feat: add per-PR reviewer leases for parallel review (Closes #407)
Structured PR-thread leases with acquire/heartbeat MCP tools and mutation-time enforcement so reviewers cannot race the same PR queue. Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
This commit is contained in:
Claude Opus 4.8
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"""Per-PR reviewer leases for safe parallel review sessions (#407)."""
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from __future__ import annotations
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import os
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import re
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import uuid
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from datetime import datetime, timedelta, timezone
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from typing import Any
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MARKER = "<!-- mcp-review-lease:v1 -->"
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_FIELD_RE = re.compile(
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r"^\s*([a-z_]+)\s*:\s*(.+?)\s*$",
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re.IGNORECASE | re.MULTILINE,
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)
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_FULL_SHA = re.compile(r"^[0-9a-f]{40}$", re.IGNORECASE)
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_TERMINAL_PHASES = frozenset({"done", "released", "blocked"})
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_ACTIVE_PHASES = frozenset({
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"claimed",
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"validating",
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"approved",
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"request-changes",
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"merging",
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})
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DEFAULT_LEASE_TTL_MINUTES = 120
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STALE_WARNING_MINUTES = 30
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RECLAIMABLE_MINUTES = 60
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_SESSION_LEASE: dict[str, Any] | None = None
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def _parse_timestamp(value: str | None) -> datetime | None:
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if not value:
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return None
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text = value.strip()
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if text.endswith("Z"):
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text = text[:-1] + "+00:00"
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try:
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parsed = datetime.fromisoformat(text)
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except ValueError:
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return None
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if parsed.tzinfo is None:
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return parsed.replace(tzinfo=timezone.utc)
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return parsed.astimezone(timezone.utc)
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def _normalize_sha(value: str | None) -> str | None:
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text = (value or "").strip().lower()
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return text if text and _FULL_SHA.match(text) else None
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def _parse_pr_ref(value: str | None) -> int | None:
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digits = re.sub(r"[^\d]", "", value or "")
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return int(digits) if digits.isdigit() else None
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def new_session_id() -> str:
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return f"{os.getpid()}-{uuid.uuid4().hex[:12]}"
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def format_lease_body(
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*,
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repo: str,
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pr_number: int,
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issue_number: int | None,
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reviewer_identity: str,
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profile: str,
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session_id: str,
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worktree: str,
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phase: str,
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candidate_head: str | None,
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target_branch: str,
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target_branch_sha: str | None,
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last_activity: datetime | None = None,
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expires_at: datetime | None = None,
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blocker: str = "none",
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) -> str:
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now = last_activity or datetime.now(timezone.utc)
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expires = expires_at or (now + timedelta(minutes=DEFAULT_LEASE_TTL_MINUTES))
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last_text = now.astimezone(timezone.utc).replace(microsecond=0).isoformat().replace(
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"+00:00", "Z"
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)
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expires_text = expires.astimezone(timezone.utc).replace(microsecond=0).isoformat().replace(
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"+00:00", "Z"
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)
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issue_text = f"#{issue_number}" if issue_number else "none"
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lines = [
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MARKER,
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f"repo: {repo}",
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f"pr: #{pr_number}",
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f"issue: {issue_text}",
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f"reviewer_identity: {reviewer_identity}",
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f"profile: {profile}",
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f"session_id: {session_id}",
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f"worktree: {worktree}",
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f"phase: {phase}",
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f"candidate_head: {candidate_head or 'none'}",
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f"target_branch: {target_branch}",
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f"target_branch_sha: {target_branch_sha or 'none'}",
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f"last_activity: {last_text}",
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f"expires_at: {expires_text}",
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f"blocker: {blocker}",
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]
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return "\n".join(lines)
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def parse_lease_comment(body: str) -> dict[str, Any] | None:
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text = body or ""
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if MARKER not in text:
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return None
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fields: dict[str, str] = {}
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for match in _FIELD_RE.finditer(text):
