feat(hooks): PR-W5 file-length Stop gate — comment-lint --check-modified-files batch mode + [file_length_gate] opt-in

[aloekun]

概要

file-length-enforcement-plan.md の PR-W5 (Phase 2 / Stop hook gate C)。Phase 1 (PR-W1〜W4、#220/#224/#230/#231) で 800 行以下に整えた clean state を恒久維持する強制層を追加する。

hooks-post-tool-comment-lint-rust に --check-modified-files batch mode を追加し、Stop hook quality_gate の 1 step として PR 範囲 (base..@) の .rs file 行数を検査。800 行超が 1 件でもあれば exit 1 で Stop を block する (Option C-2)。

mechanical な feature 追加、behavior 不変。既存 lint (comment/function/file_length/metrics) は不変。

実装

• src/hooks-post-tool-comment-lint-rust/src/modified_files_check.rs (新規、17 tests)
• main.rs に --check-modified-files dispatch 追加、Cargo.toml に toml 依存追加
• .claude/hooks-config.toml に file-length step + [file_length_gate] section (dogfood のため enabled=true)
• docs/file-length-enforcement-plan.md PR-W5 実績反映

なお本 PR には前セッションの feedback docs コミット (順位 246、todo-summary/todo13) を 別コミットとして bundle している。

ADR-039 3 点セット

• Config opt-in (default OFF): gate_enabled() が unwrap_or(false)。本 repo のみ dogfood で enabled=true
• Kill-switch: 下表
• Bounded lifetime: plan doc 削除条件 3 (override 未使用で 1-2 セッション通過)

Kill-switch table

起動経路	停止コマンド	影響範囲
[file_length_gate] enabled=true + file-length step	enabled=false (恒久)	Stop hook の file-length 判定のみ
Stop 発火時に file-length step 実行	env FILE_LENGTH_CHECK_OVERRIDE=1 (緊急、truthy)	当該 Stop の判定を skip

設計判断

• jj 変更検出は base branch を config 引数化 (default master、ADR-021 § Revset Composability — custom lint NO_HARDCODED_JJ_REVSET_RANGE 指摘対応)
• cmd path は cmd.exe の forward-slash 非対応のため backslash TOML literal string
• jj 失敗時は fail-closed で block (ADR-043、stop_hook_active retry-skip が永続 lock を防止)
• templates (TS/Python) は Rust 非対象のため未追加

検証

• cargo test -p hooks-post-tool-comment-lint-rust: 116 pass / clippy clean / fmt clean
• cargo test --workspace: regression なし / cargo clippy --workspace clean
• dogfood (deploy 済 exe): clean=exit0 / 850行file=block / OVERRIDE(=1,=true)=bypass / enabled=false=no-op / self-host=exit0

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • 大きな Rust ファイルの変更を検出して、一定行数を超える場合に停止条件を満たさないようになりました。
  • 設定によりこのチェックを有効/無効に切り替えられるようになり、緊急時に回避する仕組みも追加されました。
  • 変更検知が不完全な場合は安全側に倒して処理を止めるようになりました。

• Documentation

  • 実装状況と運用方針、完了条件、関連タスクの進捗を更新しました。

[coderabbitai]

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Configuration used: Organization UI

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Run ID: 0dfd3d59-d122-4286-8ff5-dcf2df77c019

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Reviewing files that changed from the base of the PR and between c1d7f38 and 5cc827d.

📒 Files selected for processing (1)

• src/hooks-post-tool-comment-lint-rust/src/modified_files_check.rs

👮 Files not reviewed due to content moderation or server errors (1)

• src/hooks-post-tool-comment-lint-rust/src/modified_files_check.rs

---

📝 Walkthrough

🚥 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	変更内容の中心である file-length の Stop ゲート追加と --check-modified-files/[file_length_gate] の導入を適切に要約しています。
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.

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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 `@src/hooks-post-tool-comment-lint-rust/src/modified_files_check.rs`:
- Around line 176-185: collect_oversize_files currently treats every
read_to_string failure as a skipped file via .ok()?; update it to fail-closed
for existing .rs files by distinguishing missing-file cases from other read
errors. Keep skipping only genuinely deleted/missing paths, and propagate
permission/encoding/race read failures as Err so run_check_modified_files() can
exit 1; use collect_oversize_files and its caller in run_check_modified_files()
to locate the change.

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Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
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ℹ️ Review info

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Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 211e17d5-9c8b-44b6-9ac3-bb3b92cac857

📥 Commits

Reviewing files that changed from the base of the PR and between 125259b and c1d7f38.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (7)

• .claude/hooks-config.toml
• docs/file-length-enforcement-plan.md
• docs/todo-summary.md
• docs/todo13.md
• src/hooks-post-tool-comment-lint-rust/Cargo.toml
• src/hooks-post-tool-comment-lint-rust/src/main.rs
• src/hooks-post-tool-comment-lint-rust/src/modified_files_check.rs

[aloekun]

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