Merge pull request #706 from ZyX-I/better-errors

Better error handling

powerline/__init__.py

@@ -10,10 +10,43 @@ from powerline.lib.config import ConfigLoader
 
 from threading import Lock, Event
 
+try:
+	from __builtin__ import unicode
+except ImportError:
+	unicode = str  # NOQA
+
 
 DEFAULT_SYSTEM_CONFIG_DIR = None
 
 
+def safe_unicode(s):
+	'''Return unicode instance without raising an exception.
+	'''
+	try:
+		try:
+			return unicode(s)
+		except UnicodeDecodeError:
+			try:
+				return unicode(s, 'utf-8')
+			except TypeError:
+				return unicode(str(s), 'utf-8')
+	except Exception as e:
+		return safe_unicode(e)
+
+
+class FailedUnicode(unicode):
+	'''Builtin ``unicode`` (``str`` in python 3) subclass indicating fatal 
+	error.
+
+	If your code for some reason wants to determine whether `.render()` method 
+	failed it should check returned string for being a FailedUnicode instance. 
+	Alternatively you could subclass Powerline and override `.render()` method 
+	to do what you like in place of catching the exception and returning 
+	FailedUnicode.
+	'''
+	pass
+
+
 def find_config_file(search_paths, config_file):
 	config_file += '.json'
 	for path in search_paths:
@@ -61,6 +94,29 @@ class PowerlineLogger(object):
 		self._log('debug', msg, *args, **kwargs)
 
 
+_fallback_logger = None
+
+
+def _get_fallback_logger():
+	global _fallback_logger
+	if _fallback_logger:
+		return _fallback_logger
+
+	log_format = '%(asctime)s:%(levelname)s:%(message)s'
+	formatter = logging.Formatter(log_format)
+
+	level = logging.WARNING
+	handler = logging.StreamHandler()
+	handler.setLevel(level)
+	handler.setFormatter(formatter)
+
+	logger = logging.getLogger('powerline')
+	logger.setLevel(level)
+	logger.addHandler(handler)
+	_fallback_logger = PowerlineLogger(None, logger, '_fallback_')
+	return _fallback_logger
+
+
 class Powerline(object):
 	'''Main powerline class, entrance point for all powerline uses. Sets 
 	powerline up and loads the configuration.
@@ -233,7 +289,7 @@ class Powerline(object):
 			try:
 				Renderer = __import__(self.renderer_module, fromlist=['renderer']).renderer
 			except Exception as e:
-				self.pl.exception('Failed to import renderer module: {0}', str(e))
+				self.exception('Failed to import renderer module: {0}', str(e))
 				sys.exit(1)
 
 			# Renderer updates configuration file via segments’ .startup thus it 
@@ -242,7 +298,7 @@ class Powerline(object):
 			try:
 				renderer = Renderer(**self.renderer_options)
 			except Exception as e:
-				self.pl.exception('Failed to construct renderer object: {0}', str(e))
+				self.exception('Failed to construct renderer object: {0}', str(e))
 				if not hasattr(self, 'renderer'):
 					raise
 			else:
@@ -360,16 +416,34 @@ class Powerline(object):
 			try:
 				self.create_renderer(**create_renderer_kwargs)
 			except Exception as e:
-				self.pl.exception('Failed to create renderer: {0}', str(e))
+				self.exception('Failed to create renderer: {0}', str(e))
-			finally:
+				if hasattr(self, 'renderer'):
-				self.create_renderer_kwargs.clear()
+					with self.cr_kwargs_lock:
+						self.create_renderer_kwargs.clear()
+				else:
+					raise
+			else:
+				with self.cr_kwargs_lock:
+					self.create_renderer_kwargs.clear()
 
