django-fastdev

django-fastdev is an app that makes it safer, faster and more fun to develop Django apps.

Features

Error on non-existent template variables

Django templates by default hide errors, and when it does show an error it\'s often not very helpful. This app changes this behavior to provide more informative error messages. For example, if you use:

{{ does_not_exist }}

instead of rendering that as an empty string, this app will raise a FastDevVariableDoesNotExist error with a detailed message:

does_not_exist does not exist in context. Available top level variables:

    DEFAULT_MESSAGE_LEVELS
    False
    None
    True
    bar
    csrf_token
    foo
    messages
    perms
    request
    user

There are more specialized error messages for accessing non-existent keys in a dict or attributes of an object several levels deep, such as foo.bar.baz (where baz doesn\'t exist).

Handling `default` and `default_if_none` Filters

When using the default or default_if_none filters, django-fastdev will not raise an exception for non-existent variables. Instead, it behaves as one might intuitively expect by populating the context variable with the result of the filter operation. For example:

{{ does_not_exist|default:"N/A" }}
{{ does_not_exist|default_if_none:"" }}

In these cases:

If does_not_exist is undefined, default:"N/A" will render as N/A, and default_if_none:"" will render as an empty string ("").
This ensures that templates using these filters handle missing variables gracefully, aligning with Django\'s built-in behavior while maintaining django-fastdev\'s strict checking for other cases.

By default, django-fastdev only checks templates that exist within your project directory. To check ALL templates, including stock Django templates and templates from third-party libraries, add FASTDEV_STRICT_TEMPLATE_CHECKING = True to your project settings.py.

Improved TemplateDoesNotExist errors

Good suggestions for what you wanted to do, and a complete list of all valid values makes it very easy to fix [TemplateDoesNotExist]{.title-ref} errors.

NoReverseMatch errors

Have you ever gotten this error?

django.urls.exceptions.NoReverseMatch: Reverse for 'view-name' with arguments '('',)' not found. 1 pattern(s) tried:

It\'s because you have {% url 'view-name' does_not_exist %}. Django sees does_not_exist and evaluates it to the empty string because it doesn\'t exist. So that\'s why you get an error message that makes no sense. django-fastdev will make your code crash on the actual error: does_not_exist doesn\'t exist.

Error if you have non-space text outside a block when extending

A common mistake for beginners that can be hard to spot is when they do:

<html>
    {% extends "something.html" %}
    stuff here
</html>

Django silently throws away stuff here and </html>. django-fastdev makes this an error.

Error on invalid block names when using `{% extends "..." %}`

If you have a base template:

<html>
    <body>
        {% block content %}{% endblock %}
    </body>
</html>

and then write a template like this:

{% extends "base.html" %}

{% block contents %}
    hello!
{% endblock %}

Django will silently throw away [hello!]{.title-ref} because you wrote contents instead of content. django-fastdev will turn this into an error which lists the invalid and valid block names in alphabetical order.

Better error messages for reverse

The standard error message for a bad reverse()/{% url %} are rather sparse. django-fastdev improves them by listing valid patterns so you can easily see the problem.

Better error messages for QuerySet.get()

The error message for QuerySet.get() is improved to give you the query parameters that resulted in the exception.

Validate clean* methods

A common mistake is to make a form clean method and make a spelling error. By default Django just won\'t call the function. With django-fastdev you will get an error message telling you that your clean method doesn\'t match anything.

This is also very useful during refactoring. Renaming a field is a lot safer as if you forget to rename the clean method django-fastdev will tell you!

By default, django-fastdev will check only forms that exist within your project, and not third-party libraries. If you would like to enable stricter validation that will extend to ALL forms, you can set this by configuring FASTDEV_STRICT_FORM_CHECKING to True in your Django settings.

Faster startup

The initial model checks can be quite slow on big projects. django-fastdev will move these checks to a separate thread, so the runserver startup time is lowered, so you don\'t have to wait for the runserver restart as long.

Usage

First install: pip install django-fastdev

In settings.py add django_fastdev to INSTALLED_APPS:

INSTALLED_APPS = [
    # ...
    'django_fastdev',
]

Enjoy a nicer Django experience!

License

BSD