Google Code Issue 157: Add "escape invisible characters" option

html5lib/constants.py

@@ -4,6 +4,9 @@
 import gettext
 _ = gettext.gettext
 
+from itertools import chain
+
+
 EOF = None
 
 E = {
@@ -3078,6 +3081,19 @@
 prefixes["http://www.w3.org/1998/Math/MathML"] = "math"
 
 
+invisibleChars = frozenset(chain(
+    # ASCII control chars
+    range(0x0, 0x9), range(0xB, 0xD), range(0xE, 0x20),
+    # Other control chars
+    # fixed-width spaces, zero-width marks, bidi marks
+    range(0x2000, 0x2010),
+    # LS, PS, bidi control codes
+    range(0x2028, 0x2030),
+    # nbsp, mathsp, ideosp, WJ, interlinear
+    [0x00A0, 0x205F, 0x3000, 0x2060, 0xFFF9, 0xFFFA, 0xFFFB]
+))
+
+
 class DataLossWarning(UserWarning):
     pass
 

html5lib/serializer/htmlserializer.py

@@ -94,6 +94,7 @@ class HTMLSerializer(object):
     # escaping options
     escape_lt_in_attrs = False
     escape_rcdata = False
+    escape_invisible = False
     resolve_entities = True
 
     # miscellaneous options
@@ -105,7 +106,8 @@ class HTMLSerializer(object):
                "minimize_boolean_attributes", "use_trailing_solidus",
                "space_before_trailing_solidus", "omit_optional_tags",
                "strip_whitespace", "inject_meta_charset", "escape_lt_in_attrs",
-               "escape_rcdata", "resolve_entities", "sanitize")
+               "escape_rcdata", "escape_invisible", "resolve_entities",
+               "sanitize")
 
     def __init__(self, **kwargs):
         """Initialize HTMLSerializer.
@@ -127,6 +129,10 @@ def __init__(self, **kwargs):
         escape_rcdata=False|True
           Whether to escape characters that need to be escaped within normal
           elements within rcdata elements such as style.
+        escape_invisible=False|True|'numeric'|'named'
+          Whether to escape invisible characters (such as nbsp, fixed-width
+          spaces, and control codes). Uses named HTML escapes if 'named'
+          is specified, otherwise uses numeric codes.
         resolve_entities=True|False
           Whether to resolve named character entities that appear in the
           source tree. The XML predefined entities < > & " '
@@ -160,6 +166,8 @@ def __init__(self, **kwargs):
 
     def encode(self, string):
         assert(isinstance(string, text_type))
+        if self.escape_invisible:
+            string = utils.escapeInvisible(string, self.escape_invisible == 'named')
         if self.encoding:
             return string.encode(self.encoding, unicode_encode_errors)
         else:

html5lib/utils.py

@@ -2,6 +2,10 @@
 
 from types import ModuleType
 
+from six import text_type
+
+from .constants import invisibleChars
+
 
 class MethodDispatcher(dict):
     """Dict with 2 special properties:
@@ -71,3 +75,27 @@ def moduleFactory(baseModule, *args, **kwargs):
             return mod
 
     return moduleFactory
+
+
+def escapeInvisible(text, useNamedEntities=False):
+    """Escape invisible characters other than Tab, LF, CR, and ASCII space
+    """
+    assert type(text) == text_type
+    # This algorithm is O(MN) for M len(text) and N num escapable
+    # But it doesn't modify the text when N is zero (common case) and
+    # N is expected to be small (usually 1 or 2) in most other cases.
+    escapable = set()
+    for c in text:
+        if ord(c) in invisibleChars:
+            escapable.add(c)
+    if useNamedEntities:
+        # for c in escapable:
+        #     name = codepoint2name.get(ord(c))
+        #     escape = "&%s;" % name if name else "&#x%X;" % ord(c)
+        #     text = text.replace(c, escape)
+        raise NotImplementedError("This doesn't work on Python 3")
+    else:
+        for c in escapable:
+            text = text.replace(c, "&#x%X;" % ord(c))
+
+    return text