Symfony and Twig: conditions in templates - php

Question

I have two bundles I created by my own: one to generate admin sections (AdminBundle), and another one to create bills (BillingBundle). BillingBundle has basically 2 entities: Client and Bill (1:m).
If I install both bundles to generate the new/edit forms and lists for Client and Bill at the admin, I include a part at config.yml like this:
my_admin_bundle:
entities:
project: #whatever entity. Project at AppBundle for example
new: true
list: true
client:
new: true
list: true
bill:
new: true
list: true
On the other hand, on AdminBundle I have a template called form.html.twig which renders the form to create new elements. Basically it is just like this:
{{ form(form) }}
The doubt: since the form to create new Bills need a .js file (accounting.js), how to include it only for new Bill form but not for new Client or Project forms ?
As you can imagine, now I have this in form.html.twig:
{{ form(form) }}
<script src="/bundles/ziiwebbilling/js/accounting.js" type="text/javascript"></script>
but I don't need accounting.js at form.html.twig for new Projects, or new Clients forms.
NOTE: sorry if I extend too much with my explanation, but I don't know how to explain it in another way. Even the title of the question is awful, please edit it if you find something better.
EDIT: as I've just wrote at the first comment for jkucharovic's answer, what I'm really looking for to solve my problem, is a non-intrusive way, that is: I wouldn't like to add the line about accounting.js inside an AdminBundle template. Or maybe am I looking for "too much"?

Answer 1

Use custom Twig extenstion with test function like this one:
public function getTests()
{
return [
new \Twig_SimpleTest('bill', function ($var) {
return $var instanceof Bill;
})
];
}
And then in template, you can simply test if form is for Bill entity:
{{ form(form) }}
{% if form.vars.value is bill %}
<script src="/bundles/ziiwebbilling/js/accounting.js"></script>
{% endif %}
Edit: If you don't want to modify template inside bundle for certain reason, you can make loading application-wide by defining own template and overriding default form block:
{%- block form -%}
{% if form.vars.value is bill %}
<script src="/bundles/ziiwebbilling/js/accounting.js"></script>
{% endif %}
{{ form_start(form) }}
{{- form_widget(form) -}}
{{ form_end(form) }}
{%- endblock form -%}