fix: make Writable trait async and remove the write_via_buf bridge function

[hanabi1224]

Summary of changes

Changes introduced in this pull request:

• refactor Writable trait to avoid using write_via_buf to bridge Write and AsyncWrite

Reference issue to close (if applicable)

Closes

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

Summary by CodeRabbit

• Refactor
  • Improved internal data writing operations to enhance system performance and reliability.

[coderabbitai]

Walkthrough

Converts the write trait system from synchronous to asynchronous in the forest index module. Renames Writeable to Writable, converts write_to from a sync method to async, replaces Write with AsyncWrite-based I/O across all implementations, and updates test utilities to use Tokio runtime for async execution.

Changes

Cohort / File(s)

Summary

Async Trait System Refactoring src/db/car/forest/index/mod.rs

Renamed trait Writeable to Writable, converted write_to method signature to async with AsyncWrite + Unpin bounds, updated all trait implementations for Version, Slot, RawSlot, V1Header, and generic &T wrapper, replaced write_u64 with write_u64_le().await for little-endian encoding, adjusted helper functions (written_len) and round-trip tests to accommodate async writes, removed WriteBytesExt import while preserving ReadBytesExt.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

• sudo-shashank
• LesnyRumcajs
• akaladarshi

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 15.38% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main changes: converting the Writable trait to async and removing the write_via_buf bridge function.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch hm/async-writable

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[coderabbitai]

🧹 Nitpick comments (1)

src/db/car/forest/index/mod.rs (1)

759-762: Replace defensive Runtime::new() with existing block_on import to avoid repeated runtime construction in quickcheck test loops.

The round_trip function is called repeatedly in quickcheck property generators; constructing a tokio::runtime::Runtime on each invocation is unnecessary overhead. Since futures::executor::block_on is already imported at line 658 and used successfully elsewhere in the file (lines 670, 697) for the same AsyncWrite pattern with Vec<u8>, the refactor is safe:

-        let serialized =
-            write_to_vec(|v| tokio::runtime::Runtime::new()?.block_on(original.write_to(v)));
+        let serialized = write_to_vec(|v| block_on(original.write_to(v)));

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/db/car/forest/index/mod.rs` around lines 759 - 762, The round_trip helper
currently constructs a new tokio::runtime::Runtime via
Runtime::new()?.block_on(...) for serializing, which is costly in quickcheck
loops; replace that call with the already-imported futures::executor::block_on
to run original.write_to(v) (i.e., change
Runtime::new()?.block_on(original.write_to(v)) to
block_on(original.write_to(v))) in the write_to_vec invocation inside round_trip
so you reuse the existing synchronous executor and avoid repeated runtime
construction.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/db/car/forest/index/mod.rs`:
- Around line 759-762: The round_trip helper currently constructs a new
tokio::runtime::Runtime via Runtime::new()?.block_on(...) for serializing, which
is costly in quickcheck loops; replace that call with the already-imported
futures::executor::block_on to run original.write_to(v) (i.e., change
Runtime::new()?.block_on(original.write_to(v)) to
block_on(original.write_to(v))) in the write_to_vec invocation inside round_trip
so you reuse the existing synchronous executor and avoid repeated runtime
construction.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: ec3bad47-cc2a-4247-acf0-648389b0de13

📥 Commits

Reviewing files that changed from the base of the PR and between 0dea2f2 and f844e5e.

📒 Files selected for processing (1)

• src/db/car/forest/index/mod.rs

[codecov]

Codecov Report

❌ Patch coverage is 45.00000% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.51%. Comparing base (0dea2f2) to head (f844e5e).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/db/car/forest/index/mod.rs	45.00%	2 Missing and 9 partials ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/db/car/forest/index/mod.rs	88.55% <45.00%> (-1.19%)	⬇️

... and 2 files with indirect coverage changes

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