Extending Chameleon/five.pt

1

I'd love to extend Plone's templates as easily as I can in Django. At Chameleon level it seems easy, but the code below failed in a Plone's browser view, even though I made sure five.pt was a dependency in my build:

import ast
def uppercase_expression(string):
    def compiler(target, engine):
        uppercased = self.string.uppercase()
        value = ast.Str(uppercased)
        return [ast.Assign(targets=[target], value=value)]
    return compiler

  from chameleon import PageTemplate
  PageTemplate.expression_types['upper'] = uppercase_expression

In my template I have:

<div tal:content="upper:'mystring';" />

Which fails with:

Compilation failed
exceptions.LookupError: Unknown expression type: u'upper'

Is extending possible/should I look somewhere else? I'm running Plone 4 but the same happens in 5.

PS: I know this simple example can be implemented with a view method, allow_module or even a simple python: expression but template extendibility is a nice selling point and may be useful for other usecases.

2

I've got no idea for the answer, but did you try sticking PDB in your template as mentioned here?

3

Actually, that is no longer possible when you have the April hotfix installed.
See https://plone.org/security/hotfix/20160419/bypass-restricted-python

1 Like
4

What a pity. I agree this should be avoided for Restricted Python but not in filesystem code.

5

Oh, right, there is a difference. I forgot. In file system templates it should actually still work.
Or rather: in Zope 3 templates it should work, in Zope 2 templates not.

This means: in browser views, viewlets, and portlets you can use this. In skin templates, templates in portal_skins/custom, portal_view_customizations and templates in for example PloneFormGen overrides you cannot use this.