Increase stack limit and mention truncation in debug stack dump

Lib/asyncio/coroutines.py

@@ -184,7 +184,7 @@ def __del__(self):
  if tb:
  tb = ''.join(traceback.format_list(tb))
  msg += ('\nCoroutine object created at '
- '(most recent call last):\n')
+ '(most recent call last, maybe truncated):\n')
  msg += tb.rstrip()
  logger.error(msg)
 

Lib/asyncio/events.py

@@ -79,10 +79,9 @@ def extract_stack(f=None, limit=None):
  if f is None:
  f = sys._getframe().f_back
  if limit is None:
- # This is heuristically the max number of entries we're gonna pop + 1
- # (we're only interested in displaying the top of stack)
- # If this is too small, tests will fail.
- limit = 4
+ # This is enough for decent debug information and puts
+ # a reasonable on the amount of work we have to do here.
+ limit = 10
  stack = traceback.StackSummary.extract(traceback.walk_stack(f),
  limit=limit,
  lookup_lines=False)

Lib/test/test_asyncio/test_tasks.py

@@ -1981,7 +1981,7 @@ def coro_noop():
 
  regex = (r'^<CoroWrapper %s\(?\)? .* at %s:%s, .*> '
  r'was never yielded from\n'
- r'Coroutine object created at \(most recent call last\):\n'
+ r'Coroutine object created at \(most recent call last, maybe truncated\):\n'
  r'.*\n'
  r' File "%s", line %s, in test_coroutine_never_yielded\n'
  r' coro_noop\(\)$'