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fields[match.group(1).strip().lower()] = match.group(2).strip()
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if not fields:
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return None
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return {
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"repo": fields.get("repo"),
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"pr_number": _parse_pr_ref(fields.get("pr")),
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"issue_number": _parse_pr_ref(fields.get("issue")),
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"reviewer_identity": fields.get("reviewer_identity"),
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"profile": fields.get("profile"),
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"session_id": fields.get("session_id"),
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"worktree": fields.get("worktree"),
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"phase": (fields.get("phase") or "").strip().lower() or None,
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"candidate_head": _normalize_sha(fields.get("candidate_head")),
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"target_branch": fields.get("target_branch"),
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"target_branch_sha": _normalize_sha(fields.get("target_branch_sha")),
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"last_activity": fields.get("last_activity"),
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"expires_at": fields.get("expires_at"),
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"blocker": fields.get("blocker"),
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"raw_fields": fields,
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}
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def _lease_entries(comments: list[dict], *, pr_number: int) -> list[dict]:
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entries: list[dict] = []
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for comment in comments or []:
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parsed = parse_lease_comment(comment.get("body") or "")
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if not parsed:
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continue
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if parsed.get("pr_number") not in (None, pr_number):
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continue
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entries.append({
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**parsed,
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"comment_id": comment.get("id"),
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"author": (comment.get("user") or {}).get("login") or comment.get("author"),
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"created_at": comment.get("created_at"),
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"updated_at": comment.get("updated_at"),
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})
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return entries
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def _lease_expired(lease: dict, *, now: datetime) -> bool:
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expires_at = _parse_timestamp(lease.get("expires_at"))
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return bool(expires_at and expires_at <= now)
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def _minutes_since_activity(lease: dict, *, now: datetime) -> float | None:
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last = _parse_timestamp(lease.get("last_activity"))
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if not last:
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return None
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return (now - last).total_seconds() / 60.0
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def classify_lease_freshness(lease: dict, *, now: datetime | None = None) -> str:
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"""Return active, stale_warning, reclaimable, expired, or terminal."""
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now = now or datetime.now(timezone.utc)
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phase = (lease.get("phase") or "").strip().lower()
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if phase in _TERMINAL_PHASES:
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return "terminal"
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if _lease_expired(lease, now=now):
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return "expired"
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minutes = _minutes_since_activity(lease, now=now)
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if minutes is None:
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return "active"
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if minutes >= RECLAIMABLE_MINUTES:
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return "reclaimable"
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if minutes >= STALE_WARNING_MINUTES:
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return "stale_warning"
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return "active"
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def find_active_reviewer_lease(
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comments: list[dict],
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*,
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pr_number: int,
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now: datetime | None = None,
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) -> dict[str, Any] | None:
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"""Newest non-terminal, unexpired lease for *pr_number*."""
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now = now or datetime.now(timezone.utc)
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for lease in reversed(_lease_entries(comments, pr_number=pr_number)):
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phase = (lease.get("phase") or "").strip().lower()
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if phase in _TERMINAL_PHASES:
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continue
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if _lease_expired(lease, now=now):
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continue
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if phase in _ACTIVE_PHASES or phase:
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lease = dict(lease)
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lease["freshness"] = classify_lease_freshness(lease, now=now)
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return lease
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return None
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def assess_acquire_lease(
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comments: list[dict],
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*,
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pr_number: int,
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reviewer_identity: str,
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profile: str,
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session_id: str,
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repo: str,
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issue_number: int | None,
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worktree: str,
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candidate_head: str | None,
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target_branch: str,
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target_branch_sha: str | None,
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now: datetime | None = None,
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) -> dict[str, Any]:
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"""Fail closed when another session holds an active lease."""
