Merge pull request #12019 from KATO-Hiro/#12018

chore: Migrate link checker from mlc to lychee (#12018)

Author: KATO-Hiro

.claude/rules/tools.md

@@ -26,4 +26,5 @@
 
 | Tool | Version | Role | Constraints |
 |---|---|---|---|
-| GitHub Actions | — | Automated link validation | Do not run link checks locally with `curl` or `wget` |
+| lychee | 0.x (via lychee-action) | Automated link validation (GitHub Actions) | Configuration in `lychee.toml`. Do not run link checks locally with `curl` or `wget`. Weekly scheduled scan + PR checks. |
+| lychee-action | v2.8.0 | GitHub Actions integration for lychee | Used in `.github/workflows/` for link checking |

.github/workflows/link_checker.yml

@@ -2,16 +2,22 @@ name: Check Markdown links with scheduled job
 
 on:
   schedule:
-  # Run everyday at 12:30 AM, JST (See https://pubs.opengroup.org/onlinepubs/9699919799/utilities/crontab.html#tag_20_25_07)
-  # See: https://docs.github.com/en/free-pro-team@latest/actions/reference/events-that-trigger-workflows#scheduled-events
-  - cron: "30 15 * * *"
+    - cron: "30 15 * * 2"  # Every Wednesday at 0:30 JST (Tue 15:30 UTC)
 
 jobs:
-  markdown-link-check:
+  lychee:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
-    - uses: gaurav-nelson/github-action-markdown-link-check@v1
-      with:
-        use-quiet-mode: 'yes'
-        use-verbose-mode: 'yes'
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+
+      - name: Restore lychee cache
+        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+        with:
+          path: .lycheecache
+          key: cache-lychee-${{ github.ref }}
+          restore-keys: cache-lychee-
+
+      - uses: lycheeverse/lychee-action@8646ba30535128ac92d33dfc9133794bfdd9b411 # v2.8.0
+        with:
+          args: --cache --max-cache-age 14d --quiet "docs/**/*.md" "monthly_changelog/**/*.md" "README.md" "CONTRIBUTING.md"
+          fail: true

.github/workflows/link_checker_for_modified_files.yml

@@ -3,19 +3,33 @@ name: Check Markdown links for modified files
 on: [pull_request]
 
 jobs:
-  markdown-link-check:
+  lychee:
     runs-on: ubuntu-latest
     steps:
-      - name: Check out Git repository
-        uses: actions/checkout@v6
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+        with:
+          fetch-depth: 0
+
+      - name: Get changed markdown files
+        id: changed-files
+        uses: tj-actions/changed-files@ed68ef82c095e0d48ec87eccea555d944a631a4c # v46.0.5
+        with:
+          files: |
+            docs/**/*.md
+            monthly_changelog/**/*.md
+            README.md
+            CONTRIBUTING.md
+
+      - name: Restore lychee cache
+        if: steps.changed-files.outputs.any_changed == 'true'
+        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+        with:
+          path: .lycheecache
+          key: cache-lychee-${{ github.ref }}
+          restore-keys: cache-lychee-
 
-      # Workaround for `fatal: unsafe repository (REPO is owned by someone else)` issue
-      # https://github.com/actions/checkout/issues/760
-      # https://github.com/actions/checkout/issues/766
-      # https://github.com/gaurav-nelson/github-action-markdown-link-check/issues/132
-      - name: Run markdown-link-check
-        uses: gaurav-nelson/github-action-markdown-link-check@v1
+      - uses: lycheeverse/lychee-action@8646ba30535128ac92d33dfc9133794bfdd9b411 # v2.8.0
+        if: steps.changed-files.outputs.any_changed == 'true'
         with:
-          use-quiet-mode: 'yes'
-          use-verbose-mode: 'yes'
-          check-modified-files-only: 'yes'
+          args: --cache --max-cache-age 14d --quiet ${{ steps.changed-files.outputs.all_changed_files }}
+          fail: true

