fix: scale price ratio correctly when fee token decimals exceed 18

[curryxbo]

calculatePriceRatioWithInfo computed the decimal adjustment as int64(18 - tokenDecimals). Because tokenDecimals is a uint8, the subtraction happened in uint8 space first: a 24-decimal token wrapped to 250, so the ratio was scaled by 1e250 and calculateTokenAmount would charge essentially no gas in that token.

That wrapped ratio is worse than a revenue leak. AltToEth is what caps the gas allowance in eth_estimateGas / eth_call. With ratio ≈ 2e250, a dust token balance converts into an astronomically large ETH budget, while EthToAlt at execution charges ceil(...) = 1 base unit. A 24-decimal fee token could therefore buy unbounded gas for ~zero fee (a block-filling DoS), not only undercharge.

Subtracting as int64 fixes the wrap but leaves a second problem: big.Int.Exp returns 1 for a negative exponent, so a token with more than 18 decimals would silently get no adjustment at all (ratio too large by 10^(decimals-18)). The exponent is now applied in the right direction — multiply by 10^(18-decimals) when the exponent is non-negative, divide by 10^(decimals-18) when it is negative.

No contract or L2-node change: registration of tokens with more than 18 decimals stays allowed, and the node treats priceRatio as an opaque integer. The oracle is the single source of truth.

TestCalculatePriceRatioScalesDownDecimalsAbove18 covers a 24-decimal token and asserts the exact expected ratio, which fails on both the wrapped-exponent and the exponent-ignored behaviour.

This PR also adds .github/workflows/token-price-oracle.yml (make build / make test, Go 1.24) so that regression actually runs in CI. The module previously had no workflow; other Go modules already do. Paths filter uses .yml (not the .yaml typo in gas-oracle.yml).

Summary by CodeRabbit

• Bug Fixes

  • Token price calculations now support tokens with more than 18 decimals, including correct scaling for 24-decimal tokens.

• Tests

  • Added coverage verifying high-decimal token price calculations.

• Chores

  • Added automated build and test checks for token price oracle changes.

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📝 Walkthrough

Walkthrough

The change rejects tokens with more than 18 decimals during registry operations and price ratio calculation. It adds a registry error, signed decimal arithmetic, and regression tests for 24-decimal tokens.

Changes

Token decimal validation

Layer / File(s)	Summary
Registry decimal validation contracts/contracts/l2/system/IL2TokenRegistry.sol, contracts/contracts/l2/system/L2TokenRegistry.sol, contracts/contracts/test/L2TokenRegistry.t.sol	The registry declares UnsupportedTokenDecimals() and reverts during registration or token updates when decimals exceed 18. Tests cover both paths with 24-decimal tokens.
Price updater decimal validation token-price-oracle/updater/token_price.go, token-price-oracle/updater/token_price_test.go	The price updater rejects decimals above 18 before exponent calculation and uses signed arithmetic. A regression test checks the returned error.

Priority: ⬇️ Low

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

Suggested reviewers: dylancai9

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 …	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: correcting price-ratio scaling when fee-token decimals exceed 18.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 unsupported.)

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• Commit unit tests in branch fix/token-decimals-validation

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Actionable comments posted: 2

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Inline comments:
In @.github/workflows/token-price-oracle.yml:
- Line 26: Update the checkout step using actions/checkout to the supported v4
release so the workflow runs on the Node 20 runtime; leave the surrounding build
and test steps unchanged.
- Line 26: Update the actions/checkout step in the workflow to set
persist-credentials to false, preserving the existing checkout behavior and
avoiding token persistence for pull-request-controlled builds and tests.

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📒 Files selected for processing (3)

• .github/workflows/token-price-oracle.yml
• token-price-oracle/updater/token_price.go
• token-price-oracle/updater/token_price_test.go

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