add PR title validation in CI

Author: allnes

.github/PULL_REQUEST_TEMPLATE/task_submission_en.md

@@ -1,3 +1,7 @@
+PR Title (CI enforced):
+- Tasks: `[TASK] <Task>-<Variant>. <Last Name> <First Name> <Middle Name>. <Group>. <Task name>.`
+- Development: `[DEV] <any descriptive title>`
+
 <!--
 Pull request title requirement:
 

.github/PULL_REQUEST_TEMPLATE/task_submission_ru.md

@@ -1,3 +1,7 @@
+Формат заголовка PR (CI):
+- Задачи: `[TASK] <Task>-<Variant>. <Фамилия> <Имя> <Отчество>. <Группа>. <Название задачи>.`
+- Разработка: `[DEV] <произвольное осмысленное название>`
+
 <!--
 Требования к названию pull request:
 

.github/pull_request_template.md

@@ -1,3 +1,7 @@
+PR Title (CI enforced):
+- Tasks: `[TASK] <Task>-<Variant>. <Last Name> <First Name> <Middle Name>. <Group>. <Task name>.`
+- Development: `[DEV] <any descriptive title>`
+
 <!-- Solution for PR template choice: https://stackoverflow.com/a/75030350/24543008 -->
 
 Please go to the `Preview` tab and select the appropriate template:

.github/scripts/validate_pr.py

@@ -0,0 +1,115 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+"""
+Minimal PR title validator for CI gate.
+
+Rules:
+- Accept either a strict task title with required prefix '[TASK]'
+  Pattern: [TASK] <Task>-<Variant>. <Last> <First> <Middle>. <Group>. <Task name>
+- Or a development title with prefix '[DEV]' followed by any non-empty text
+  Pattern: [DEV] <any text>
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import re
+import sys
+from typing import List, Optional
+
+
+TITLE_TASK_REGEX = r"""
+^\[TASK\]\s+
+(?P<task>\d+)-(?P<variant>\d+)\.\s+
+(?P<lastname>[А-ЯA-ZЁ][а-яa-zё]+)\s+
+(?P<firstname>[А-ЯA-ZЁ][а-яa-zё]+)\s+
+(?P<middlename>[А-ЯA-ZЁ][а-яa-zё]+)\.\s+
+(?P<group>.+?)\.\s+
+(?P<taskname>\S.*)
+$
+"""
+
+TITLE_DEV_REGEX = r"^\[DEV\]\s+\S.*$"
+
+
+def _trim(s: Optional[str]) -> str:
+    return (s or "").strip()
+
+
+def validate_title(title: str) -> List[str]:
+    """Validate PR title. Returns a list of error messages (empty if valid)."""
+    title = (title or "").strip()
+    if not title:
+        return [
+            "Empty PR title. Use '[TASK] …' for tasks or '[DEV] …' for development.",
+        ]
+
+    # Accept development titles with a simple rule
+    if re.match(TITLE_DEV_REGEX, title, flags=re.UNICODE):
+        return []
+
+    # Accept strict course task titles
+    if re.match(TITLE_TASK_REGEX, title, flags=re.UNICODE | re.VERBOSE):
+        return []
+
+    example_task_ru = (
+        "[TASK] 2-12. Иванов Иван Иванович. 2341-а234. Вычисление суммы элементов вектора."
+    )
+    example_task_en = (
+        "[TASK] 2-12. Ivanov Ivan Ivanovich. 2341-a234. Vector elements sum calculation."
+    )
+    example_dev = "[DEV] Update docs for lab 2"
+    return [
+        "Invalid PR title.",
+        "Allowed formats:",
+        f"- Task: {example_task_ru}",
+        f"- Task: {example_task_en}",
+        f"- Dev:  {example_dev}",
+    ]
+
+
+def _load_event_payload(path: Optional[str]) -> Optional[dict]:
+    if not path or not os.path.exists(path):
+        return None
+    with open(path, "r", encoding="utf-8") as f:
+        try:
+            return json.load(f)
+        except Exception:
+            return None
+
+
+def main() -> int:
+    try:
+        payload = _load_event_payload(os.environ.get("GITHUB_EVENT_PATH"))
+
+        pr_title = None
+        if payload and payload.get("pull_request"):
+            pr = payload["pull_request"]
+            pr_title = pr.get("title")
+
+        if pr_title is None:
+            # Not a PR context – do not fail the gate
+            print("No PR title in event payload; skipping title check (non-PR event).")
+            return 0
+
+        errs = validate_title(pr_title)
+        if errs:
+            for e in errs:
+                print(f"✗ {e}")
+            return 1
+
+        print("OK: PR title is valid.")
+        return 0
+
+    except SystemExit:
+        raise
+    except Exception as e:
+        print(f"Internal error occurred: {e}", file=sys.stderr)
+        return 2
+
+
+if __name__ == "__main__":
+    sys.exit(main())

.github/workflows/main.yml

@@ -16,7 +16,31 @@ concurrency:
         !startsWith(github.ref, 'refs/heads/gh-readonly-queue') }}
 
 jobs:
+  pr_title:
+    name: PR Title Gate
+    runs-on: ubuntu-latest
+    steps:
+      - name: Non-PR event — skip title validation
+        if: ${{ github.event_name != 'pull_request' }}
+        run: echo "Not a PR event; skipping title check"
+
+      - name: Checkout
+        if: ${{ github.event_name == 'pull_request' }}
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        if: ${{ github.event_name == 'pull_request' }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Validate PR title
+        if: ${{ github.event_name == 'pull_request' }}
+        run: python .github/scripts/validate_pr.py
+
   pre-commit:
+    needs:
+      - pr_title
     uses: ./.github/workflows/pre-commit.yml
   ubuntu:
     needs: