Fixed #84

gino/__init__.py

@@ -1,7 +1,13 @@
 from .api import Gino
 from .pool import GinoPool
 from .connection import GinoConnection
-from .local import get_local, enable_task_local, disable_task_local
+from .local import (
+    get_local,
+    enable_task_local,
+    disable_task_local,
+    reset_local,
+    is_local_root,
+)
 from .exceptions import *
 
 __version__ = '0.5.4'

gino/local.py

@@ -6,21 +6,67 @@
 
 
 def get_local():
+    """Get local storage from current task.
+
+    Returns a dict if task local is enabled for current loop, or ``None``
+    otherwise. Please note, if you create a new task from an existing task,
+    the new task will by default inherit the same local storage object from
+    the existing task. Use ``is_local_root` to check the inherit state, and use
+    ``reset_local`` to spawn tasks without inheriting. See the two functions
+    for more information.
+    """
     return getattr(asyncio.Task.current_task(), 'task_local', None)
 
 
 def task_factory(loop, coro):
-    orig = _original_task_factories.get(loop)
-    loop.set_task_factory(orig)
-    task = loop.create_task(coro)
-    loop.set_task_factory(task_factory)
+    loop.set_task_factory(_original_task_factories.get(loop))
+    try:
+        task = loop.create_task(coro)
+        if getattr(task, '_source_traceback', None):
+            del getattr(task, '_source_traceback')[-2:]
+
+        local = get_local()
+        task.task_local = {} if local is None else local
+        task.task_local_is_root = local is None
+
+        return task
+    finally:
+        loop.set_task_factory(task_factory)
+
+
+def reset_local(coro_or_future=None, *, loop=None):
+    """Reset local to empty dict within given routine, or current if not given.
+
+    Please note, this works only if the local was inherited from another
+    routine, or this is a no-op. That means, calling ``reset_local`` a second
+    time on the same routine won't set its local to empty dict, because its
+    local was already non-inherited after the first call.
+
+    This method always return a future object. New task will be created and
+    returned if the parameter is a coroutine or awaitable object. Therefore it
+    is practical to use this method to spawn detached tasks.
+    """
+    if coro_or_future is None:
+        coro_or_future = asyncio.Task.current_task()
+
+    if asyncio.isfuture(coro_or_future):
+        if is_local_root(coro_or_future) is False:
+            coro_or_future.task_local = {}
+            coro_or_future.task_local_is_root = True
+        return coro_or_future
+    else:
+        return reset_local(asyncio.ensure_future(coro_or_future, loop=loop))
 
-    if getattr(task, '_source_traceback', None):
-        del getattr(task, '_source_traceback')[-2:]
 
-    task.task_local = get_local() or {}
+def is_local_root(task=None):
+    """Check if local of the given task is inherited or not.
 
-    return task
+    If task is not given, current task is used. Returns ``None`` if the task
+    has no local, or ``True``/``False`` for the inherit state.
+    """
+    if task is None:
+        task = asyncio.Task.current_task()
+    return getattr(task, 'task_local_is_root', None)
 
 
 def enable_task_local(loop=None):

gino/pool.py

@@ -46,6 +46,10 @@ def metadata(self):
     def execution_options(self):
         return self._execution_options
 
+    @property
+    def is_root(self):
+        return self._root is self
+
     async def get_connection(self):
         if self._closed:
             raise InterfaceError('This LazyConnection is returned to pool')

tests/test_local.py

@@ -0,0 +1,85 @@
+import asyncio
+
+import pytest
+from gino import get_local, reset_local, is_local_root
+
+pytestmark = pytest.mark.asyncio
+
+
+async def sub(result):
+    result.append(get_local().get('val'))
+
+
+# noinspection PyUnusedLocal
+async def test_attached(task_local):
+    get_local()['val'] = 123
+    result = []
+    await asyncio.ensure_future(sub(result))
+    assert result[0] == 123
+
+
+# noinspection PyUnusedLocal
+async def test_detached(task_local):
+    get_local()['val'] = 123
+    result = []
+    await reset_local(sub(result))
+    assert result[0] is None
+
+
+async def test_reset_disabled():
+    result = []
+    fut = reset_local(sub(result))
+    with pytest.raises(AttributeError):
+        await fut
+    assert len(result) == 0
+
+
+async def sub_set():
+    get_local()['val'] = 123
+
+
+# noinspection PyUnusedLocal
+async def test_attached_reverse(task_local):
+    await asyncio.ensure_future(sub_set())
+    assert get_local().get('val') == 123
+
+
+# noinspection PyUnusedLocal
+async def test_detached_reverse(task_local):
+    await reset_local(sub_set())
+    assert get_local().get('val') is None
+
+
+# noinspection PyUnusedLocal
+async def test_accept_task(task_local):
+    await reset_local(asyncio.ensure_future(sub_set()))
+    assert get_local().get('val') is None
+
+
+async def grand_sub():
+    assert not is_local_root()
+    assert get_local().get('val') == 456
+
+
+async def sub_reset():
+    assert is_local_root() is False
+    assert get_local().get('val') == 123
+
+    reset_local()
+    assert is_local_root()
+    assert get_local().get('val') is None
+
+    get_local()['val'] = 456
+    assert get_local().get('val') == 456
+    await asyncio.ensure_future(grand_sub())
+
+    reset_local()
+    assert get_local().get('val') == 456
+    await asyncio.ensure_future(grand_sub())
+
+
+# noinspection PyUnusedLocal
+async def test_inline_reset(task_local):
+    get_local()['val'] = 123
+    await asyncio.ensure_future(sub_reset())
+    get_local()['val'] = 123