conditional compilation for Solana-specific imports (AccountInfoTrait, Token).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• fix: compress and close hotpath #2059: Also modifies compress_and_close.rs validation logic, adding presence checks and error handling for compressed outputs in the same closure workflow.

Suggested labels

ai-review

Suggested reviewers

• sergeytimoshin
• SwenSchaeferjohann

Poem

🔐 A guardian check stands sentinel and true,
Before the account closes, balance whispers through—
Zero or bust, the rule now holds so tight,
No phantom coins slip away in the night! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'chore: add transfer2 close safeguard' accurately describes the main change: adding a safety check to prevent closing token accounts with non-zero balances in the transfer2 compression workflow.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 70.00%.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch jorrit/chore-add-compress-and-close-safeguard

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[coderabbitai]

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

programs/compressed-token/program/src/compressed_token/transfer2/compression/ctoken/compress_and_close.rs (1)

28-30: ⚠️ Potential issue | 🟠 Major

Import and use convert_token_error for Token::amount_from_slice failures.

At lines 274-275, Token::amount_from_slice returns a TokenError from the SPL Token interface, but the current code discards it and maps to the generic ProgramError::InvalidAccountData. This breaks the expected ErrorCode contract by losing the SPL Token error information.

Import convert_token_error from the shared module and apply it to the error:

🔧 Fix

 use crate::{
     compressed_token::transfer2::accounts::Transfer2Accounts, shared::convert_program_error,
+    shared::convert_token_error,
 };
 ...
                 let amount = Token::amount_from_slice(&data)
-                    .map_err(|_| ProgramError::InvalidAccountData)?;
+                    .map_err(convert_token_error)?;