tal:define broken for variable self-reference

[Ross Patterson]

Using cmf.pt in a Plone 4 buildout, when a template does 'define="body_macro context/my_macros/macros/body;"' and then 'use-macro="context/base_edit/macros/master"', the tal:define in base_edit, "body_macro edit_macros/body | body_macro | base_macros/body;", gets the "base_macros/body" instead of the "body_macro" variable. If however, I add "XXX body_macro|nothing;", *right before* the body_macro tal:define in base_edit, then XXX *does* get the right macro.

When I manually change the define in base_edit to "body_macro edit_macros/body | XXX_body_macro | base_macros/body;" and then change the tal:define in my template to "XXX_body_macro", then the tal:define in base_edit gets the right macro for "body_macro".

So it seems that Chameleon doesn't handle self-reference in tal:define assignments correctly.

[Ross Patterson (rossp)]

I narrowed this down further. Variable self-reference actually only breaks when the self-reference is made in the second "else" ("|") clause in the expression. Attached is a patch adding test coverage that exposes this bug.

[Malthe Borch (mborch)]

It seems this is a problem with variables being carried over as part of dynamic scoping rules. This needs to be condensed into a simple (failing) test for us to continue solving it.

[Ross Patterson (rossp)]

Just in case you missed it, did you see the patch with test coverage exposing the bug I attached? Is it not "simple" enough? If not, how so?

[Ross Patterson (rossp)]

Looks like Malthe already committed the failing test, this is for my records.