Django

Background As part of my ongoing project to reimplement Django’s templating language in Rust, I have been adding support for custom template tags. Simple tags The simplest custom tag will look something like: # time_tags.py from datetime import datetime from django import template register = template.Library() @register.simple_tag def time(format_string): now = datetime.now() return now.strftime(format_string) # time_tags.py from datetime import datetime from django import template register = template.Library() @register.simple_tag def current_time(format_string): return datetime.now().strftime(format_string) ...

Django Rusty Templates Since September 2024, I have been building a reimplementation of Django’s templating language in Rust, called Django Rusty Templates. During this process, I have discovered several weird edge-cases and bugs, some of which I’ve talked about before. Centring strings Django supports a template filter for centring strings: {{ "Django"|center:10 }} which adds padding around the string to reach the provided length. In this simple case, the template is rendered as ··Django·· (where · represents a space character). ...

Django Rusty Templates Since September 2024, I have been building a reimplementation of Django’s templating language in Rust, called Django Rusty Templates. During this process, I have discovered several weird edge-cases and bugs. Scientific notation Django supports writing floats in scientific notation (e.g. 6.28e23) in templates. However using a negative exponent was not supported: "{{ foo|default:5.2e-3 }}" Traceback (most recent call last): TemplateSyntaxError: Could not parse the remainder: '-3' from 'foo|default:5.2e-3' >>> from django.template.base import Template >>> Template("{{ foo|default:5.2e-3 }}") Traceback (most recent call last): ... raise TemplateSyntaxError( django.template.exceptions.TemplateSyntaxError: Could not parse the remainder: '-3' from 'foo|default:5.2e-3' ...