types, rawdb, p2p, stagedsync: distinguish empty BALs

[taratorio]

Follow-up to #22894 addressing the staged-sync review comment and the rawdb review comment.

The original Header.HasBAL() predicate conflated two states: whether the BAL commitment field is present and whether it commits to a non-empty BAL. Those meanings need different behavior for a canonical empty BAL encoded as 0xc0.

This change:

• defines Header.HasBAL() as presence of the BAL commitment field;
• adds Header.HasNonEmptyBAL() for a commitment other than the canonical empty-list hash;
• uses HasNonEmptyBAL() in staged sync and backward BAL fetching to avoid unnecessary database and network work;
• keeps rawdb.ReadBlock on HasBAL() so a stored empty 0xc0 sidecar is preserved;
• covers missing, empty, and non-empty commitments, including the required single DB lookup for a missing non-empty sidecar;
• makes TestAssembleBlockWithFreshlyAddedTxns wait for observed txpool polls instead of a fixed delay.

This keeps block reconstruction faithful while retaining the intended optimization for BAL consumers that do not need an empty sidecar. The builder-test change removes timing dependence and does not change production block-building behavior.

TDD note: the CI stabilization is a test-only synchronization refactor, so no production behavior was changed. The failed race-test job is the original red signal.

Validation:

• go test ./execution/types ./db/rawdb ./execution/stagedsync ./execution/p2p -count=1
• go test ./execution/stagedsync ./execution/execmodule -run '^(TestBlockAccessListBytes|TestAssembleBlockWithFreshlyAddedTxns)$' -count=20
• ERIGON_EXEC3_PARALLEL=true GOMAXPROCS=4 go test -race -timeout=10m ./execution/stagedsync ./execution/execmodule -run '^(TestBlockAccessListBytes|TestAssembleBlockWithFreshlyAddedTxns)$' -count=50
• ERIGON_EXEC3_PARALLEL=true GOMAXPROCS=4 go test -race -timeout=60m ./execution/execmodule -count=3
• go test ./execution/stagedsync ./execution/execmodule -count=1
• make lint (four consecutive clean runs)
• make erigon integration

[Copilot]

Pull request overview

This PR refines Erigon’s EIP-7928 Block Access List (BAL) handling by separating “commitment field is present” from “commitment is non-empty”, allowing empty BAL commitments (canonical 0xc0) to be treated as present while still avoiding unnecessary DB/network work for consumers that only benefit from non-empty BALs.

Changes:

• Redefines Header.HasBAL() to mean “BAL commitment field present” and introduces Header.HasNonEmptyBAL() to mean “commitment is not the canonical empty-list hash”.
• Updates staged sync execution (exec3) and backward downloader BAL request selection to use HasNonEmptyBAL() to skip work for empty commitments.
• Preserves faithful block reconstruction in rawdb.ReadBlock (including stored empty BAL sidecars) and adds regression tests covering missing/empty/non-empty commitment states and call sites.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
execution/types/block.go	Redefines HasBAL() semantics (presence) and adds HasNonEmptyBAL() (non-empty commitment).
execution/types/block_access_list_test.go	Adds tests validating HasBAL() vs HasNonEmptyBAL() behavior for missing/empty/non-empty commitments.
execution/stagedsync/exec3.go	Adds blockAccessListBytes helper and switches exec path to avoid DB reads for empty commitments.
execution/stagedsync/exec3_bal_test.go	Adds tests ensuring stagedsync skips DB reads when BAL field is missing or commitment is empty.
execution/p2p/bbd.go	Skips backward BAL requests for empty commitments by switching to HasNonEmptyBAL().
db/rawdb/accessors_chain.go	Uses header.HasBAL() to ensure empty BAL sidecars are preserved on block reconstruction.
db/rawdb/accessors_chain_test.go	Adds regression test ensuring ReadBlock loads stored empty BAL bytes.

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