Fixed #5025 -- Add a "truncatechars" template filter. Many thanks to Chris Beaven.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16542 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/admin/widgets.py

@@ -9,7 +9,7 @@ from django.forms.widgets import RadioFieldRenderer
 from django.forms.util import flatatt
 from django.templatetags.static import static
 from django.utils.html import escape
-from django.utils.text import truncate_words
+from django.utils.text import Truncator
 from django.utils.translation import ugettext as _
 from django.utils.safestring import mark_safe
 from django.utils.encoding import force_unicode
@@ -152,7 +152,7 @@ class ForeignKeyRawIdWidget(forms.TextInput):
         key = self.rel.get_related_field().name
         try:
             obj = self.rel.to._default_manager.using(self.db).get(**{key: value})
-            return '&nbsp;<strong>%s</strong>' % escape(truncate_words(obj, 14))
+            return '&nbsp;<strong>%s</strong>' % escape(Truncator(obj).words(14, truncate='...'))
         except (ValueError, self.rel.to.DoesNotExist):
             return ''
 

django/template/defaultfilters.py

@@ -15,7 +15,7 @@ from django.utils.encoding import force_unicode, iri_to_uri
 from django.utils.html import (conditional_escape, escapejs, fix_ampersands,
     escape, urlize as urlize_impl, linebreaks, strip_tags)
 from django.utils.http import urlquote
-from django.utils.text import truncate_words, truncate_html_words, wrap, phone2numeric
+from django.utils.text import Truncator, wrap, phone2numeric
 from django.utils.safestring import mark_safe, SafeData, mark_for_escaping
 from django.utils.timesince import timesince, timeuntil
 from django.utils.translation import ugettext, ungettext
@@ -244,6 +244,20 @@ def title(value):
 title.is_safe = True
 title = stringfilter(title)
 
+def truncatechars(value, arg):
+    """
+    Truncates a string after a certain number of characters.
+
+    Argument: Number of characters to truncate after.
+    """
+    try:
+        length = int(arg)
+    except ValueError: # Invalid literal for int().
+        return value # Fail silently.
+    return Truncator(value).chars(value, length)
+truncatechars.is_safe = True
+truncatechars = stringfilter(truncatechars)
+
 def truncatewords(value, arg):
     """
     Truncates a string after a certain number of words.
@@ -256,7 +270,7 @@ def truncatewords(value, arg):
         length = int(arg)
     except ValueError: # Invalid literal for int().
         return value # Fail silently.
-    return truncate_words(value, length)
+    return Truncator(value).words(length, truncate=' ...')
 truncatewords.is_safe = True
 truncatewords = stringfilter(truncatewords)
 
@@ -272,7 +286,7 @@ def truncatewords_html(value, arg):
         length = int(arg)
     except ValueError: # invalid literal for int()
         return value # Fail silently.
-    return truncate_html_words(value, length)
+    return Truncator(value).words(length, html=True, truncate=' ...')
 truncatewords_html.is_safe = True
 truncatewords_html = stringfilter(truncatewords_html)
 

django/utils/text.py

@@ -1,4 +1,6 @@
 import re
+import unicodedata
+import warnings
 from gzip import GzipFile
 from htmlentitydefs import name2codepoint
 
@@ -8,14 +10,18 @@ except ImportError:
     from StringIO import StringIO
 
 from django.utils.encoding import force_unicode
-from django.utils.functional import allow_lazy
+from django.utils.functional import allow_lazy, SimpleLazyObject
-from django.utils.translation import ugettext_lazy, ugettext as _
+from django.utils.translation import ugettext_lazy, ugettext as _, pgettext
-
 
 # Capitalizes the first letter of a string.
 capfirst = lambda x: x and force_unicode(x)[0].upper() + force_unicode(x)[1:]
 capfirst = allow_lazy(capfirst, unicode)
 
+# Set up regular expressions
+re_words = re.compile(r'&.*?;|<.*?>|(\w[\w-]*)', re.U)
+re_tag = re.compile(r'<(/)?([^ ]+?)(?: (/)| .*?)?>')
+
+
 def wrap(text, width):
     """
     A word-wrap function that preserves existing line breaks and most spaces in
@@ -44,46 +50,114 @@ def wrap(text, width):
     return u''.join(_generator())
 wrap = allow_lazy(wrap, unicode)
 
