analytics viewlet breaks if registry record is not defined

[ale-rt]

After #220 the fallback of returning an empty string if the webstat_js record was not found was removed.

That causes a rendering error:

zope.location.interfaces.LocationError: zope.location.interfaces.LocationError: (<Products.Five.browser.metaconfigure.View object at 0x7febfad14c50>, 'webstats_js')

 - Expression: "view/webstats_js"
 - Filename:   ... ayout-3.4.0-py3.7.egg/plone/app/layout/analytics/view.pt
 - Location:   (line 3: col 17)
 - Source:     tal:condition="view/webstats_js"
                              ^^^^^^^^^^^^^^^^

[ale-rt]

Actually that was added to the init:
https://github.com/plone/plone.app.layout/pull/220/files#diff-341ad69d5b3785f1d3c5bf27f7a6f2f3R23

[mauritsvanrees]

This is still broken on coredev 5.2:

• Create a fresh Plone 5.2 site.
• View the front page and you see a traceback in the log.
• Go to the site control panel and add content to the webstats_js: no more traceback.
• Empty the webstats_js: traceback is back.

2020-02-05 16:43:18,785 ERROR   [plone.app.viewletmanager:118][waitress] Error while rendering viewlet-manager=plone.portalfooter, viewlet=plone.analytics
Traceback (most recent call last):
  File "/Users/maurits/shared-eggs/cp27m/plone.app.viewletmanager-3.1.0-py2.7.egg/plone/app/viewletmanager/manager.py", line 110, in render
    html.append(viewlet.render())
  File "/Users/maurits/shared-eggs/cp27m/Zope-4.1.3-py2.7.egg/Products/Five/browser/pagetemplatefile.py", line 126, in __call__
    return self.__func__(__self__, *args, **kw)
  File "/Users/maurits/shared-eggs/cp27m/Zope-4.1.3-py2.7.egg/Products/Five/browser/pagetemplatefile.py", line 61, in __call__
    sourceAnnotations=getattr(debug_flags, 'sourceAnnotations', 0),
  File "/Users/maurits/shared-eggs/cp27m/zope.pagetemplate-4.4.1-py2.7.egg/zope/pagetemplate/pagetemplate.py", line 135, in pt_render
    strictinsert=0, sourceAnnotations=sourceAnnotations
  File "/Users/maurits/shared-eggs/cp27m/Zope-4.1.3-py2.7.egg/Products/PageTemplates/engine.py", line 88, in __call__
    return self.template.render(**kwargs)
  File "/Users/maurits/shared-eggs/cp27m/z3c.pt-3.2.0-py2.7.egg/z3c/pt/pagetemplate.py", line 173, in render
    return base_renderer(**context)
  File "/Users/maurits/shared-eggs/cp27m/Chameleon-3.6.2-py2.7.egg/chameleon/zpt/template.py", line 306, in render
    return super(PageTemplate, self).render(**_kw)
  File "/Users/maurits/shared-eggs/cp27m/Chameleon-3.6.2-py2.7.egg/chameleon/template.py", line 209, in render
    raise_with_traceback(exc, tb)
  File "/Users/maurits/shared-eggs/cp27m/Chameleon-3.6.2-py2.7.egg/chameleon/template.py", line 187, in render
    self._render(stream, econtext, rcontext)
  File "/Users/maurits/community/plone-coredev/5.2/var/cache/8b517186501544b2072bbb30bc6d18a3.py", line 95, in render
    __condition = _static_4651129680(getitem('view'), econtext, True, ('webstats_js', ))
  File "/Users/maurits/shared-eggs/cp27m/Zope-4.1.3-py2.7.egg/Products/PageTemplates/expression.py", line 94, in __call__
    base = self.traverse(base, request, path_items)
  File "/Users/maurits/shared-eggs/cp27m/Zope-4.1.3-py2.7.egg/Products/PageTemplates/expression.py", line 65, in traverse
    base, name, path_items[i:], request=request
  File "/Users/maurits/shared-eggs/cp27m/zope.traversing-4.3.1-py2.7.egg/zope/traversing/adapters.py", line 156, in traversePathElement
    return traversable.traverse(nm, further_path)
  File "/Users/maurits/shared-eggs/cp27m/zope.traversing-4.3.1-py2.7.egg/zope/traversing/adapters.py", line 61, in traverse
    raise LocationError(subject, name)
LocationError: (<Products.Five.viewlet.metaconfigure.AnalyticsViewlet object at 0x11776dcd0>, 'webstats_js')

 - Expression: "view/webstats_js"
 - Filename:   ... /src/plone.app.layout/plone/app/layout/analytics/view.pt
 - Location:   (line 3: col 17)
 - Source:     tal:condition="view/webstats_js"
                              ^^^^^^^^^^^^^^^^
 - Arguments:  repeat: {...} (0)
               template: <ViewPageTemplateFile - at 0x113decbd0>
               views: <ViewMapper - at 0x11776df10>
               modules: <_SecureModuleImporter - at 0x10d637dd0>
               args: <tuple - at 0x10badf050>
               here: <ImplicitAcquisitionWrapper Plone at 0x115e01870>
               wrapped_repeat: <SafeMapping - at 0x117347440>
               user: <ImplicitAcquisitionWrapper - at 0x113db5b40>
               nothing: <NoneType - at 0x10b9f5718>
               container: <ImplicitAcquisitionWrapper Plone at 0x115e01870>
               request: <WSGIRequest - at 0x1177f3e10>
               traverse_subpath: <list - at 0x1172a4ef0>
               default: <object - at 0x10bb40e20>
               context: <ImplicitAcquisitionWrapper Plone at 0x115e01870>
               view: <AnalyticsViewlet plone.analytics at 0x11776dcd0>
               translate: <function translate at 0x1177cf230>
               root: <ImplicitAcquisitionWrapper  at 0x115e1b320>
               options: {...} (0)
               loop: {...} (0)
               target_language: <NoneType - at 0x10b9f5718>

Maybe update needs to be called before this line in plone.app.viewletmanager. But then why does it work when webstats_js has content?

[ale-rt]

Reverting this line should fix the issue:

• https://github.com/plone/plone.app.layout/pull/228/files#diff-341ad69d5b3785f1d3c5bf27f7a6f2f3L23

Anyway the sweetest thing would be making webstats_js a memoized property (thus lazy loading it only when needed without relying on update being called), but I feared at the time it was a breaking change.

[ale-rt]

I will try to investigate more and make a PR in the evening

[mauritsvanrees]

Making it a method should be enough I think, with @property. And instead of memoize it is easier to do a tal:define="webstats_js view/webstats_js" and then use webstats_js in the tal condition and content.

[ale-rt]

Funny enough yesterday I got a PR (plone/plone.app.testing#64) failing for this reason: https://jenkins.plone.org/job/pull-request-5.2-3.7/842/console