fix(revm): validate fee token registration in simulation paths

[panos-xyz]

Closes #181

Summary

Fixes an issue where eth_estimateGas (and eth_call) incorrectly returned 0x5208 (21000) for transactions specifying an unregistered or inactive feeTokenID (e.g. 65535) instead of rejecting them.

Root Cause

In crates/revm/src/handler.rs, validate_and_deduct_token_fee handles simulation paths where cfg.is_fee_charge_disabled() is true. It previously short-circuited at the entry of the function and returned Ok(()), skipping the L2 Token Registry checks (TokenFeeInfo::load_for_caller and token_fee_info.is_active). Upstream reth's is_basic_transfer optimization then executed a trial with MIN_TRANSACTION_GAS (21000), which succeeded and returned 0x5208.

Changes

1. Move L2 Token Registry existence and active checks in validate_and_deduct_token_fee before the is_fee_charge_disabled() short-circuit.
2. In simulation paths, after validating that the token is registered and active, nonce is bumped for calls and execution returns early without deducting token fees.
3. Added unit tests in morph-revm:
   • validate_and_deduct_token_fee_rejects_unregistered_token_in_simulation
   • validate_and_deduct_token_fee_rejects_inactive_token_in_simulation
4. Added end-to-end RPC test in crates/node/tests/it/rpc.rs:
   • estimate_gas_rejects_unregistered_fee_token

Summary by CodeRabbit

• Bug Fixes

  • Gas estimation and transaction simulation now reject unregistered or inactive fee tokens with the appropriate registration error.
  • Both gas estimation and contract calls validate fee-token registration before proceeding.
  • Simulations continue to skip fee deduction and nonce updates while avoiding unnecessary fee-token contract lookups.

• Tests

  • Added coverage for invalid fee-token requests across gas estimation and contract-call simulations.

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Run ID: 9248387f-357f-462a-90f6-3e360552fde2

📥 Commits

Reviewing files that changed from the base of the PR and between a5cc281 and 0a35f7b.

📒 Files selected for processing (3)

• crates/node/tests/it/rpc.rs
• crates/revm/src/handler.rs
• crates/revm/src/token_fee.rs

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📝 Walkthrough

Walkthrough

Simulation paths now validate that fee tokens are registered and active before skipping fee deduction. Unit and RPC integration tests verify rejection of unregistered and inactive tokens.

Changes

Fee token validation

Layer / File(s)	Summary
Simulation token validation crates/revm/src/handler.rs	The fee-charge-disabled return now occurs after token registration and activity checks.
Invalid token test coverage crates/revm/src/handler.rs, crates/node/tests/it/rpc.rs	Tests verify rejection of unregistered token 65535 and inactive token 42, including through eth_estimateGas.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 0a35f

Simulation RPCs now reject unregistered or inactive fee-token IDs before skipping fee deduction, while preserving balance-free simulation behavior for valid tokens. The implementation and coverage support merge readiness.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 59.09% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 22 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: validating fee-token registration during simulation paths.
Linked Issues check	✅ Passed	The PR satisfies issue #181. Simulation paths validate that fee tokens are registered and active before the simulation short-circuit. Tests cover unregistered and inactive tokens for eth_call and eth_…
Out of Scope Changes check	✅ Passed	The changes remain within scope. The token-loading refactor, validation ordering, access-tracking helpers, and tests directly support simulation validation and avoiding fee-token balance queries.

• Fix all pre-merge checks with AI

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/estimate-gas-unregistered-token

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