.gitignore

@@ -119,3 +119,6 @@ __pycache__/
 
 # MkDocs
 site/
+
+# Lychee cache
+.lycheecache

docs/contributing/references.md

@@ -8,12 +8,8 @@ title: 関連プロジェクト・参考資料
 
 - [AtCoderでの競技プログラミングがもっと楽しくなるサイトまとめ](https://noimin.hatenablog.com/entry/2017/12/16/230900)
 
-<!-- markdown-link-check-disable -->
-
 - [AtCoder Wiki](https://wikiwiki.jp/procon/Atcoder)
 
-<!-- markdown-link-check-enable -->
-
 - [Awesome Competitive Programming](https://github.com/lnishan/awesome-competitive-programming) ![GitHub Repo stars](https://img.shields.io/github/stars/lnishan/awesome-competitive-programming?style=plastic)
 
 ## 参考資料
@@ -32,18 +28,14 @@ title: 関連プロジェクト・参考資料
 
 ### GitHub Actions
 
-- [GitHub Action - Markdown link check](https://github.com/gaurav-nelson/github-action-markdown-link-check)
+- [lychee](https://github.com/lycheeverse/lychee) — Fast link checker (Rust)
 
-- [markdown-link-check](https://github.com/tcort/markdown-link-check)
-
-- [TOC Generator](https://github.com/technote-space/toc-generator)
+- [lychee-action](https://github.com/lycheeverse/lychee-action) — GitHub Actions integration
 
 ### UI
 
 - [Favicon Generator - Text to Favicon - favicon.io](https://favicon.io/favicon-generator/)
 
-- [How to add Emoji Prefix to commit message](https://qiita.com/Jung0/items/0a9a7a97a2c17f92d3c5)
-
 - [Summary Card for Twitter](https://developer.twitter.com/en/docs/twitter-for-websites/cards/overview/summary)
 
 - [Card validator](https://cards-dev.twitter.com/validator)

lychee.toml

@@ -0,0 +1,46 @@
+# Lychee link checker configuration
+
+exclude = [
+  # Domains that return 403 / explicitly reject automated access
+  "^https://archive\\.topcoder\\.com/",
+  "^https://atcoder-companions\\.kakira\\.dev/",
+  "^https://atcoder\\.jp/",
+  "^https://beet-aizu\\.hatenablog\\.com/",
+  "^https://cards-dev\\.twitter\\.com/",
+  "^https://clist\\.by/",
+  "^https://codeforces\\.com/",
+  "^https://ctftime\\.org/",
+  "^https://dreamhack\\.io/",
+  "^https://github\\.com/",
+  "^https://img\\.shields\\.io/github/stars/",
+  "^https://kakuyomu\\.jp/",
+  "^https://kenkoooo\\.com/atcoder/",
+  "^https://leetcode\\.com/",
+  "^https://medium\\.com/",
+  "^https://oeis\\.org/",
+  "^https://paiza\\.jp/",
+  "^https://play\\.picoctf\\.org/",
+  "^https://qiita\\.com/",
+  "^https://shindanmaker\\.com/",
+  "^https://solved\\.ac/",
+  "^https://speakerdeck\\.com/",
+  "^https://taksas\\.net/",
+  "^https://twitter\\.com/",
+  "^https://vjudge\\.net/",
+  "^https://www\\.acmicpc\\.net/",
+  "^https://www\\.codechef\\.com/",
+  "^https://www\\.creativ\\.xyz/",
+  "^https://www\\.topcoder\\.com/",
+  "^https://x\\.com/",
+  # Self-hosted site
+  "^https://kato-hiro\\.github\\.io/AtCoderClans/",
+]
+
+# Accept 429 (Rate Limited) in addition to default success codes (100–103, 200–299)
+# Default: 100..=103,200..=299
+accept = ["100..=103", "200..=299", "429"]
+
+max_concurrency = 8
+max_retries = 0
+retry_wait_time = 3
+cache = true