chore(refactor) - blind pkg

[oleg-ssvlabs]

Summary

Extract two small helpers from EnsureBlinded (in protocol/v2/blockchain/beacon/blind/blind.go) to reduce copy-paste duplication across the Capella/Deneb/Electra/Fulu branches.

Motivation

EnsureBlinded converts a full beacon block to its blinded form per fork. Each of the four fork branches was independently reimplementing:

1. SSZ hash-tree-root computation for the transactions and withdrawals lists. The tx type ([]bellatrix.Transaction) and withdrawal type ([]*capella.Withdrawal) are identical across all four forks, but each branch repeated the same (&utilbellatrix.ExecutionPayloadTransactions{...}).HashTreeRoot() / (&utilcapella.ExecutionPayloadWithdrawals{...}).HashTreeRoot() boilerplate with its own error-wrapping.

2. Construction of a deneb.ExecutionPayloadHeader. Deneb, Electra, and Fulu all use the exact same deneb.ExecutionPayload → deneb.ExecutionPayloadHeader conversion, with the exact same 16 field assignments. A field added to deneb.ExecutionPayloadHeader previously required touching three call sites.

Ticket CQ-5 originally recommended extracting "common blinding logic into a generic helper parameterized by fork version." I'm intentionally not going that far — the four blinded block types (apiv1capella.BlindedBeaconBlock, apiv1deneb.BlindedBeaconBlock, apiv1electra.BlindedBeaconBlock used for both Electra and Fulu) have different body field sets and don't share a Go interface. A unified helper would require reflection or heavily-constrained generics for no readability win, and any future fork that changes the body layout would need to fork the abstraction anyway. The per-fork switch branches stay as-is; only the mechanically duplicated parts are factored out.

Changes

• protocol/v2/blockchain/beacon/blind/blind.go:
  • Introduce computePayloadRoots(txs, withdrawals) (txRoot, wRoot, error) — used by all four fork branches.
  • Introduce buildDenebPayloadHeader(*deneb.ExecutionPayload) (*deneb.ExecutionPayloadHeader, error) — used by Deneb, Electra, and Fulu.
  • Capella branch still constructs its own capella.ExecutionPayloadHeader (different type, no blob fields) but now uses computePayloadRoots for the roots.

Net: 291 → 256 lines. Deneb/Electra/Fulu payload-header construction goes from ~20 lines of field copies each to a single helper call.

Closes https://github.com/ssvlabs/ssv-node-board/issues/560

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.3%. Comparing base (41fab61) to head (c8b9bce).
⚠️ Report is 2 commits behind head on stage.

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[greptile-apps]

Greptile Summary

This PR refactors EnsureBlinded in protocol/v2/blockchain/beacon/blind/blind.go by extracting two helpers — computePayloadRoots (used by all four fork branches) and buildDenebPayloadHeader (used by Deneb, Electra, and Fulu) — to eliminate repeated SSZ root computation and deneb.ExecutionPayloadHeader field-copy boilerplate. The behavior for all forks is preserved identically, and existing tests in blind_test.go cover all four fork paths (Capella, Deneb, Electra, Fulu).

Confidence Score: 5/5

• This PR is safe to merge — it is a pure refactoring with no functional changes and all four fork paths are covered by existing tests.
• Only one file is changed. The extracted helpers (computePayloadRoots and buildDenebPayloadHeader) are small, focused, and called with the same nil-guarded inputs as before. The return values for all fork cases (including FuluBlinded vs ElectraBlinded) are confirmed unchanged against the old code via git show. Existing tests in blind_test.go exercise all four fork branches. No P0 or P1 findings.
• No files require special attention.

Important Files Changed

Filename	Overview
protocol/v2/blockchain/beacon/blind/blind.go	Refactors EnsureBlinded by extracting computePayloadRoots and buildDenebPayloadHeader helpers, reducing 291→256 lines with no functional changes. All fork branches preserved correctly; nil-guard checks remain before each helper call; error messages kept in computePayloadRoots.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[EnsureBlinded] --> B{Already blinded?}
    B -- yes --> C[Return as-is per fork]
    B -- no --> D{Fork version}

    D -- Capella --> E[computePayloadRoots\ntxs, withdrawals]
    E --> F[Build capella.ExecutionPayloadHeader\ninline]
    F --> G[Return CapellaBlinded]

    D -- Deneb --> H[buildDenebPayloadHeader\npayload]
    D -- Electra --> H
    D -- Fulu --> H

    H --> I[computePayloadRoots\ntxs, withdrawals]
    I --> J[Build deneb.ExecutionPayloadHeader]
    J --> K{Fork}
    K -- Deneb --> L[Return DenebBlinded]
    K -- Electra --> M[Return ElectraBlinded]
    K -- Fulu --> N[Return FuluBlinded]

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_{Reviews (1): Last reviewed commit: "Refactor: blind pkg" | Re-trigger Greptile}

[momosh-ssv]

Might be worth adding a nil guard on payload here — all three callers already check before calling, so it's safe today, but a one-liner if payload == nil { return nil, fmt.Errorf("nil execution payload") } would be cheap insurance against future misuse.

[oleg-ssvlabs]

this function is unexported(meaning it is tightly connected to local callers) and all local callers already do nil checks here, here and here, so I think it's OK not the nil guard here