-def truncate_words(s, num, end_text='...'):
+
-    """Truncates a string after a certain number of words. Takes an optional
+class Truncator(SimpleLazyObject):
+    """
+    An object used to truncate text, either by characters or words.
+    """
+    def __init__(self, text):
+        super(Truncator, self).__init__(lambda: force_unicode(text))
+
+    def add_truncation_text(self, text, truncate=None):
+        if truncate is None:
+            truncate = pgettext(
+                'String to return when truncating text',
+                u'%(truncated_text)s...')
+        truncate = force_unicode(truncate)
+        if '%(truncated_text)s' in truncate:
+            return truncate % {'truncated_text': text}
+        # The truncation text didn't contain the %(truncated_text)s string
+        # replacement argument so just append it to the text.
+        if text.endswith(truncate):
+            # But don't append the truncation text if the current text already
+            # ends in this.
+            return text
+        return '%s%s' % (text, truncate)
+
+    def chars(self, num, truncate=None):
+        """
+        Returns the text truncated to be no longer than the specified number
+        of characters.
+
+        Takes an optional argument of what should be used to notify that the
+        string has been truncated, defaulting to a translatable string of an
+        ellipsis (...).
+        """
+        length = int(num)
+        text = unicodedata.normalize('NFC', self._wrapped)
+
+        # Calculate the length to truncate to (max length - end_text length)
+        truncate_len = length
+        for char in self.add_truncation_text('', truncate):
+            if not unicodedata.combining(char):
+                truncate_len -= 1
+                if truncate_len == 0:
+                    break
+
+        s_len = 0
+        end_index = None
+        for i, char in enumerate(text):
+            if unicodedata.combining(char):
+                # Don't consider combining characters
+                # as adding to the string length
+                continue
+            s_len += 1
+            if end_index is None and s_len > truncate_len:
+                end_index = i
+            if s_len > length:
+                # Return the truncated string
+                return self.add_truncation_text(text[:end_index or 0],
+                                                truncate)
+
+        # Return the original string since no truncation was necessary
+        return text
+    chars = allow_lazy(chars)
+
+    def words(self, num, truncate=None, html=False):
+        """
+        Truncates a string after a certain number of words. Takes an optional
         argument of what should be used to notify that the string has been
-    truncated, defaulting to ellipsis (...)
+        truncated, defaulting to ellipsis (...).
+        """
+        length = int(num)
+        if html:
+            return self._html_words(length, truncate)
+        return self._text_words(length, truncate)
+    words = allow_lazy(words)
+
+    def _text_words(self, length, truncate):
+        """
+        Truncates a string after a certain number of words.
 
         Newlines in the string will be stripped.
         """
-    s = force_unicode(s)
+        words = self._wrapped.split()
-    length = int(num)
-    words = s.split()
         if len(words) > length:
             words = words[:length]
-        if not words[-1].endswith(end_text):
+            return self.add_truncation_text(u' '.join(words), truncate)
-            words.append(end_text)
         return u' '.join(words)
-truncate_words = allow_lazy(truncate_words, unicode)
 
-def truncate_html_words(s, num, end_text='...'):
+    def _html_words(self, length, truncate):
-    """Truncates HTML to a certain number of words (not counting tags and
+        """
-    comments). Closes opened tags if they were correctly closed in the given
+        Truncates HTML to a certain number of words (not counting tags and
-    html. Takes an optional argument of what should be used to notify that the
+        comments). Closes opened tags if they were correctly closed in the
-    string has been truncated, defaulting to ellipsis (...).
+        given HTML.
 
