TAL Condition in Plone to hide HTML if it's a Document (Page)

I'm trying to modify my /portal_view_customizations/zope.interface.interface-plone.belowcontenttitle.documentbyline template with a tal expression, so that the document's author and the modification date do not show if the current portal type is a Document (Page). I don't mind if it shows for News Items, which are time sensitive, but not the Documents/Pages.

This is my failing Plone TAL expression:

<div class="documentByLine"
     id="plone-document-byline"
     i18n:domain="plone"
     tal:condition="view/show and not:python:here.portal_type == 'Document'"> 
...

I've also tried:

<div class="documentByLine"
     id="plone-document-byline"
     i18n:domain="plone"
     tal:condition="view/show and not:context/portal_type='Document'">

but still no luck. The tracebacks are pretty cryptic and don't relate to the TAL expression. However, if I get rid of my condition for portal_type, then it works again. Any thoughts are appreciated. A manual would be good, but I've looked at the official ones, and they don't mention this.

Solution

TAL's underlying TALES, the expression-engine of which TAL makes use of, doesn't support the mixing of expression-types in one expression. It's syntax allows only one expression-type to be specified (defaults to 'path', if omitted, btw), as no delimiter is provided (like a semicolon for chaining several TAL-statements in one element, e.g.).

But instead of mixing three expression-types you can use one python-expression, try:

python: view.show and context.portal_type()!='Document'

Update:

If you have customized a Plone's default-template via portal_view_customizations ('TTW'), now restricted python-methods cannot be accessed, that' why view/show throws an error.

It returns the allowAnonymousViewAbout-property of the site-properties, you can also check this condition yourself and your expression looks like:

tal:define="name user/getUserName" 
tal:condition="python:test(name!='Anonymous User') and context.portal_type()!='Document';

Quick'n'dirty alternative:

Do it with CSS:

body.userrole-anonymous .documentByLine {display:none}
body:not(.template-document_view) .documentByLine {display:block}

This will render the hidden elements, but it's helpful for prototyping and such, or 'quickfixes' (no admin available, etc.).