refactor(fork-choice): simplify maybeUpdateBestChildAndDescendant Gloas edge case - #8951
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…as edge case Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Summary of ChangesHello @twoeths, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request refactors the Highlights
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Code Review
This is an excellent refactoring that significantly simplifies the fork-choice logic in maybeUpdateBestChildAndDescendant. By removing the isEmptyVsFullEdgeCase helper and its associated guard, the code now relies on a more natural and easier-to-follow fall-through mechanism for tie-breaking. The addition of explicit isGloasBlock() assertions is a great improvement for robustness, making the code's invariants clear and ensuring it fails loudly if they are violated. The changes make the implementation cleaner and more aligned with the specification. Great work!
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…tChildAndDescendant Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
| * For older blocks: returns node.payloadStatus | ||
| * | ||
| * Note: pre-gloas logic won't reach here. Since it is impossible to have two nodes with same weight and root | ||
| * Note: pre-gloas logic won't reach here. Pre-Gloas blocks have different roots, so they are always resolved by the root tiebreaker before reaching here. |
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| * Note: pre-gloas logic won't reach here. Pre-Gloas blocks have different roots, so they are always resolved by the root tiebreaker before reaching here. | |
| * Note: pre-gloas logic won't reach here. Pre-Gloas blocks have different roots, so they are always resolved by the weight and root tiebreaker before reaching here. |
| // Per spec modified-get_weight (gloas/fork-choice.md#L442): a Gloas EMPTY/FULL block from the | ||
| // previous slot (n-1) has effective weight = 0 regardless of accumulated attestations. | ||
| // The isGloasBlock() guard prevents incorrectly zeroing pre-Gloas FULL blocks, which also have | ||
| // payloadStatus=FULL but must use their actual accumulated weight. |
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I think these comments are very lengthy. I think it should be more concise:
| // Per spec modified-get_weight (gloas/fork-choice.md#L442): a Gloas EMPTY/FULL block from the | |
| // previous slot (n-1) has effective weight = 0 regardless of accumulated attestations. | |
| // The isGloasBlock() guard prevents incorrectly zeroing pre-Gloas FULL blocks, which also have | |
| // payloadStatus=FULL but must use their actual accumulated weight. | |
| // Gloas: nodes from previous slot (n-1) with EMPTY/FULL variant post-gloas have weight hardcoded to 0. |
| const childTiebreaker = this.getPayloadStatusTiebreaker(childNode, currentSlot, proposerBoostRoot); | ||
| // Same effective weight and same root — must be Gloas EMPTY vs FULL from n-1 | ||
| if (!isGloasBlock(childNode)) { | ||
| throw new ProtoArrayError({ |
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I think throwing error here changes our Fulu behaviour.
The current behaviour on unstable is if we have two nodes with same weight and same root, we should do changeToChild:
lodestar/packages/fork-choice/src/protoArray/protoArray.ts
Lines 664 to 669 in 96f78af
I think theoretically two nodes with same weight and same root should not happen, but I am not educated to 100% sure throwing error here wouldn't cause issue.
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I removed it in the latest commit, don't think it will ever change the behaviour of pre-gloas through since 1 node cannot have 2 child nodes with the same root, that's enforced through VariantIndices typing
| }); | ||
| } | ||
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| // Tie-breaker by payload status (EMPTY vs FULL) |
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The comment from L1256 should move to here. .
…escendant Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## nc/epbs-fc #8951 +/- ##
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Coverage 52.37% 52.37%
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Files 848 848
Lines 63047 63047
Branches 4670 4670
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Hits 33020 33020
Misses 29959 29959
Partials 68 68 🚀 New features to boost your workflow:
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Motivation
isEmptyVsFullEdgeCase()is not in the spec — it was an implementation helper that bypassed the standard weight → blockRoot tiebreaking order before callinggetPayloadStatusTiebreaker(). Per spec, pre-Gloas nodes must always be tiebroken by weight first, then blockRoot. The guard was obscuring this and making the code harder to follow.Description
isEmptyVsFullEdgeCase()helper fromProtoArrayisEdgeCaseguard that was short-circuiting weight and blockRoot comparisonsgetPayloadStatusTiebreaker()already have equal weight and equal blockRoot by natural fall-through; that scenario can only arise for Gloas blocks (EMPTY vs FULL variants of the same block)isGloasBlock()assertions before the tiebreaker to make the invariant clear and fail loudly if violatedSpec reference: https://github.com/ethereum/consensus-specs/blob/69a2582d5d62c914b24894bdb65f4bd5d4e49ae4/specs/gloas/fork-choice.md?plain=1#L442
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