         Newlines in the HTML are preserved.
         """
-    s = force_unicode(s)
-    length = int(num)
         if length <= 0:
             return u''
-    html4_singlets = ('br', 'col', 'link', 'base', 'img', 'param', 'area', 'hr', 'input')
+        html4_singlets = (
-    # Set up regular expressions
+            'br', 'col', 'link', 'base', 'img',
-    re_words = re.compile(r'&.*?;|<.*?>|(\w[\w-]*)', re.U)
+            'param', 'area', 'hr', 'input'
-    re_tag = re.compile(r'<(/)?([^ ]+?)(?: (/)| .*?)?>')
+        )
         # Count non-HTML words and keep note of open tags
         pos = 0
         end_text_pos = 0
         words = 0
         open_tags = []
         while words <= length:
-        m = re_words.search(s, pos)
+            m = re_words.search(self._wrapped, pos)
             if not m:
                 # Checked through whole string
                 break
@@ -100,7 +174,8 @@ def truncate_html_words(s, num, end_text='...'):
                 # Don't worry about non tags or tags after our truncate point
                 continue
             closing_tag, tagname, self_closing = tag.groups()
-        tagname = tagname.lower()  # Element names are always case-insensitive
+            # Element names are always case-insensitive
+            tagname = tagname.lower()
             if self_closing or tagname in html4_singlets:
                 pass
             elif closing_tag:
@@ -110,22 +185,37 @@ def truncate_html_words(s, num, end_text='...'):
                 except ValueError:
                     pass
                 else:
-                # SGML: An end tag closes, back to the matching start tag, all unclosed intervening start tags with omitted end tags
+                    # SGML: An end tag closes, back to the matching start tag,
-                open_tags = open_tags[i+1:]
+                    # all unclosed intervening start tags with omitted end tags
+                    open_tags = open_tags[i + 1:]
             else:
                 # Add it to the start of the open tags list
                 open_tags.insert(0, tagname)
         if words <= length:
             # Don't try to close tags if we don't need to truncate
-        return s
+            return self._wrapped
-    out = s[:end_text_pos]
+        out = self._wrapped[:end_text_pos]
-    if end_text:
+        truncate_text = self.add_truncation_text('', truncate)
-        out += ' ' + end_text
+        if truncate_text:
+            out += truncate_text
         # Close any tags still open
         for tag in open_tags:
             out += '</%s>' % tag
         # Return string
         return out
+
+def truncate_words(s, num, end_text='...'):
+    warnings.warn('This function has been deprecated. Use the Truncator class '
+        'in django.utils.text instead.', category=PendingDeprecationWarning)
+    truncate = end_text and ' %s' % end_text or ''
+    return Truncator(s).words(num, truncate=truncate)
+truncate_words = allow_lazy(truncate_words, unicode)
+
+def truncate_html_words(s, num, end_text='...'):
+    warnings.warn('This function has been deprecated. Use the Truncator class '
+        'in django.utils.text instead.', category=PendingDeprecationWarning)
+    truncate = end_text and ' %s' % end_text or ''
+    return Truncator(s).words(num, truncate=truncate, html=True)
 truncate_html_words = allow_lazy(truncate_html_words, unicode)
 
 def get_valid_filename(s):

docs/internals/deprecation.txt

@@ -220,6 +220,12 @@ their deprecation, as per the :ref:`Django deprecation policy
           was deprecated since Django 1.4 and will be removed in favor of the
           generic static files handling.
 
+        * The builin truncation functions
+          :func:`django.utils.text.truncate_words` and
+          :func:`django.utils.text.truncate_html_words`
+          were deprecated since Django 1.4 and will be removed in favor
+          of the ``django.utils.text.Truncator`` class.
+
     * 2.0
         * ``django.views.defaults.shortcut()``. This function has been moved
           to ``django.contrib.contenttypes.views.shortcut()`` as part of the

docs/ref/templates/builtins.txt

@@ -2055,6 +2055,24 @@ For example::
 
 If ``value`` is ``"my first post"``, the output will be ``"My First Post"``.
 
+.. templatefilter:: truncatechars
+
+truncatechars
+^^^^^^^^^^^^^
+
+.. versionadded:: 1.4
+
+Truncates a string if it is longer than the specified number of characters.
+Truncated strings will end with a translatable ellipsis sequence ("...").
+
+**Argument:** Number of characters to truncate to
+
+For example::
+
+    {{ value|truncatechars:9 }}
+
+If ``value`` is ``"Joel is a slug"``, the output will be ``"Joel i..."``.
+
 .. templatefilter:: truncatewords
 
 truncatewords

docs/releases/1.4.txt

@@ -145,6 +145,14 @@ A new helper function,
 ``template.Library`` to ease the creation of template tags that store some
 data in a specified context variable.
 
