rewrite: when using lxml parser, just pass raw stream to lxml

without decoding. lxml parser expects to have raw bytes and will determine
encoding on its own. then serve back as utf-8 if no encoding specified.
should address #36

pywb/rewrite/lxml_html_rewriter.py

@@ -79,7 +79,8 @@ class RewriterTarget(object):
     def data(self, data):
         if not self.rewriter._wb_parse_context:
             data = cgi.escape(data, quote=True)
-
+            if isinstance(data, unicode):
+                data = data.replace(u'\xa0', ' ')
         self.rewriter.parse_data(data)
 
     def comment(self, data):

pywb/rewrite/rewrite_content.py

@@ -6,7 +6,7 @@ from io import BytesIO
 
 from header_rewriter import RewrittenStatusAndHeaders
 
-from rewriterules import RewriteRules
+from rewriterules import RewriteRules, is_lxml
 
 from pywb.utils.dsrules import RuleSet
 from pywb.utils.statusandheaders import StatusAndHeaders
@@ -73,21 +73,25 @@ class RewriteContent:
         # ====================================================================
         # special case -- need to ungzip the body
 
+        text_type = rewritten_headers.text_type
+        stream_raw = False
+        encoding = None
+        first_buff = None
+
         if (rewritten_headers.
              contains_removed_header('content-encoding', 'gzip')):
             stream = DecompressingBufferedReader(stream, decomp_type='gzip')
 
         if rewritten_headers.charset:
             encoding = rewritten_headers.charset
-            first_buff = None
+        elif is_lxml() and text_type == 'html':
+            stream_raw = True
         else:
             (encoding, first_buff) = self._detect_charset(stream)
 
-            # if chardet thinks its ascii, use utf-8
-            if encoding == 'ascii':
-                encoding = 'utf-8'
-
-        text_type = rewritten_headers.text_type
+        # if encoding not set or chardet thinks its ascii, use utf-8
+        if not encoding or encoding == 'ascii':
+            encoding = 'utf-8'
 
         rule = self.ruleset.get_first_match(urlkey)
 
@@ -108,34 +112,33 @@ class RewriteContent:
                                       js_rewriter_class=rule.rewriters['js'],
                                       css_rewriter_class=rule.rewriters['css'],
                                       head_insert=head_insert_str)
+
         else:
         # apply one of (js, css, xml) rewriters
             rewriter = rewriter_class(urlrewriter)
 
         # Create rewriting generator
-        gen = self._rewriting_stream_gen(rewriter, encoding,
+        gen = self._rewriting_stream_gen(rewriter, encoding, stream_raw,
                                          stream, first_buff)
 
         return (status_headers, gen, True)
 
     # Create rewrite stream,  may even be chunked by front-end
-    def _rewriting_stream_gen(self, rewriter, encoding,
+    def _rewriting_stream_gen(self, rewriter, encoding, stream_raw,
                               stream, first_buff=None):
         def do_rewrite(buff):
-            if encoding:
+            if not stream_raw:
                 buff = self._decode_buff(buff, stream, encoding)
 
             buff = rewriter.rewrite(buff)
 
-            if encoding:
-                buff = buff.encode(encoding)
+            buff = buff.encode(encoding)
 
             return buff
 
         def do_finish():
             result = rewriter.close()
-            if encoding:
-                result = result.encode(encoding)
+            result = result.encode(encoding)
 
             return result
 
@@ -188,12 +191,16 @@ class RewriteContent:
     def stream_to_gen(stream, rewrite_func=None,
                       final_read_func=None, first_buff=None):
         try:
-            buff = first_buff if first_buff else stream.read()
+            if first_buff:
+                buff = first_buff
+            else:
+                buff = stream.read() + stream.readline()
+
             while buff:
                 if rewrite_func:
                     buff = rewrite_func(buff)
                 yield buff
-                buff = stream.read()
+                buff = stream.read() + stream.readline()
 
             # For adding a tail/handling final buffer
             if final_read_func:

pywb/rewrite/rewriterules.py

@@ -9,6 +9,7 @@ from html_rewriter import HTMLRewriter
 import itertools
 
 HTML = HTMLRewriter
+_is_lxml = False
 
 
 #=================================================================
@@ -18,13 +19,19 @@ def use_lxml_parser():
 
     if LXML_SUPPORTED:
         global HTML
+        global _is_lxml
         HTML = LXMLHTMLRewriter
         logging.debug('Using LXML Parser')
-        return True
+        _is_lxml = True
     else:  # pragma: no cover
         logging.debug('LXML Parser not available')
-        return False
+        _is_lxml = False
 
+    return _is_lxml
+
+
+def is_lxml():
+    return _is_lxml
 
 #=================================================================
 class RewriteRules(BaseRule):

pywb/rewrite/test/test_lxml_html_rewriter.py

@@ -119,6 +119,15 @@ ur"""
 >>> p = LXMLHTMLRewriter(urlrewriter)
 >>> p.close()
 ''
+
+# test  
+>>> parse(' ')
+<html><body><p>&nbsp;</p></body></html>
+
+# test multiple rewrites: &nbsp; extra >, split comment
+>>> p = LXMLHTMLRewriter(urlrewriter)
+>>> p.rewrite('<div>&nbsp; &nbsp; > <!-- a') + p.rewrite('b --></div>') + p.close()
+u'<html><body><div>&nbsp; &nbsp; &gt; <!-- ab --></div></body></html>'
 """
 
 from pywb.rewrite.url_rewriter import UrlRewriter