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{% translate s %} passed in {% include ... with s=s %} not in .po file

I have a basic feed I am trying to render in my Django project. I have created a feed.html file as a base template for slight variations of the same type of feed. Among those variations, is the header of the feed. Importantly, I want that header to be translated into multiple languages.
I have implemented this "variation" idea using {% include "feed.html" with variation=variation %}. However, I am having problems translating those variations.
I am trying the following in feed.html:
{% translate header %}
Then in one of the templates where I want a variation of feed.html I have:
{% include "feed.html" with header="Header" %}
The problem is, the string "Header" does not make it into any of my .po files and therefore remains untranslatable.
What am I doing wrong? Should I use different syntax?

The problem is, the string "Header" does not make it into any of my .po files and therefore remains untranslatable.
If that means that the makemessages command doesn't extract the string, then yes, it won't, because there is no string. Only a variable. That variable could take any value at all, makemessages cannot possibly trace that back to all possible locations where you might be setting the value for header. makemessages can only extract what you literally put into {% translate %} tags or _() function calls directly.
The caveat with using variables or computed values, as in the previous two examples, is that Django’s translation-string-detecting utility, django-admin makemessages, won’t be able to find these strings.
https://docs.djangoproject.com/en/3.1/topics/i18n/translation/#standard-translation
You'll want to translate the header value before passing it:
{% include "feed.html" with header=_("Header") %}

How to protect some files from the Jinja template processor?

I am using cookiecutter to create a tornado project, using this template (it has several bugs, so you'll probably won't be able to use it out of the box). I have hit a problem which I do not know how to solve:
jinja2.exceptions.TemplateSyntaxError: unexpected char '\\' at 124272
File "./{{cookiecutter.project_slug}}/static/swagger/lib/jsoneditor.min.js", line 10
I am not sure, but I have the impression that cookiecutter is trying to Jinja-process the jsoneditor.min.js, which is not supposed to happen, since the "templating" in that file is not supposed to be processed by cookiecutter, it just happens to include the same escape characters that Jinja is using.
Is it possible to tell cookiecutter not to process files inside a certain directory? This is probably a matter of properly setting up the cookiecutter template, but not sure how this can be specified.

By default cookiecutter will try to process every file as a jinja template which produces wrong results if you have something that looks like a jinja template but is only supposed to be taken literal. Starting with cookiecutter 1.1 one can tell cookiecutter to only copy some files without interpreting them as jinja template (documentation).
To do that you have to add a _copy_without_render key in the cookiecutter config file (cookiecutter.json). It takes a list of regular expressions. If a filename matches the regular expressions it will be copied and not processed as a jinja template.
Example
{
"project_slug": "sample",
"_copy_without_render": [
"*.js",
"not_rendered_dir/*",
"rendered_dir/not_rendered_file.ini"
]
}
This will not process any javascript files (files which end with .js), any files that are in the not_rendered_dir and not the not_rendered_file.ini in the rendered_dir. They will only get copied.

Just came across this question and also this Github Issue.
It seems like a nice addition, that one can partially mark parts of a file or entire template to not be processed by using the {% raw %} tag:
{% raw %}
{% comment %}Whatever jinja code goes here....{% endcomment %}
...
{% endraw %}