+``truncatechars`` template filter
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Added a filter which truncates a string to be no longer than the specified
+number of characters. Truncated strings end with a translatable ellipsis
+sequence ("..."). See the :tfilter:`truncatechars docs <truncatechars>` for
+more details.
+
 CSRF improvements
 ~~~~~~~~~~~~~~~~~
 

tests/regressiontests/utils/text.py

@@ -1,10 +1,69 @@
+# -*- coding: utf-8 -*-
 import unittest
 
 from django.utils import text
 
 class TestUtilsText(unittest.TestCase):
 
+    def test_truncate_chars(self):
+        truncator = text.Truncator(
+            u'The quick brown fox jumped over the lazy dog.'
+        )
+        self.assertEqual(u'The quick brown fox jumped over the lazy dog.',
+            truncator.chars(100)),
+        self.assertEqual(u'The quick brown fox ...',
+            truncator.chars(23)),
+        self.assertEqual(u'The quick brown fo.....',
+            truncator.chars(23, '.....')),
+
+        # Ensure that we normalize our unicode data first
+        nfc = text.Truncator(u'o\xfco\xfco\xfco\xfc')
+        nfd = text.Truncator(u'ou\u0308ou\u0308ou\u0308ou\u0308')
+        self.assertEqual(u'oüoüoüoü', nfc.chars(8))
+        self.assertEqual(u'oüoüoüoü', nfd.chars(8))
+        self.assertEqual(u'oü...', nfc.chars(5))
+        self.assertEqual(u'oü...', nfd.chars(5))
+
+        # Ensure the final length is calculated correctly when there are
+        # combining characters with no precomposed form, and that combining
+        # characters are not split up.
+        truncator = text.Truncator(u'-B\u030AB\u030A----8')
+        self.assertEqual(u'-B\u030A...', truncator.chars(5))
+        self.assertEqual(u'-B\u030AB\u030A-...', truncator.chars(7))
+        self.assertEqual(u'-B\u030AB\u030A----8', truncator.chars(8))
+
+        # Ensure the length of the end text is correctly calculated when it
+        # contains combining characters with no precomposed form.
+        truncator = text.Truncator(u'-----')
+        self.assertEqual(u'---B\u030A', truncator.chars(4, u'B\u030A'))
+        self.assertEqual(u'-----', truncator.chars(5, u'B\u030A'))
+
+        # Make a best effort to shorten to the desired length, but requesting
+        # a length shorter than the ellipsis shouldn't break
+        self.assertEqual(u'...', text.Truncator(u'asdf').chars(1))
+
     def test_truncate_words(self):
+        truncator = text.Truncator(u'The quick brown fox jumped over the lazy '
+            'dog.')
+        self.assertEqual(u'The quick brown fox jumped over the lazy dog.',
+            truncator.words(10))
+        self.assertEqual(u'The quick brown fox...', truncator.words(4))
+        self.assertEqual(u'The quick brown fox[snip]',
+            truncator.words(4, '[snip]'))
+
+    def test_truncate_html_words(self):
+        truncator = text.Truncator('<p><strong><em>The quick brown fox jumped '
+            'over the lazy dog.</em></strong></p>')
+        self.assertEqual(u'<p><strong><em>The quick brown fox jumped over the '
+            'lazy dog.</em></strong></p>', truncator.words(10, html=True))
+        self.assertEqual(u'<p><strong><em>The quick brown fox...</em>'
+            '</strong></p>', truncator.words(4, html=True))
+        self.assertEqual(u'<p><strong><em>The quick brown fox....</em>'
+            '</strong></p>', truncator.words(4, '....', html=True))
+        self.assertEqual(u'<p><strong><em>The quick brown fox</em></strong>'
+            '</p>', truncator.words(4, '', html=True))
+
+    def test_old_truncate_words(self):
         self.assertEqual(u'The quick brown fox jumped over the lazy dog.',
             text.truncate_words(u'The quick brown fox jumped over the lazy dog.', 10))
         self.assertEqual(u'The quick brown fox ...',
@@ -12,7 +71,7 @@ class TestUtilsText(unittest.TestCase):
         self.assertEqual(u'The quick brown fox ....',
             text.truncate_words('The quick brown fox jumped over the lazy dog.', 4, '....'))
 
-    def test_truncate_html_words(self):
+    def test_old_truncate_html_words(self):
         self.assertEqual(u'<p><strong><em>The quick brown fox jumped over the lazy dog.</em></strong></p>',
             text.truncate_html_words('<p><strong><em>The quick brown fox jumped over the lazy dog.</em></strong></p>', 10))
         self.assertEqual(u'<p><strong><em>The quick brown fox ...</em></strong></p>',