fix: Make third-party migration writes an all-or-nothing batch

[hatayama]

Summary

• Replace per-file Write with WriteBatch / WriteBatchAsync so migration apply is one prepare → commit transaction
• Keep .bak sidecars until the full commit succeeds; on mid-batch failure, restore already committed targets and leave no half-migrated project
• Move the async yield cadence into prepare; commit stays rename-only with no yields
• Add focused writer tests for happy path, prepare failure, commit rollback of existing and newly created files, and async yield-sized batches

User Impact

Applying a V2→V3 third-party tool migration no longer leaves the project half-rewritten when a file write fails mid-batch; already written files are restored from backups.

Test plan

• uloop compile — 0 errors / 0 warnings
• uloop run-tests --filter-type regex --filter-value ThirdPartyToolMigrationFileWriterTests — 5/5 passed
• Live demo via uloop execute-dynamic-code + reflection: inject commit failure with a directory target → IOException, file1 restored to original, file3 untouched, sidecarCount=0

Live verification log

tempDirectory=.../UnityCliLoopMigrationWriterLiveDemo/...
exception=IOException: The file '.../FileTwo.cs' already exists.
file1After=original-one
file3After=original-three
file1Restored=True
file3Untouched=True
sidecarCount=0

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 8eab379 and 0ae4edf.

📒 Files selected for processing (1)

• Packages/src/Editor/Infrastructure/ThirdPartyToolMigration/ThirdPartyToolMigrationFileWriter.cs

🚧 Files skipped from review as they are similar to previous changes (1)

• Packages/src/Editor/Infrastructure/ThirdPartyToolMigration/ThirdPartyToolMigrationFileWriter.cs

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📝 Walkthrough

Walkthrough

Migration file updates now use atomic batch writes with temporary files, backups, rollback, and cleanup. Synchronous and asynchronous services delegate to the batch writer, with tests covering success, failures, rollback, sidecar cleanup, and large batches.

Changes

Batch migration writes

Layer / File(s)	Summary
Batch writer and rollback mechanics Packages/src/Editor/Infrastructure/ThirdPartyToolMigration/...	Adds synchronous and asynchronous two-phase batch writing, backup-based rollback, and best-effort sidecar cleanup.
Migration service batch integration Packages/src/Editor/Infrastructure/ThirdPartyToolMigration/ThirdPartyToolMigrationFileService.cs	Replaces per-file mutation loops with synchronous and asynchronous batch writer calls while preserving pre-write cancellation handling.
Atomicity and async validation Assets/Tests/Editor/ThirdPartyToolMigrationFileWriterTests.cs	Tests successful writes, preparation and commit failures, rollback behavior, sidecar cleanup, and asynchronous large-batch commits.

Estimated code review effort: 4 (Complex) | ~45 minutes

Sequence Diagram(s)

sequenceDiagram
  participant MigrationFileService
  participant ThirdPartyToolMigrationFileWriter
  participant FileSystem
  MigrationFileService->>ThirdPartyToolMigrationFileWriter: Submit migration changes
  ThirdPartyToolMigrationFileWriter->>FileSystem: Write temporary sidecars
  ThirdPartyToolMigrationFileWriter->>FileSystem: Commit moves or replacements
  FileSystem-->>ThirdPartyToolMigrationFileWriter: Return commit result
  ThirdPartyToolMigrationFileWriter->>FileSystem: Restore backups or delete new targets on failure
  ThirdPartyToolMigrationFileWriter-->>MigrationFileService: Complete batch or propagate exception

Loading

Possibly related PRs

• hatayama/unity-cli-loop#1396: Both changes modify ThirdPartyToolMigrationFileWriter file operations and sidecar handling.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: making third-party migration writes batch-based and all-or-nothing.
Description check	✅ Passed	The description accurately summarizes the batch transaction, rollback behavior, async changes, and added tests.
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 fix/migration-write-batch-transaction

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In
`@Packages/src/Editor/Infrastructure/ThirdPartyToolMigration/ThirdPartyToolMigrationFileWriter.cs`:
- Around line 90-95: Update PrepareAll and PrepareAllAsync to register each
generated temp sidecar path in preparedWrites before invoking Prepare or
WriteAllText. Ensure cleanup can reach the path when writing fails, while
preserving the existing PreparedWrite flow for successful writes.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 8ddb61f3-c3c3-4625-888d-5d46ed50334e

📥 Commits

Reviewing files that changed from the base of the PR and between 8785326 and 8eab379.

⛔ Files ignored due to path filters (1)

• Assets/Tests/Editor/ThirdPartyToolMigrationFileWriterTests.cs.meta is excluded by none and included by none

📒 Files selected for processing (3)

• Assets/Tests/Editor/ThirdPartyToolMigrationFileWriterTests.cs
• Packages/src/Editor/Infrastructure/ThirdPartyToolMigration/ThirdPartyToolMigrationFileService.cs
• Packages/src/Editor/Infrastructure/ThirdPartyToolMigration/ThirdPartyToolMigrationFileWriter.cs