Create a way to log to the list in Vim

docs/source/configuration/local.rst

@@ -31,6 +31,12 @@ Vim configuration can be overridden using the following options:
     If this variable is set to a true value it will prevent Powerline from reporting 
     an error when loaded in a copy of vim without the necessary Python support.
 
+``g:powerline_use_var_handler``
+    This variable may be set to either 0 or 1. If it is set to 1 then Vim will 
+    save log in ``g:powerline_log_messages`` variable in addition to whatever 
+    was configured in :ref:`log_* options <config-common-log>`. Level is always 
+    :ref:`log_level <config-common-log_level>`, same for format.
+
 Powerline script overrides
 ==========================
 

docs/source/configuration/reference.rst

@@ -98,6 +98,8 @@ Common configuration is a subdictionary that is a value of ``common`` key in
     Defines path which will hold powerline logs. If not present, logging will be 
     done to stderr.
 
+.. _config-common-log_level:
+
 ``log_level``
     String, determines logging level. Defaults to ``WARNING``.
 

powerline/__init__.py

@@ -424,6 +424,14 @@ class Powerline(object):
 	Usually returns encoding of the current locale.
 	'''
 
+	def create_logger(self):
+		'''Create logger
+
+		This function is used to create logger unless it was already specified 
+		at initialization.
+		'''
+		return create_logger(self.common_config, self.default_log_stream)
+
 	def create_renderer(self, load_main=False, load_colors=False, load_colorscheme=False, load_theme=False):
 		'''(Re)create renderer object. Can be used after Powerline object was 
 		successfully initialized. If any of the below parameters except 
@@ -461,7 +469,7 @@ class Powerline(object):
 				self.import_paths = self.common_config['paths']
 
 				if not self.logger:
-					self.logger = create_logger(self.common_config, self.default_log_stream)
+					self.logger = self.create_logger()
 
 				if not self.pl:
 					self.pl = PowerlineLogger(self.use_daemon_threads, self.logger, self.ext)

powerline/vim.py

@@ -3,14 +3,16 @@ from __future__ import (unicode_literals, division, absolute_import, print_funct
 
 import sys
 import json
+import logging
 
 from itertools import count
 
 import vim
 
-from powerline.bindings.vim import vim_get_func, vim_getvar, get_vim_encoding
+from powerline.bindings.vim import vim_get_func, vim_getvar, get_vim_encoding, python_to_vim
 from powerline import Powerline, FailedUnicode
 from powerline.lib.dict import mergedicts
+from powerline.lib.unicode import u
 
 
 def _override_from(config, override_varname):
@@ -22,6 +24,24 @@ def _override_from(config, override_varname):
 	return config
 
 
+class VimVarHandler(logging.Handler):
+	'''Vim-specific handler which emits messages to Vim global variables
+
+	Used variable: ``g:powerline_log_messages``.
+	'''
+	def __init__(self, *args, **kwargs):
+		super(VimVarHandler, self).__init__(*args, **kwargs)
+		vim.command('unlet! g:powerline_log_messages')
+		vim.command('let g:powerline_log_messages = []')
+
+	@staticmethod
+	def emit(record):
+		message = u(record.message)
+		if record.exc_text:
+			message += '\n' + u(record.exc_text)
+		vim.eval(b'add(g:powerline_log_messages, ' + python_to_vim(message) + b')')
+
+
 class VimPowerline(Powerline):
 	def init(self, pyeval='PowerlinePyeval', **kwargs):
 		super(VimPowerline, self).init('vim', **kwargs)
@@ -31,6 +51,18 @@ class VimPowerline(Powerline):
 
 	default_log_stream = sys.stdout
 
+	def create_logger(self):
+		logger = super(VimPowerline, self).create_logger()
+		try:
+			if int(vim_getvar('powerline_use_var_handler')):
+				formatter = logging.Formatter(self.common_config['log_format'])
+				handler = VimVarHandler(getattr(logging, self.common_config['log_level']))
+				handler.setFormatter(formatter)
+				logger.addHandler(handler)
+		except KeyError:
+			pass
+		return logger
+
 	def add_local_theme(self, key, config):
 		'''Add local themes at runtime (during vim session).