bpo-32253: Deprecate with statement and bare await for asyncio locks (GH-4764)

* Add test for 'with (yield from lock)'
* Deprecate with statement for asyncio locks
* Document the deprecation

Lib/test/test_asyncio/test_locks.py

@@ -42,7 +42,8 @@ class LockTests(test_utils.TestCase):
 
         @asyncio.coroutine
         def acquire_lock():
-            yield from lock
+            with self.assertWarns(DeprecationWarning):
+                yield from lock
 
         self.loop.run_until_complete(acquire_lock())
         self.assertTrue(repr(lock).endswith('[locked]>'))
@@ -53,7 +54,8 @@ class LockTests(test_utils.TestCase):
 
         @asyncio.coroutine
         def acquire_lock():
-            return (yield from lock)
+            with self.assertWarns(DeprecationWarning):
+                return (yield from lock)
 
         res = self.loop.run_until_complete(acquire_lock())
 
@@ -63,6 +65,32 @@ class LockTests(test_utils.TestCase):
         lock.release()
         self.assertFalse(lock.locked())
 
+    def test_lock_by_with_statement(self):
+        loop = asyncio.new_event_loop()  # don't use TestLoop quirks
+        self.set_event_loop(loop)
+        primitives = [
+            asyncio.Lock(loop=loop),
+            asyncio.Condition(loop=loop),
+            asyncio.Semaphore(loop=loop),
+            asyncio.BoundedSemaphore(loop=loop),
+        ]
+
+        @asyncio.coroutine
+        def test(lock):
+            yield from asyncio.sleep(0.01, loop=loop)
+            self.assertFalse(lock.locked())
+            with self.assertWarns(DeprecationWarning):
+                with (yield from lock) as _lock:
+                    self.assertIs(_lock, None)
+                    self.assertTrue(lock.locked())
+                    yield from asyncio.sleep(0.01, loop=loop)
+                    self.assertTrue(lock.locked())
+                self.assertFalse(lock.locked())
+
+        for primitive in primitives:
+            loop.run_until_complete(test(primitive))
+            self.assertFalse(primitive.locked())
+
     def test_acquire(self):
         lock = asyncio.Lock(loop=self.loop)
         result = []
@@ -212,7 +240,8 @@ class LockTests(test_utils.TestCase):
 
         @asyncio.coroutine
         def acquire_lock():
-            return (yield from lock)
+            with self.assertWarns(DeprecationWarning):
+                return (yield from lock)
 
         with self.loop.run_until_complete(acquire_lock()):
             self.assertTrue(lock.locked())
@@ -224,7 +253,8 @@ class LockTests(test_utils.TestCase):
 
         @asyncio.coroutine
         def acquire_lock():
-            return (yield from lock)
+            with self.assertWarns(DeprecationWarning):
+                return (yield from lock)
 
         # This spells "yield from lock" outside a generator.
         cm = self.loop.run_until_complete(acquire_lock())
@@ -668,7 +698,8 @@ class ConditionTests(test_utils.TestCase):
 
         @asyncio.coroutine
         def acquire_cond():
-            return (yield from cond)
+            with self.assertWarns(DeprecationWarning):
+                return (yield from cond)
 
         with self.loop.run_until_complete(acquire_cond()):
             self.assertTrue(cond.locked())
@@ -751,7 +782,8 @@ class SemaphoreTests(test_utils.TestCase):
 
         @asyncio.coroutine
         def acquire_lock():
-            return (yield from sem)
+            with self.assertWarns(DeprecationWarning):
+                return (yield from sem)
 
         res = self.loop.run_until_complete(acquire_lock())
 
@@ -893,7 +925,8 @@ class SemaphoreTests(test_utils.TestCase):
 
         @asyncio.coroutine
         def acquire_lock():
-            return (yield from sem)
+            with self.assertWarns(DeprecationWarning):
+                return (yield from sem)
 
         with self.loop.run_until_complete(acquire_lock()):
             self.assertFalse(sem.locked())