assets_include works intermittently in imported file

[rsyring]

My template landing.html started like:

{% set title = space.name + ' Collaborative' %}
{% import '_resources.html' as res_macros %}
{% extends "collab-base-sidebar.html" %}

• _resources.html had some macros that were used and assets_include at the top of it
• _resources.css had some css that was needed by the macros

I observed that the content from _resources.css only made it into the page immediately after saving landing.html, presumably due to the process/server restart triggered by the file modification. On subsequent browser refreshes, the content was absent.

[guruofgentoo]

The reason this happens is due to Jinja caching imports:

• The first time the import is referenced, Jinja will parse the target template file.
• Our extension turns the assets_include on that first parse into a call block that will produce the expected content
• After that first load, Jinja caches the import and doesn't parse it again. But, I think what Jinja caches is the original template, not the version where we've patched in a call block
• Since it's cached at that point and not parsed again, we don't get to re-insert that call block and pull in the assets files

Not sure there's a clean way around this without coming up with a way to change how Jinja caches the import, or using a different approach to assets inclusion altogether.