[Python-checkins] asyncio: __del__() keep reference to warnings.warn (GH-11491)

[Victor Stinner]

https://github.com/python/cpython/commit/fb2c3465f09e1f720cdae7eca87d62125a327fd9
commit: fb2c3465f09e1f720cdae7eca87d62125a327fd9
branch: master
author: Victor Stinner <vstinner at redhat.com>
committer: GitHub <noreply at github.com>
date: 2019-01-10T11:24:40+01:00
summary:

asyncio: __del__() keep reference to warnings.warn (GH-11491)

* asyncio: __del__() keep reference to warnings.warn

The __del__() methods of asyncio classes now keep a strong reference
to the warnings.warn() to be able to display the ResourceWarning
warning in more cases. Ensure that the function remains available if
instances are destroyed late during Python shutdown (while module
symbols are cleared).

* Rename warn parameter to _warn

"_warn" name is a hint that it's not the regular warnings.warn()
function.

files:
M Lib/asyncio/base_events.py
M Lib/asyncio/base_subprocess.py
M Lib/asyncio/proactor_events.py
M Lib/asyncio/selector_events.py
M Lib/asyncio/sslproto.py
M Lib/asyncio/unix_events.py
M Lib/asyncio/windows_utils.py

diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index 60a189bdfb7e..cec47ce67f38 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -622,10 +622,9 @@ def is_closed(self):
         """Returns True if the event loop was closed."""
         return self._closed
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if not self.is_closed():
-            warnings.warn(f"unclosed event loop {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed event loop {self!r}", ResourceWarning, source=self)
             if not self.is_running():
                 self.close()
 
diff --git a/Lib/asyncio/base_subprocess.py b/Lib/asyncio/base_subprocess.py
index b547c444ad5d..f503f78fdda3 100644
--- a/Lib/asyncio/base_subprocess.py
+++ b/Lib/asyncio/base_subprocess.py
@@ -120,10 +120,9 @@ def close(self):
 
             # Don't clear the _proc reference yet: _post_init() may still run
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if not self._closed:
-            warnings.warn(f"unclosed transport {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
             self.close()
 
     def get_pid(self):
diff --git a/Lib/asyncio/proactor_events.py b/Lib/asyncio/proactor_events.py
index da204c69d45e..3a1826e2c0d2 100644
--- a/Lib/asyncio/proactor_events.py
+++ b/Lib/asyncio/proactor_events.py
@@ -89,10 +89,9 @@ def close(self):
             self._read_fut.cancel()
             self._read_fut = None
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if self._sock is not None:
-            warnings.warn(f"unclosed transport {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
             self.close()
 
     def _fatal_error(self, exc, message='Fatal error on pipe transport'):
diff --git a/Lib/asyncio/selector_events.py b/Lib/asyncio/selector_events.py
index 112c4b15b8d8..93b688950943 100644
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -658,10 +658,9 @@ def close(self):
             self._loop._remove_writer(self._sock_fd)
             self._loop.call_soon(self._call_connection_lost, None)
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if self._sock is not None:
-            warnings.warn(f"unclosed transport {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
             self._sock.close()
 
     def _fatal_error(self, exc, message='Fatal error on transport'):
diff --git a/Lib/asyncio/sslproto.py b/Lib/asyncio/sslproto.py
index 12fdb0d1c5ec..42785609dcd2 100644
--- a/Lib/asyncio/sslproto.py
+++ b/Lib/asyncio/sslproto.py
@@ -316,10 +316,9 @@ def close(self):
         self._closed = True
         self._ssl_protocol._start_shutdown()
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if not self._closed:
-            warnings.warn(f"unclosed transport {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
             self.close()
 
     def is_reading(self):
diff --git a/Lib/asyncio/unix_events.py b/Lib/asyncio/unix_events.py
index 1a62db4f59bc..73d4bda7c234 100644
--- a/Lib/asyncio/unix_events.py
+++ b/Lib/asyncio/unix_events.py
@@ -511,10 +511,9 @@ def close(self):
         if not self._closing:
             self._close(None)
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if self._pipe is not None:
-            warnings.warn(f"unclosed transport {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
             self._pipe.close()
 
     def _fatal_error(self, exc, message='Fatal error on pipe transport'):
@@ -707,10 +706,9 @@ def close(self):
             # write_eof is all what we needed to close the write pipe
             self.write_eof()
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if self._pipe is not None:
-            warnings.warn(f"unclosed transport {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
             self._pipe.close()
 
     def abort(self):
diff --git a/Lib/asyncio/windows_utils.py b/Lib/asyncio/windows_utils.py
index 9e22f6e0740e..ef277fac3e29 100644
--- a/Lib/asyncio/windows_utils.py
+++ b/Lib/asyncio/windows_utils.py
@@ -107,10 +107,9 @@ def close(self, *, CloseHandle=_winapi.CloseHandle):
             CloseHandle(self._handle)
             self._handle = None
 
-    def __del__(self):
+    def __del__(self, _warn=warnings.warn):
         if self._handle is not None:
-            warnings.warn(f"unclosed {self!r}", ResourceWarning,
-                          source=self)
+            _warn(f"unclosed {self!r}", ResourceWarning, source=self)
             self.close()
 
     def __enter__(self):