 	def render(self, *args, **kwargs):
 		'''Update/create renderer if needed and pass all arguments further to 
 		``self.renderer.render()``.
 		'''
-		self.update_renderer()
+		try:
-		return self.renderer.render(*args, **kwargs)
+			self.update_renderer()
+			return self.renderer.render(*args, **kwargs)
+		except Exception as e:
+			try:
+				self.exception('Failed to render: {0}', str(e))
+			except Exception as e:
+				# Updates e variable to new value, masking previous one. 
+				# Normally it is the same exception (due to raise in case pl is 
+				# unset), but it may also show error in logger. Note that latter 
+				# is not logged by logger for obvious reasons, thus this also 
+				# prevents us from seeing logger traceback.
+				pass
+			return FailedUnicode(safe_unicode(e))
 
 	def shutdown(self):
 		'''Shut down all background threads. Must be run only prior to exiting 
@@ -410,3 +484,9 @@ class Powerline(object):
 
 	def __exit__(self, *args):
 		self.shutdown()
+
+	def exception(self, msg, *args, **kwargs):
+		if 'prefix' not in kwargs:
+			kwargs['prefix'] = 'powerline'
+		pl = getattr(self, 'pl', None) or _get_fallback_logger()
+		return pl.exception(msg, *args, **kwargs)

powerline/lib/config.py

@@ -155,6 +155,10 @@ class ConfigLoader(MultiRunnedThread):
 			try:
 				self.loaded[path] = deepcopy(self._load(path))
 			except Exception as e:
+				try:
+					self.loaded.pop(path)
+				except KeyError:
+					pass
 				self.exception('Error while loading {0}: {1}', path, str(e))
 
 	def run(self):

powerline/segments/common.py

@@ -707,13 +707,13 @@ class NetworkLoadSegment(KwThreadedSegment):
 						total = activity
 						interface = name
 
-		if interface in self.interfaces:
+		try:
 			idata = self.interfaces[interface]
 			try:
 				idata['prev'] = idata['last']
 			except KeyError:
 				pass
-		else:
+		except KeyError:
 			idata = {}
 			if self.run_once:
 				idata['prev'] = (monotonic(), _get_bytes(interface))

tests/test_config_reload.py

@@ -141,7 +141,7 @@ class TestConfigReload(TestCase):
 				self.assertEqual(p.render(), '<1 2 1> s <2 4 False>>><3 4 4>g <4 False False>>><None None None>')
 				self.assertAccessEvents('config', 'themes/test/nonexistent')
 				# It should normally handle file missing error
-				self.assertEqual(p.logger._pop_msgs(), ['exception:test:Failed to create renderer: themes/test/nonexistent'])
+				self.assertEqual(p.logger._pop_msgs(), ['exception:test:powerline:Failed to create renderer: themes/test/nonexistent'])
 
 				config['config']['ext']['test']['theme'] = 'default'
 				add_watcher_events(p, 'config')
@@ -154,7 +154,7 @@ class TestConfigReload(TestCase):
 				self.assertEqual(p.render(), '<1 2 1> s <2 4 False>>><3 4 4>g <4 False False>>><None None None>')
 				self.assertAccessEvents('config', 'colorschemes/test/nonexistent')
 				# It should normally handle file missing error
-				self.assertEqual(p.logger._pop_msgs(), ['exception:test:Failed to create renderer: colorschemes/test/nonexistent'])
+				self.assertEqual(p.logger._pop_msgs(), ['exception:test:powerline:Failed to create renderer: colorschemes/test/nonexistent'])
 
 				config['config']['ext']['test']['colorscheme'] = '2'
 				add_watcher_events(p, 'config')
@@ -187,7 +187,7 @@ class TestConfigReload(TestCase):
 				add_watcher_events(p, 'config')
 				self.assertEqual(p.render(), '<1 2 1> s<2 4 False>>><3 4 4>g<4 False False>>><None None None>')
 				self.assertAccessEvents('config')
-				self.assertIn('exception:test:Failed to create renderer: fcf:colorschemes/test/nonexistentraise', p.logger._pop_msgs())
+				self.assertIn('exception:test:powerline:Failed to create renderer: fcf:colorschemes/test/nonexistentraise', p.logger._pop_msgs())
 
 				config['colorschemes/test/nonexistentraise'] = {
 					'groups': {