fix: guard non-scientific formatter against positive-exp int224 overflow

[thedavidmeister]

Summary

• _toNonScientific accepted floats with exponent > 0 and emitted integer strings whose value exceeded int224.max (e.g. (1, 77) → "100…0" with 78 digits), causing parseDecimalFloat to fail with ParseDecimalPrecisionLoss instead of round-tripping.
• Root cause: the previous guard used an int256-based digit count (76) rather than checking the actual value against int224.max (≈1.34e67).
• Fix: when exponent > 0, revert UnformatableExponent if absCoef > floor(int224.max / 10^exponent). For exponent ≥ 68 the check short-circuits immediately (10^68 > int224.max unconditionally).
• Three pre-existing tests that asserted old non-round-trippable behavior (LargePositiveExponent, LargeCoefficientLargeExponent, OutputShape) are updated to either expect the new revert or bound inputs to the safe range.
• New fuzz test testFormatParseRoundTripNonScientificSafePosExp mirrors the formatter guard in vm.assume and confirms round-trip holds for every accepted positive-exponent float.

Closes #184

Test plan

• forge test --match-path test/src/lib/format/LibFormatDecimalFloat.toDecimalString.t.sol — all 26 pass
• Full forge test suite passes (no regressions)
• Confirm testFormatNonScientificLargePositiveExponent and testFormatNonScientificLargeCoefficientLargeExponent now test vm.expectRevert not success
• Confirm testFormatNonScientificAtIntDigitBoundary with (1, 67) round-trips (1e67 < int224.max ≈ 1.34e67)

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Enhanced decimal formatting validation to prevent overflow when handling large positive exponents; formatter now rejects inputs that exceed representable bounds.

• Tests

  • Strengthened test coverage for decimal formatting boundary conditions with improved revert scenario validation and round-trip parsing verification.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 5788a827-d938-4c1f-8639-69be23c3b0fa

📥 Commits

Reviewing files that changed from the base of the PR and between 356aecf and dd6ad63.

📒 Files selected for processing (4)

• crates/float/abi/DecimalFloat.json
• src/lib/deploy/LibDecimalFloatDeploy.sol
• src/lib/format/LibFormatDecimalFloat.sol
• test/src/lib/format/LibFormatDecimalFloat.toDecimalString.t.sol

Walkthrough

Adds an overflow guard to LibFormatDecimalFloat._toNonScientific that reverts with UnformatableExponent when a positive exponent would produce a decimal string too large for the parser to reconstruct losslessly. The corresponding test suite is updated to expect these reverts instead of successful string outputs.

Changes

Non-scientific positive-exponent overflow guard

Layer / File(s)	Summary
Overflow guard in _toNonScientific src/lib/format/LibFormatDecimalFloat.sol	Adds an exponent > 0 branch that reverts with UnformatableExponent(exponent) immediately for exponent >= 68, and for smaller positive exponents computes limit = int224.max / 10^exponent and reverts when absCoef exceeds that limit.
Test suite alignment with revert behavior test/src/lib/format/LibFormatDecimalFloat.toDecimalString.t.sol	Updates the fuzz comment to document positive-exponent revert conditions; replaces the positive-cap boundary success test with a revert-expectation test; replaces the broad full-range fuzz with constrained tests for non-positive exponents, fixed revert/round-trip cases at exponent boundaries 68 and 67, and a safe positive-exponent fuzz with vm.assume guards; narrows the output-shape fuzz to [-cap, 0]; changes two large positive-exponent tests from string-validation to UnformatableExponent revert assertions.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding an overflow guard in the non-scientific formatter for positive exponents against int224 limits.
Linked Issues check	✅ Passed	The PR fully implements issue #184's fix direction (1): adding precise value checks in _toNonScientific to revert when absCoef exceeds int224.max / 10^exponent, with comprehensive test coverage.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the positive-exponent overflow issue in non-scientific formatting and its corresponding tests; no unrelated modifications present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 2026-06-17-issue-184-nonscientific-positive-exp

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[thedavidmeister]

human-approved; merging (all failing checks are testProdDeployment* deploy-pinned tests — DecimalFloat not yet deployed on live networks, known pre-existing env condition)

[github-actions]

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