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now = now or datetime.now(timezone.utc)
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reasons: list[str] = []
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existing = find_active_reviewer_lease(comments, pr_number=pr_number, now=now)
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if existing:
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owner_session = (existing.get("session_id") or "").strip()
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freshness = existing.get("freshness") or classify_lease_freshness(existing, now=now)
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if owner_session and owner_session != session_id and freshness in {
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"active", "stale_warning"
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}:
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reasons.append(
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f"PR #{pr_number} already has active reviewer lease "
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f"(session_id={owner_session}, phase={existing.get('phase')})"
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)
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elif owner_session and owner_session != session_id and freshness == "reclaimable":
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reasons.append(
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f"PR #{pr_number} lease is reclaimable but still held by "
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f"session_id={owner_session}; explicit reclaim not implemented "
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"(fail closed)"
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)
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if not (reviewer_identity or "").strip():
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reasons.append("reviewer identity required for lease acquisition")
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if not (session_id or "").strip():
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reasons.append("session_id required for lease acquisition")
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if not (worktree or "").strip():
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reasons.append("worktree path required for lease acquisition")
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allowed = not reasons
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body = None
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if allowed:
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body = format_lease_body(
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repo=repo,
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pr_number=pr_number,
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issue_number=issue_number,
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reviewer_identity=reviewer_identity,
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profile=profile,
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session_id=session_id,
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worktree=worktree,
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phase="claimed",
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candidate_head=candidate_head,
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target_branch=target_branch,
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target_branch_sha=target_branch_sha,
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last_activity=now,
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)
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return {
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"acquire_allowed": allowed,
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"reasons": reasons,
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"existing_lease": existing,
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"lease_body": body,
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"session_id": session_id,
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}
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def record_session_lease(lease: dict[str, Any]) -> dict[str, Any]:
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global _SESSION_LEASE
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_SESSION_LEASE = dict(lease)
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return dict(_SESSION_LEASE)
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def clear_session_lease() -> None:
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global _SESSION_LEASE
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_SESSION_LEASE = None
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def get_session_lease() -> dict[str, Any] | None:
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return dict(_SESSION_LEASE) if _SESSION_LEASE else None
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def assess_mutation_lease_gate(
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*,
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pr_number: int,
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comments: list[dict],
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reviewer_identity: str,
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session_id: str | None,
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mutation: str,
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live_head_sha: str | None,
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pinned_head_sha: str | None,
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now: datetime | None = None,
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) -> dict[str, Any]:
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"""Reviewer mutations require an owned, current PR lease."""
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now = now or datetime.now(timezone.utc)
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reasons: list[str] = []
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session = get_session_lease()
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active = find_active_reviewer_lease(comments, pr_number=pr_number, now=now)
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if not session:
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reasons.append(
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f"no in-session reviewer lease recorded; acquire via "
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f"gitea_acquire_reviewer_pr_lease before {mutation}"
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)
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elif session.get("pr_number") != pr_number:
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reasons.append(
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f"session lease is for PR #{session.get('pr_number')}, not #{pr_number}"
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)
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elif (session.get("session_id") or "") != (session_id or session.get("session_id")):
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reasons.append("session lease session_id mismatch (fail closed)")
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if active:
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owner = (active.get("session_id") or "").strip()
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if owner and session_id and owner != session_id:
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reasons.append(
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f"active PR lease owned by session_id={owner}; current session "
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f"cannot {mutation}"
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)
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pinned = _normalize_sha(pinned_head_sha)
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live = _normalize_sha(live_head_sha)
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lease_head = active.get("candidate_head")
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if pinned and live and pinned != live:
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reasons.append(
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"PR head changed during lease; stop and re-validate before "
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f"reviewer {mutation}"
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)
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if lease_head and live and lease_head != live:
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reasons.append(
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"live PR head differs from lease candidate_head; refresh lease "
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f"before {mutation}"
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)
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freshness = active.get("freshness") or classify_lease_freshness(active, now=now)
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if freshness in {"expired", "reclaimable"}:
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reasons.append(f"reviewer lease freshness is '{freshness}' (fail closed)")
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else:
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reasons.append(f"no active reviewer lease found on PR #{pr_number}")
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allowed = not reasons
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return {
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"mutation_allowed": allowed,
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"block": not allowed,
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"reasons": reasons,
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"active_lease": active,
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"session_lease": session,
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}
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def assess_lease_inventory(
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comments_by_pr: dict[int, list[dict]],
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*,
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now: datetime | None = None,
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) -> dict[str, Any]:
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"""Summarize lease states across PR comment threads."""
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now = now or datetime.now(timezone.utc)
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active: list[dict] = []
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stale: list[dict] = []
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reclaimable: list[dict] = []
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for pr_number, comments in (comments_by_pr or {}).items():
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lease = find_active_reviewer_lease(comments, pr_number=pr_number, now=now)
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if not lease:
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continue
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freshness = lease.get("freshness") or classify_lease_freshness(lease, now=now)
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entry = {"pr_number": pr_number, "session_id": lease.get("session_id"), "freshness": freshness}
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if freshness == "stale_warning":
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stale.append(entry)
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elif freshness == "reclaimable":
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reclaimable.append(entry)
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else:
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active.append(entry)
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return {
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"active_review_leases": active,
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"stale_review_leases": stale,
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"reclaimable_review_leases": reclaimable,
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}
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Reference in New Issue
Block a user