implement basic logging and update doc

README.md

@@ -51,6 +51,7 @@ $ jinja_to_js --help
 usage: jinja_to_js [-h] [-o [OUTFILE]] [-m [JS_MODULE_FORMAT]]
                    [-r [RUNTIME_PATH]] [-p [INCLUDE_PREFIX]]
                    [-i [INCLUDE_EXT]]
+				   [-f [CUSTOM_FILTERS [CUSTOM_FILTERS ...]]] [-v]
                    template_root template_name
 
 Convert Jinja templates into JavaScript functions.
@@ -81,6 +82,9 @@ optional arguments:
                         Specifies the prefix to use for included templates.
   -i [INCLUDE_EXT], --include-ext [INCLUDE_EXT]
                         Specifies the extension to use for included templates.
+  -f [CUSTOM_FILTERS [CUSTOM_FILTERS ...]], --filters [CUSTOM_FILTERS [CUSTOM_FILTERS ...]]
+                        Specifies custom filters to be allowed.
+  -v, --verbose         Log to standard out. Use two for debug.
 ```
 
 ## Supported Features

jinja_to_js/__init__.py

@@ -2,6 +2,7 @@
 from __future__ import unicode_literals
 
 import contextlib
+import logging
 import json
 import re
 import os
@@ -244,6 +245,7 @@ def __init__(self,
                 'The js_module_format option must be one of: %s' % JS_MODULE_FORMATS.keys()
             )
 
+        logging.info('Parsing template: {}'.format(self.template_name))
         self.ast = self.environment.parse(template_string)
 
         try:
@@ -317,6 +319,7 @@ def _process_extends(self, node, **kwargs):
         """
         Processes an extends block e.g. `{% extends "some/template.jinja" %}`
         """
+        logging.debug('Extends parent template: {}'.format(node.template.value))
 
         # find all the blocks in this template
         for b in self.ast.find_all(nodes.Block):
@@ -354,6 +357,7 @@ def _process_block(self, node, **kwargs):
         """
         Processes a block e.g. `{% block my_block %}{% endblock %}`
         """
+        logging.debug('Processing block: %s', node.name)
 
         # check if this node already has a 'super_block' attribute
         if not hasattr(node, 'super_block'):
@@ -635,6 +639,7 @@ def _process_call(self, node, super_block=None, **kwargs):
             # special case for the super() method which is available inside blocks
             if not super_block:
                 raise Exception('super() called outside of a block with a parent.')
+            logging.debug('explicit call to super(): %s', super_block.name)
             self._process_node(super_block, **kwargs)
 
         else:

jinja_to_js/__main__.py

@@ -3,6 +3,7 @@
 import sys
 
 import argparse
+import logging
 
 from . import JinjaToJS
 
@@ -75,20 +76,36 @@ def get_arg_parser():
         dest="custom_filters"
     )
 
+    parser.add_argument(
+        '-v', '--verbose', action='count',
+        help="Log to standard out. Use -vv for debug level.",
+        default=0,
+        dest="verbose"
+    )
+
     return parser
 
 
+def setup_logging(options):
+    if options.verbose:
+        level = logging.INFO
+        if options.verbose > 1:
+            level = logging.DEBUG
+        logging.basicConfig(format='%(levelname)-8s:%(message)s', level=level)
+
+
 def get_init_kwargs(options):
     kwargs = {}
     for key, value in vars(options).items():
-        if key != 'outfile':
+        if key not in ('outfile', 'verbose'):
             kwargs[key] = value
     return kwargs
 
 
 def main():
     parser = get_arg_parser()
     options = parser.parse_args()
+    setup_logging(options)
     compiler = JinjaToJS(**get_init_kwargs(options))
     options.outfile.write(compiler.get_output())
     return 0