Better error when a state includes salt['foo.bar'] without ()

[SEJeff]

Example naiive state:

{% if 'jeff' in salt['user.list_users'] %}
/tmp/jeff-is-here.txt:
  file.touch
{% endif %}

Completely unobvious (to a non-developer) error when running state.highstate:

local:
    Data failed to compile:
----------
    Rendering SLS dev.salt failed, render error:
Traceback (most recent call last):
  File "/home/jeff/git/salt/salt/utils/templates.py", line 54, in render_tmpl
    output = render_str(tmplstr, context, tmplpath)
  File "/home/jeff/git/salt/salt/utils/templates.py", line 94, in render_jinja_tmpl
    output = jinja_env.from_string(tmplstr).render(**context)
  File "/usr/lib/python2.7/site-packages/jinja2/environment.py", line 894, in render
    return self.environment.handle_exception(exc_info, True)
  File "<template>", line 25, in top-level template code
TypeError: argument of type 'function' is not iterable

I am aware that the correct state is the same as above but the first line should look like:

{% if 'jeff' in salt['user.list_users']() %}

However, this is a simple mistake and we should try (if possible) to present a more obvious and friendly error message. This was found while testing out #3028

[thatch45]

Yes, this is tricky, since this is going down the path of catching a bunch of specific templating errors. but catching the common ones would be a good idea

[SEJeff]

Perhaps there is somewhere in the code you can do something like if callable(fun) error: You need to call the function with parenthesis? I'm unsure if this would require subclassing the renderer or could be done elsewhere in the stack? Perhaps it could be done in templates.py? I want to believe this isn't that hard.

[stale]

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