From cee13ec0e28a95c3682cfeff105577d3fcee7e8a Mon Sep 17 00:00:00 2001
From: ZyX <kp-pav@yandex.ru>
Date: Sat, 30 Aug 2014 15:10:46 +0400
Subject: [PATCH] Add function that prints cyclic references to
 powerline.lib.debug

---
 powerline/lib/debug.py | 97 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100755 powerline/lib/debug.py

diff --git a/powerline/lib/debug.py b/powerline/lib/debug.py
new file mode 100755
index 00000000..d8f1d333
--- /dev/null
+++ b/powerline/lib/debug.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8:noet
+
+import gc
+import sys
+
+from types import FrameType
+from itertools import chain
+
+
+# From http://code.activestate.com/recipes/523004-find-cyclical-references/
+def print_cycles(objects, outstream=sys.stdout, show_progress=False):
+	'''Find reference cycles
+
+	:param list objects:
+		A list of objects to find cycles in.  It is often useful to pass in 
+		gc.garbage to find the cycles that are preventing some objects from 
+		being garbage collected.
+	:param file outstream:
+		The stream for output.
+	:param bool show_progress:
+		If True, print the number of objects reached as they are found.
+	'''
+	def print_path(path):
+		for i, step in enumerate(path):
+			# next "wraps around"
+			next = path[(i + 1) % len(path)]
+
+			outstream.write("	%s -- " % str(type(step)))
+			written = False
+			if isinstance(step, dict):
+				for key, val in step.items():
+					if val is next:
+						outstream.write("[%s]" % repr(key))
+						written = True
+						break
+					if key is next:
+						outstream.write("[key] = %s" % repr(val))
+						written = True
+						break
+			elif isinstance(step, (list, tuple)):
+				for i, item in enumerate(step):
+					if item is next:
+						outstream.write("[%d]" % i)
+						written = True
+			elif getattr(type(step), '__getattribute__', None) in (object.__getattribute__, type.__getattribute__):
+				for attr in chain(dir(step), getattr(step, '__dict__', ())):
+					if getattr(step, attr, None) is next:
+						try:
+							outstream.write('%r.%s' % (step, attr))
+						except TypeError:
+							outstream.write('.%s' % (step, attr))
+						written = True
+						break
+			if not written:
+				outstream.write(repr(step))
+			outstream.write(" ->\n")
+		outstream.write("\n")
+
+	def recurse(obj, start, all, current_path):
+		if show_progress:
+			outstream.write("%d\r" % len(all))
+
+		all[id(obj)] = None
+
+		referents = gc.get_referents(obj)
+		for referent in referents:
+			# If we've found our way back to the start, this is
+			# a cycle, so print it out
+			if referent is start:
+				try:
+					outstream.write('Cyclic reference: %r\n' % referent)
+				except TypeError:
+					try:
+						outstream.write('Cyclic reference: %i (%r)\n' % (id(referent), type(referent)))
+					except TypeError:
+						outstream.write('Cyclic reference: %i\n' % id(referent))
+				print_path(current_path)
+
+			# Don't go back through the original list of objects, or
+			# through temporary references to the object, since those
+			# are just an artifact of the cycle detector itself.
+			elif referent is objects or isinstance(referent, FrameType): 
+				continue
+
+			# We haven't seen this object before, so recurse
+			elif id(referent) not in all:
+				recurse(referent, start, all, current_path + (obj,))
+
+	for obj in objects:
+		# We are not interested in non-powerline cyclic references
+		try:
+			if not type(obj).__module__.startswith('powerline'):
+				continue
+		except AttributeError:
+			continue
+		recurse(obj, obj, {}, ())