Django templates and whitespace

I started using custom inclusion tags within my django templates. For example I have a {% profilelink profile %} tag that inserts a link to a user profile together with a small version of the profile's picture, like so (profilelink.html):
<a href='{% url ... %}'><img src='{{ ... }}' alt='...'> {{ profile.name }}</a>
However, when I use it in the following snippet (sometemplate.html):
<p>Owned by {% profilelink owner %} (uploaded by {% profilelink uploader %})</p>
Then I get whitespace between the HTML produced by the second template tag and the closing parenthesis. This whitespace is unwanted. It comes from the final newline character in the file profilelink.html. This is a very common problem and searching Stackoverflow yields a lot of questions about whitespace in templates in general. Here's a summary of solutions found so far and why they don't work:
Some of these problems are solvable with the {% spaceless %} tag, but not all of them. This tag only removes whitespace between tags, which is not the case in the above example.
One possible solution is to not have a final EOL in profilelink.html but that's highly undesirable. Reasons: It is generally bad style; some editors (vim) silently add one back by default; that's how POSIX defines a line; it might make some SCMs unhappy; etc.
Another solution is switching to another template engine, like Jinja2, which may or may not solve this problem. It has support for constructs like {% ... -%} which eat the next EOL character. This is useful in some situations, but is also useless for my example above. But switching the templating backend for such a small annoyance seems a little overkill and adds another dependency. I'd like to stick to whatever is the standard "django" way of doing things. There are apparently plans to make Jinja2 the new Django default, though.
Some people suggested using a middleware class to remove redundant whitespace from the generated HTML before it's being sent to the browser. This is useful, but only for transforming the HTML in a way that is functionally equivalent, i.e. same semantics: it will then still be displayed the same way in the browser. That's not what I want, I want an actual change in semantics in order to have it display properly. This is impossible to implement in a generic middleware class. I need to have control over this on a case by case basis from within the template itself. I don't care about making the HTML prettier, I care about it being correct in the first place.
There's also bug #2594 which has been closed as WONTFIX with the argument (quote) "the Django template language is good enough for generating HTML, which isn't sensitive to whitespace". In my oponion this is just totally wrong. HTML is very much sensitive to whitespace, it just doesn't care how much there is of it. It cares a lot about whether there is some whitespace or none at all.
Some my question is: Is there any sane way to fix this problem in general? (One that always works, not just in some situations.)
(Any CSS-based fixes do not count. Copy/paste surprises are evil.)

I believe one solution is to use a simple_tag instead of an inclusion tag, hopefully without to much clutter.
I assume your tag is something like this:
#register.inclusion_tag('profilelink.html')
def profilelink(user):
return {"profile": user}
Would it be possible to substitute this with
from django.template.loader import render_to_string
#register.simple_tag
def profilelink(user):
t = render_to_string("profilelink.html", {"profile": user})
return t.strip()
I don't have a Django-project in front of me now, so this is untested.

This is the best I came up with so far. I still hope for a better solution, but for now it will do.
I defined a custom filter like this in base/templatetags/basetags.yp (taken from this answer):
from django import template
from django.template.defaultfilters import stringfilter
register = template.Library()
#register.filter
#stringfilter
def trim(value):
return value.strip()
And then use it as follows:
{% load basetags %}
<p>Owned by {% profilelink owner %} (uploaded by
{% filter trim %}{% profilelink uploader %}{% endfilter %})</p>

Why can't iterate through this list in a Django template

I have a variable from my view that is the output of a Model.objects.all() call on that Model. I'm passing it to my template in my view, and I'm trying to iterate over it in the template. I can access the first element of it simply by this line of code. 'code' is the name of a field in my django model. This line does print the first element's 'code' attribute correctly.
{{ var_name.0.code }}
However, when I try to iterate over var_name in a template for loop, nothing shows up. I tried the following code:
{% for single_var in var_name %}
{{ single_var.code }}
{% endfor %}
This isn't actually what I want to do in the for loop, but getting this to work will let me do what I need in the template. It may be noteworthy to add that at the moment this list has only one element in it.
This is for a work project, so that's why I changed the variable names to something generic.

I found that changing the name of single_var to something without an underscore seemed to fix it. This doesn't make a lot of sense to me because the Django template language documentation states the following:
Variable names consist of any combination of alphanumeric characters and the underscore ("_").
Does anyone know why this seemed to fix the problem?

Jinja2 - Given 2 templates (as strings) how to render one that extends the other?

I'm making a simple script that works on Jinja2 templates. Right now it's just reading files in from disk manually, i.e. no Jinja Loaders. I have 2 strings (A and B), representing 2 templates. I want to make one template (B) inherit from the other (A), i.e. I have {% block body %}{% endblock %} in A, and I want to make the body block be the contents of B. How can I get the rendered output of this?
Normally I'd use {% extends 'filename' %} in B and it'd use the right one, however I don't have the filename (per se) for A.

Your best bet probably to use a different template loader. Take a look at DictLoader and FunctionLoader, or try your hand a writing your own template loader.