using Django "include" template tag as nested - side effects?

Question

Does anyone know or have any experience about bad side effects of using "nested include tags"? (I mean including a template file which itself includes another template)

For example:

file x.html:

{% include "z.html" %}

file y.html:

{% inclide "x.html" %}

score 2 · Accepted Answer · edited Jan 10 '22 at 00:44

Bad side effects are messed up CSS rules and some headache while debugging. It is generally better to keep them rather flat.

x.html:

{% extends "_base.html" %}

{% block main_content %}
    <h1>I am X</h1>

    {% include "includes/z.html" %}
    
{% endblock main_content %}

y.html:

{% block main_content %}
    <h1>I am Y</h1>

    {% include "x.html" %}
    
{% endblock main_content %}

z.html:

<h2>I am Z</h2>

Check the code: https://github.com/almazkun/templating

Swift · Answer 2 · 2022-01-10T21:59:35.953

I think you are confusing include and extends

Logically, extending a template when used in the likes of a base.html is great, and if you design your templates in a way which allows you to extend certain base html files for certain sections of your site. This is generally when they have shared snippets of html, like the main css block, meta block, script block etc..

You can extend n number of times.

Where you are getting confused with include, is that this is more for including snippets of code which are additive or sort of "drop-in" and great examples would be sidebars, navbars, and even custom css or javascript!

The question is, do you want to shared html snippets, or do you want to add extra snippets to certain sections but not others?

If its the latter, you'll want include, and for the former, you'll want extends.

Edit #1: You have asked for clarity regarding the drawbacks of the two aforementioned template tags. As I sit here and ponder that question, I cant think of any significant disadvantages of using either include or extends providing that you have used them where they should be used. If you have used an include, where actually you should have used extended the template, you may find, as is described in someone else's answer, that css rules may not be applied in the way you would expect them to be.

Really useful points. Thanks for them. But anyway I also want to know the bad consequences too — muel, Jan 10 '22 at 20:11
Added an edit, sorry I can't be more helpful with this point. — Swift, Jan 10 '22 at 22:00

raratiru · Answer 3 · 2022-05-05T10:30:34.020

The question is about nested include tags and the answers show that "there is no actual problem if you know what you expect and how to handle it".

There is a paragraph in the docs about the include tag that sets some limits, nonetheless:

The include tag should be considered as an implementation of “render this subtemplate and include the HTML”, not as “parse this subtemplate and include its contents as if it were part of the parent”. This means that there is no shared state between included templates – each include is a completely independent rendering process.

Trying to make ends meet about rendering and parsing: https://stackoverflow.com/a/35966477/2996101
Shared state between included templates is a complicated issue even for big front end frameworks, such as React.

score 0 · Answer 4 · answered Oct 11 '21 at 21:34

0

No problem! It's usual to use inheritance in Django templates. You can make a template with some blocks and override blocks in children templates and children of children can override or use superblock content.

answered Oct 11 '21 at 21:34

mrash

883
7
18

Thank you for your suggestions, dear friend. I know these substitute ways. My question is another thing. – muel Oct 12 '21 at 06:01
can you explain? – mrash Oct 12 '21 at 06:40
explained above in the post, the best way possible. pls read again... – muel Oct 12 '21 at 13:39

score 0 · Answer 5 · answered Jan 05 '22 at 22:51

0

I didn't have any issues chaining include. You might have issues if have extend or blocks with similar names in the included template.

answered Jan 05 '22 at 22:51

Jon Mathew

1

score 0 · Answer 6 · answered Jan 07 '22 at 06:32

There are no issues when you include a number of templates.

for example base.html

<!doctype html>
<html lang="en">
  <head>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <!-- Bootstrap CSS -->
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-1BmE4kWBq78iYhFldvKuhfTAU6auU8tT94WrHftjDbrCEXSU1oBoqyl2QvZ6jIW3" crossorigin="anonymous">

    {% block title %}{% endblock %}
  </head>
  <body>
    {% block content %}
    {% endblock %}

    <!-- Optional JavaScript; choose one of the two! -->

    <!-- Option 1: Bootstrap Bundle with Popper -->
    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.bundle.min.js" integrity="sha384-ka7Sk0Gln4gmtz2MlQnikT1wXgYsOg+OMhuP+IlRH9sENBO0LRn5q+8nbTov4+1p" crossorigin="anonymous"></script>

    <!-- Option 2: Separate Popper and Bootstrap JS -->
    <!--
    <script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.10.2/dist/umd/popper.min.js" integrity="sha384-7+zCNj/IqJ95wo16oMtfsKbZ9ccEh31eOz1HGyDuCQ6wgnyJNSYdrPa03rtR1zdB" crossorigin="anonymous"></script>
    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.1.3/dist/js/bootstrap.min.js" integrity="sha384-QJHtvGhmr9XOIpI6YVutG+2QOK9T+ZnN4kzFN1RtK3zEFEIsxhlmWl5/YESvpZ13" crossorigin="anonymous"></script>
    -->
  </body>
</html>

a.html

<h1>I am from A</h1>

b.html

<h2>I am from B</h2>

c.html

{% extends 'base.html' %}
{% load static %}
{% block title %}<title>Welcome in C!</title>{% endblock %}
<h3>I am from C . I am mother of A and B </h3>
{% block content %}
{% include 'a.html' %}
{% include 'b.html' %}
{% endblock %}

using Django "include" template tag as nested - side effects?

6 Answers6