Add nil-element validation for Collection transactions in ChunkDataPack

[zhangchiqing]

Add nil-element validation for [Collection.Transactions] in the [ChunkDataPack] constructor, rejecting CBOR-decoded null transaction elements.

This PR depends on #8689 (and transitively on #8688). It is part of a PR stack that splits up #8668.

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Summary by CodeRabbit

• Bug Fixes
  • Invalid collection data is now rejected when processing chunk data.
  • Clear validation errors are returned for collections containing invalid transactions.
  • Valid collections are checked before being included in processed chunk data.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: cae0efa4-67b3-4ebb-8eca-787979669137

📥 Commits

Reviewing files that changed from the base of the PR and between e46fddf and 257b32f.

📒 Files selected for processing (2)

• model/flow/chunk.go
• model/flow/chunk_test.go

Included review availability: Your plan provides up to 4 included reviews per hour; 2 remain after this review.

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📝 Walkthrough

Walkthrough

NewChunkDataPack now validates non-nil collections before storing them. Invalid collections return a wrapped error. A test covers a collection containing a nil transaction.

Changes

Chunk data pack validation

Layer / File(s)	Summary
Collection reconstruction and validation model/flow/chunk.go, model/flow/chunk_test.go	NewChunkDataPack reconstructs non-nil collections through NewCollection. It preserves nil collections, wraps validation errors with "invalid collection: %w", and returns no pack for invalid input. The test covers a nil transaction entry.

Priority: ⬇️ Low

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

Change: Bug fix

Suggested reviewers: tim-barry

Merge Risk: ⚪ Minimal · up to 543fe

The constructor now validates collections and rejects nil transactions with test coverage; no merge-blocking behavior is established.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files.
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.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding nil-element validation for Collection transactions in the ChunkDataPack constructor.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch leo/nil-validation-chunk-data-pack

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[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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