Plone 5.2 - HTML Dublin Core Behavior for Plone. Meant to replace plone.dublincore. Honors HTML filtering, and saves a plain text version of the value to the default Title and Description, so you don't have to override dozens of templates in your site

metadata.py

import re
import six

from plone.app.dexterity import _
from plone.app.dexterity.behaviors.metadata import (
    MetadataBase,
    ICategorization,
    Categorization,
    IPublication,
    Publication,
    IOwnership,
    Ownership)
from plone.autoform import directives
from plone.autoform.interfaces import IFormFieldProvider
from plone.supermodel import model
from Products.PortalTransforms.transforms.safe_html import SafeHTML
from z3c.form.interfaces import IAddForm, IEditForm
from zope import schema
from zope.interface import provider


@provider(IFormFieldProvider)
class IHTMLBasic(model.Schema):

    html_title = schema.TextLine(
        title=_(u'label_title', default=u'Title'),
        required=True
    )

    html_description = schema.Text(
        title=_(u'label_description', default=u'Summary'),
        description=_(
            u'help_description',
            default=u'Used in item listings and search results.'
        ),
        required=False,
        missing_value=u'',
    )

    directives.order_before(html_description='*')
    directives.order_before(html_title='*')

    directives.no_omit(IEditForm, 'html_title', 'html_description')
    directives.no_omit(IAddForm, 'html_title', 'html_description')


class HTMLBasic(MetadataBase):
    """Clean the HTML title and description
       and set regular Title and Description without HTML
    """

    def _get_html_title(self):
        return self.context.html_title

    def cleanhtml(self, raw_html):
        cleanr = re.compile('<.*?>')
        cleanhtml = re.compile('&.*?;')
        cleantext = re.sub(cleanr, '', raw_html)
        cleantext = re.sub(cleanhtml, '', cleantext)
        return cleantext

    def _set_html_title(self, value):
        if not value:
            self.context.title = ''
            return
        if not isinstance(value, six.text_type):
            raise ValueError('Title must be text.')
        scrubbed_value = self.transform.scrub_html(value)
        self.context.html_title = scrubbed_value
        self.context.title = self.cleanhtml(scrubbed_value)
    html_title = property(_get_html_title, _set_html_title)

    def _get_html_description(self):
        return self.context.html_description

    def _set_html_description(self, value):
        if not value:
            self.context.description = ''
            return
        if not isinstance(value, six.text_type):
            raise ValueError('Description must be text.')
        scrubbed_value = self.transform.scrub_html(value)
        self.context.html_description = scrubbed_value
        self.context.description = self.cleanhtml(scrubbed_value)
    html_description = property(_get_html_description, _set_html_description)

    def __init__(self, *args, **kwargs):
        super(HTMLBasic, self).__init__(*args, **kwargs)
        self.transform = SafeHTML()


@provider(IFormFieldProvider)
class IHTMLDublinCore(IOwnership, IPublication, ICategorization, IHTMLBasic):
    """ Metadata behavior providing all the DC fields
    """
    pass


class HTMLDublinCore(HTMLBasic, Categorization, Publication, Ownership):
    pass

Products.CMFPlone.browser.templates.description.pt

<div class="documentDescription description"
    tal:define="html_descrip context/html_description | nothing;
                plain_descrip context/Description"
    tal:condition="plain_descrip">
    <tal:html tal:condition="html_descrip"
              tal:content="structure html_descrip">
        Description
    </tal:html>
    <tal:plain tal:condition="not: html_descrip"
               tal:content="plain_descrip">
        Description
    </tal:plain>
</div>

Products.CMFPlone.browser.templates.title.pt

<h1 class="documentFirstHeading"
    tal:define="html_title context/html_title | nothing;
                plain_title context/Title"
    tal:condition="plain_title">
    <tal:html tal:condition="html_title"
              tal:content="structure html_title">
          Title or id
    </tal:html>
    <tal:plain tal:condition="not: html_title"
               tal:content="plain_title">
          Title or id
    </tal:plain>
</h1>