Introduce comment-to-code ratio check

.github/workflows/c2c-ratio-pr.yml

@@ -0,0 +1,51 @@
+name: Comment-to-code (C2C) ratio
+
+on:
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: >-
+    ${{ github.ref != 'refs/heads/master' &&
+        github.event_name != 'merge_group' &&
+        !startsWith(github.ref, 'refs/heads/gh-readonly-queue') }}
+
+permissions:
+  contents: read
+
+jobs:
+  comment-to-code-ratio:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Install cloc
+        run: npm install --global cloc
+
+      - name: Generate report
+        continue-on-error: true
+        uses: deep5050/comment-to-code-ratio-action@v1.0.1
+        with:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          issue_number: ${{ github.event.pull_request.number }}
+          options: >-
+            --quiet
+            --git
+            --diff
+            ${{ github.event.pull_request.base.sha }}
+            ${{ github.event.pull_request.head.sha }}
+            --md
+            --out=report.md
+            --exclude-dir=.git,3rdparty,build
+
+      - name: Check ratio
+        id: ratio
+        run: python3 scripts/check_comment_to_code_ratio.py report.md --limit 10
+
+      - name: Print final percentage
+        if: always()
+        run: |
+          echo "Comment percentage for PR changes: ${{ steps.ratio.outputs.comment_percentage || 'N/A' }}%"

scripts/check_comment_to_code_ratio.py

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+import argparse
+import os
+import sys
+from pathlib import Path
+
+EXPECTED_HEADER_SUFFIX = [
+    "== files",
+    "!= files",
+    "+ files",
+    "- files",
+    "== blank",
+    "!= blank",
+    "+ blank",
+    "- blank",
+    "== comment",
+    "!= comment",
+    "+ comment",
+    "- comment",
+    "== code",
+    "!= code",
+    "+ code",
+    "- code",
+]
+# Zero-based indices in `cloc --diff --md` rows after splitting by `|`.
+COMMENT_COLUMN_INDICES = (10, 11, 12)
+CODE_COLUMN_INDICES = (14, 15, 16)
+
+
+def parse_changed_totals(report_path):
+    changed_comments = 0
+    changed_code = 0
+    header_found = False
+
+    for raw_line in report_path.read_text(encoding="utf-8").splitlines():
+        if "|" not in raw_line:
+            continue
+
+        cells = [cell.strip() for cell in raw_line.split("|")]
+        if cells and cells[-1] == "":
+            cells = cells[:-1]
+
+        if cells and cells[0] in {"Language", "File"}:
+            if cells[1:] != EXPECTED_HEADER_SUFFIX:
+                sys.exit("Unexpected cloc diff table format.")
+            header_found = True
+            continue
+
+        if not cells:
+            continue
+        if cells[0].startswith((":", "-", "SUM:")):
+            continue
+        if not header_found:
+            continue
+
+        try:
+            changed_comments += sum(
+                int(cells[index]) for index in COMMENT_COLUMN_INDICES
+            )
+            changed_code += sum(int(cells[index]) for index in CODE_COLUMN_INDICES)
+        except (IndexError, ValueError):
+            continue
+
+    if not header_found:
+        print("Unable to find cloc diff table header in report.")
+        sys.exit(1)
+
+    return changed_comments, changed_code
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("report")
+    parser.add_argument("--limit", type=float, default=10.0)
+    args = parser.parse_args()
+
+    report_path = Path(args.report)
+    if not report_path.exists():
+        print(f"{report_path} was not generated by the comment ratio action.")
+        sys.exit(1)
+
+    changed_comments, changed_code = parse_changed_totals(report_path)
+    total_changed_nonblank = changed_comments + changed_code
+    comment_percentage = (
+        0.0
+        if total_changed_nonblank == 0
+        else changed_comments * 100.0 / total_changed_nonblank
+    )
+
+    print(f"Comment percentage for PR changes: {comment_percentage:.2f}%")
+
+    github_output = os.getenv("GITHUB_OUTPUT")
+    if github_output:
+        with Path(github_output).open("a", encoding="utf-8") as output:
+            output.write(f"changed_comments={changed_comments}\n")
+            output.write(f"changed_code={changed_code}\n")
+            output.write(f"comment_percentage={comment_percentage:.2f}\n")
+
+    if comment_percentage > args.limit:
+        print(
+            f"Comment percentage for PR changes is {comment_percentage:.2f}%, "
+            f"which exceeds {args.limit:.2f}%.",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+
+if __name__ == "__main__":
+    main()