fix(tracing): return empty arrays for blocks without EVM transactions

[Ri-go]

Summary

• initialize block trace results as a non-nil empty slice when a block has no Ethereum transactions
• preserve virtual transaction alignment while ensuring empty results serialize as [] instead of null
• cover both completely empty blocks and Cosmos-only blocks with no Ethereum messages

Rationale

Injective chain initializes empty block trace results as a non-nil slice, so its JSON response is []. The v1.4.3 gateway alignment path started from a nil slice and returned null when there were no visible transaction hashes. This restores chain-compatible output without changing the v1.4.3 transaction hash and alignment behavior.

Testing

• go test ./internal/evm/rpc/backend -run "TestTraceBlockWithoutEthereumTransactionsReturnsEmptyArray|TestAlignTraceBlockResultsWithVisibleTransactions|TestTraceBlockLatestSendsResolvedBlockContextHeight" -count=1
• go test ./...

Summary by CodeRabbit

• Bug Fixes
  • Fixed block tracing responses for blocks without Ethereum transactions.
  • Such blocks now return a valid empty array ([]) instead of a null result.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: efc4844c-d4ce-4333-bf4f-48003f190f43

📥 Commits

Reviewing files that changed from the base of the PR and between bd53603 and 8dc0737.

📒 Files selected for processing (2)

• internal/evm/rpc/backend/trace_helpers_test.go
• internal/evm/rpc/backend/tracing.go

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📝 Walkthrough

Walkthrough

TraceBlock now returns an empty non-nil trace slice when blocks contain no Ethereum transactions. Tests cover both empty blocks and blocks containing non-Ethereum transactions, asserting the serialized result is [].

Changes

TraceBlock empty results

Layer / File(s)	Summary
Empty-result handling and validation internal/evm/rpc/backend/tracing.go, internal/evm/rpc/backend/trace_helpers_test.go	TraceBlock uses an empty slice for zero Ethereum transactions, with tests confirming the result is non-nil and serializes to [] for both covered block cases.

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

Possibly related PRs

• InjectiveLabs/evm-gateway#7: Adds related TraceBlock unit coverage for replay, ordering, and decoding error handling.

Suggested reviewers: maxim-inj

🚥 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 clearly matches the main change: tracing now returns empty arrays for blocks without EVM transactions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/fix-empty-trace-array

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[Ri-go]

Closing in favor of a smaller replacement PR.