asyncio: Tulip issue 173: Enhance repr(Handle) and repr(Task)

repr(Handle) is shorter for function: "foo" instead of "<function foo at
0x...>". It now also includes the source of the callback, filename and line
number where it was defined, if available.

repr(Task) now also includes the current position in the code, filename and
line number, if available. If the coroutine (generator) is done, the line
number is omitted and "done" is added.

Lib/asyncio/events.py

@@ -8,9 +8,29 @@ __all__ = ['AbstractEventLoopPolicy',
            'get_child_watcher', 'set_child_watcher',
            ]
 
+import functools
+import inspect
 import subprocess
 import threading
 import socket
+import sys
+
+
+_PY34 = sys.version_info >= (3, 4)
+
+def _get_function_source(func):
+    if _PY34:
+        func = inspect.unwrap(func)
+    elif hasattr(func, '__wrapped__'):
+        func = func.__wrapped__
+    if inspect.isfunction(func):
+        code = func.__code__
+        return (code.co_filename, code.co_firstlineno)
+    if isinstance(func, functools.partial):
+        return _get_function_source(func.func)
+    if _PY34 and isinstance(func, functools.partialmethod):
+        return _get_function_source(func.func)
+    return None
 
 
 class Handle:
@@ -26,7 +46,15 @@ class Handle:
         self._cancelled = False
 
     def __repr__(self):
-        res = 'Handle({}, {})'.format(self._callback, self._args)
+        cb_repr = getattr(self._callback, '__qualname__', None)
+        if not cb_repr:
+            cb_repr = str(self._callback)
+
+        source = _get_function_source(self._callback)
+        if source:
+            cb_repr += ' at %s:%s' % source
+
+        res = 'Handle({}, {})'.format(cb_repr, self._args)
         if self._cancelled:
             res += '<cancelled>'
         return res