django-querystring-tag 1.0

No project description provided

django-querystring-tag

This tiny package adds the {% querystring %} tag: A powerful, well tested template tag for modifying and rendering safe, suitably-encoded querystring values.

It's the clean and simple way to create pagination links, filters and other state-preserving links, without cluttering up your view code!

Installation

1. Install the package from pypi:

   With Poetry

   $ poetry add django-querystring-tag
   

   With pip

   $ pip install django-querystring-tag
   

2. Add "querystring_tag" to the INSTALLED_APPS list in your Django project settings.

3. Optional: To use the {% querystring %} tag freely, without having to {% load %} it into templates, add "querystring_tag.templatetags.querystring_tag" to the ['OPTIONS']['builtins'] list for your chosen template backend. See an example.

How to use

Load the tag in the templates where you want to use it, by adding the following to the template (usually at the top):

{% load querystring_tag %}

Modifying the data

Query data can be modified 'on-the-fly', using keyword arguments to specify what you'd like to change.

Replacing parameter value

The most common requirement is to completely replace the value for a specific parameter. This is done using a regular keyword argument, with an = operator between the parameter name and value. For example:

{% querystring foo="bar" %}

Removing a parameter value

When working with multi-value parameters, you may find yourself having to remove a specific value, without affecting any other values.

In these situations, you can use the -= operator instead of the usual =. For example, if the current querystring looked something like this:

?q=test&bar=1&bar=2&bar=3

And you wanted to remove &bar=2, your querystring tag might look like this:

{% querystring bar-=2 %}

If the specified value isn't present, the instruction will simply be ignored.

Adding to a parameter value

When working with multi-value parameters, you may find yourself having to add a specific value for a parameter, without affecting any other values.

In these situations, you can use the += operator instead of the usual =. For example, if the current querystring looked something like this:

?q=test&bar=1&bar=2&bar=3

And you wanted to add &bar=4, your querystring tag might look like this:

{% querystring bar+=4 %}```

If the specified value is already present, the instruction will simply be ignored.

Template variable support

Unlike a lot of custom template tags, {% querystring %} supports the use of template variables in keys as well as values. For example, if the tag was being used to generate pagination links, and page_param_name and page_num were variables available in the template, you could use them both like so:

{% querystring page_param_name=page_num %}

Supported value types

Values can be strings, booleans, integers, dates, datetimes, Django model instances, or iterables of either of these values.

When encountering a Django model instance, {% querystring %} will automatically take the pk value from it, and use that to modify the querystring. To use a different field value, you can use the tag's model_value_field option (see further down for details). Alternatively, you can add a querystring_value_field attribute to your model class. For example:

class Category(models.Model):
    name = models.CharField(max_length=50)
    slug = models.SlugField(max_length=50, unique=True)

    # use 'slug' values in querystrings
    querystring_value_field = "slug"

Specifying multiple values

As mentioned above, you can provide an iterable as a value to specify multiple values for a parameter at once. That could be a native Python type, such as a list, tuple or set, but could also be anything that implements the __iter__ method to support iteration, for example, a QuerySet.

For example, if the context contained a variable tag_list, which was list of strings (['tag1', 'tag2', 'tag3']), you can include all of those values by referencing the list value. For example:

{% querystring tags=tag_list %}

The output of the above would be:

"?tags=tag1&tags=tag2&tags=tag3"

Options reference

source_data

Supported value types: QueryDict, dict, str

Default value: request.GET

The tag defaults to using request.GET as the data source for the querystring, but the source_data keyword argument can be used to specify use an alternative QueryDict, dict or string value.

For example, say you were using a Django form to validate query data, and only want valid data to be included. You could use the Form's cleaned_data to generate a querystring instead:

{% load querystring_tag %}
{% querystring source_data=form.cleaned_data page=2 %}

remove_blank

Supported value types: bool

Default value: True

Any parameter values with a value of None or "" (an empty string) are removed from the querystring default.

To retain blank values, include remove_blank=False in your {% querystring %} tag.

remove_utm

Supported value types: bool

Default value: True

Parameter names starting with "utm_" (the format used for Google Analytics tracking parameters) are exluded from the generated querystrings by default, as it's unlikley that you'll want these to be repeated in links to other pages.

To retain these parameters instead, include remove_utm=False in your {% querystring %} tag.

model_value_field

Supported value types: str

Default value: "pk"

By default, when encountering a Django model instance as a value, {% querystring %} will take the pk value from the instance to use in the querystring. If you'd like to use a different field value, you can use the model_value_field option to specify an alternative field.

For example, if the model had a slug field that you were using as the public-facing identifier, you could specify that slug values be used in the querystring, like so:

{% querystring tags=tag_queryset model_field_value='slug' %}

only

Use this option at the start of your {% querystring %} tag when you only want the querystring to include values for specific parameters.

For example, say the current querystring looked like this:

?q=keywords&group=articles&category=2&published_after=2022-01-01

And you wanted to render a querystring containing only the q and group params. You could use only to achieve this:

{% load querystring_tag %}
{% querystring only 'q' 'group' %}

The resulting string would be:

?q=keywords&group=articles

NOTE: only is compatible with every other option except for discard. It can even be combined with any number of modifying keyword arguments; Just remember to keep the only keyword and related field names as the left-most parameters.

discard

Use this option at the start of your {% querystring %} tag when you want exclude specific parameter values from the querystring.

For example, say the current querystring looked like this:

?q=keywords&group=articles&category=2&published_after=2022-01-01

And you wanted to preserve everything except for group published_after in the rendered querystring. You could use discard to achieve this:

{% load querystring_tag %}
{% querystring discard 'group' 'published_after' %}

NOTE: discard is compatible with every other option except for only. It can even be combined with any number of modifying keyword arguments; Just remember to keep the discard keyword and related field names as the left-most parameters.

Testing the code locally

If you have a recent version of Python 3 installed, you can use a simple virtualenv to run tests locally. After cloning the repository, navigate to the project's root directory on your machine, then run the following:

To create the virtualenv

$ virtualenv venv
$ source venv/bin/activate
$ pip install -e '.[test]' -U
$ deactivate

To run tests

$ source venv/bin/activate
$ pytest
$ deactivate