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Thursday, July 16, 2015
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Yesterday I started to worked on :ticket:`340` (Reception clerk sees
"Career" tab).

This problem was rather subtle and took me quite some hours of
investigation, mainly using the tested document
:ref:`welfare.specs.20150715`.

It was due to a bug in Lino.
:meth:`lino.modlib.extjs.ext_renderer.ExtRenderer.write_lino_js` used
to run a method `loosen_requirements` in the following lines::

    for e in lh.main.walk():
        e.loosen_requirements(res)

This was needed because we said that for example an InsertFormPanel
has initially the requirements of the actor who *defines* it. That
actor may not be visible to the current user.  But the panel may be
used by other actors which are visible because they have less
requirements. So there are panel for which we need to generate a JS
code definition even though the actor who defines them is not
available.

But the old approach modified the global element tree.  This caused
the described side effect.  As long as this process didn't run,
everything was okay. 

So I replaced it by a different approach: the individual elements no
longer inherit the `required_roles` of their actor, and we have a new
attribute `_other_datasources` on every
:class:`lino.core.layouts.BaseLayout` instance in order to decide
whether the code is to be included in that profile's `lino*.js` file
or not.

Fixing this unveiled also a minor problem of plugin interdependency
(:mod:`lino.modlib.system` needs :mod:`lino.modlib.printing` or so).