refactor(db): extract _safe_session/_detach_close to _helpers.py

Module-level session helpers move into sqlmodel_repo/_helpers.py.
__init__.py re-exports them so external import paths
(decnet.web.db.sqlmodel_repo._safe_session) keep resolving.

decnet/web/db/sqlmodel_repo/__init__.py

@@ -62,79 +62,11 @@ from decnet.web.db.models import (
 )
 
 
-from contextlib import asynccontextmanager
+from decnet.web.db.sqlmodel_repo._helpers import (  # noqa: F401  (re-exported for tests/external)
-
+    _safe_session,
-from decnet.logging import get_logger
+    _detach_close,
-
+    _cleanup_tasks,
-_log = get_logger("db.pool")
+)
-
-# Hold strong refs to in-flight cleanup tasks so they aren't GC'd mid-run.
-_cleanup_tasks: set[asyncio.Task] = set()
-
-
-def _detach_close(session: AsyncSession) -> None:
-    """Hand session cleanup to a fresh task so the caller's cancellation
-    doesn't interrupt it.
-
-    ``asyncio.shield`` doesn't help on the exception path: shield prevents
-    *other* tasks from cancelling the inner coroutine, but if the *current*
-    task is already cancelled, its next ``await`` re-raises
-    ``CancelledError`` as soon as the inner coroutine yields.  That's what
-    happens when uvicorn cancels a request mid-query — the rollback inside
-    ``session.close()`` can't complete, and the aiomysql connection is
-    orphaned (pool logs "non-checked-in connection" on GC).
-
-    A fresh task isn't subject to the caller's pending cancellation, so
-    ``close()`` (or the ``invalidate()`` fallback for a dead connection)
-    runs to completion and the pool reclaims the connection promptly.
-
-    Fire-and-forget on purpose: the caller is already unwinding and must
-    not wait on cleanup.
-    """
-    async def _cleanup() -> None:
-        try:
-            await session.close()
-        except BaseException:
-            try:
-                session.sync_session.invalidate()
-            except BaseException:
-                _log.debug("detach-close: invalidate failed", exc_info=True)
-
-    try:
-        loop = asyncio.get_running_loop()
-    except RuntimeError:
-        # No running loop (shutdown path) — best-effort sync invalidate.
-        try:
-            session.sync_session.invalidate()
-        except BaseException:
-            _log.debug("detach-close: no-loop invalidate failed", exc_info=True)
-        return
-    task = loop.create_task(_cleanup())
-    _cleanup_tasks.add(task)
-    # Consume any exception to silence "Task exception was never retrieved".
-    task.add_done_callback(lambda t: (_cleanup_tasks.discard(t), t.exception()))
-
-
-@asynccontextmanager
-async def _safe_session(factory: async_sessionmaker[AsyncSession]):
-    """Session context manager that keeps close() reliable under cancellation.
-
-    Success path: await close() inline so the caller observes cleanup
-    (commit visibility, connection release) before proceeding.
-
-    Exception path (includes CancelledError from client disconnects):
-    detach close() to a fresh task.  The caller is unwinding and its
-    own cancellation would abort an inline close mid-rollback, leaving
-    the aiomysql connection orphaned.
-    """
-    session = factory()
-    try:
-        yield session
-    except BaseException:
-        _detach_close(session)
-        raise
-    else:
-        await session.close()
 
 
 class SQLModelRepository(BaseRepository):

decnet/web/db/sqlmodel_repo/_helpers.py

@@ -0,0 +1,83 @@
+"""Module-level session helpers shared by every repository mixin.
+
+``_safe_session`` and ``_detach_close`` make session cleanup robust under
+client-cancellation. See ``_detach_close`` for the full rationale.
+"""
+from __future__ import annotations
+
+import asyncio
+from contextlib import asynccontextmanager
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from decnet.logging import get_logger
+
+_log = get_logger("db.pool")
+
+# Hold strong refs to in-flight cleanup tasks so they aren't GC'd mid-run.
+_cleanup_tasks: set[asyncio.Task] = set()
+
+
+def _detach_close(session: AsyncSession) -> None:
+    """Hand session cleanup to a fresh task so the caller's cancellation
+    doesn't interrupt it.
+
+    ``asyncio.shield`` doesn't help on the exception path: shield prevents
+    *other* tasks from cancelling the inner coroutine, but if the *current*
+    task is already cancelled, its next ``await`` re-raises
+    ``CancelledError`` as soon as the inner coroutine yields.  That's what
+    happens when uvicorn cancels a request mid-query — the rollback inside
+    ``session.close()`` can't complete, and the aiomysql connection is
+    orphaned (pool logs "non-checked-in connection" on GC).
+
+    A fresh task isn't subject to the caller's pending cancellation, so
+    ``close()`` (or the ``invalidate()`` fallback for a dead connection)
+    runs to completion and the pool reclaims the connection promptly.
+
+    Fire-and-forget on purpose: the caller is already unwinding and must
+    not wait on cleanup.
+    """
+    async def _cleanup() -> None:
+        try:
+            await session.close()
+        except BaseException:
+            try:
+                session.sync_session.invalidate()
+            except BaseException:
+                _log.debug("detach-close: invalidate failed", exc_info=True)
+
+    try:
+        loop = asyncio.get_running_loop()
+    except RuntimeError:
+        # No running loop (shutdown path) — best-effort sync invalidate.
+        try:
+            session.sync_session.invalidate()
+        except BaseException:
+            _log.debug("detach-close: no-loop invalidate failed", exc_info=True)
+        return
+    task = loop.create_task(_cleanup())
+    _cleanup_tasks.add(task)
+    # Consume any exception to silence "Task exception was never retrieved".
+    task.add_done_callback(lambda t: (_cleanup_tasks.discard(t), t.exception()))
+
+
+@asynccontextmanager
+async def _safe_session(factory: async_sessionmaker[AsyncSession]):
+    """Session context manager that keeps close() reliable under cancellation.
+
+    Success path: await close() inline so the caller observes cleanup
+    (commit visibility, connection release) before proceeding.
+
+    Exception path (includes CancelledError from client disconnects):
+    detach close() to a fresh task.  The caller is unwinding and its
+    own cancellation would abort an inline close mid-rollback, leaving
+    the aiomysql connection orphaned.
+    """
+    session = factory()
+    try:
+        yield session
+    except BaseException:
+        _detach_close(session)
+        raise
+    else:
+        await session.close()