django-render-static

django-render-static

Use Django's template engines to render static files that are collected during the collectstatic routine and likely served above Django at runtime. Files rendered by django-render-static are immediately available to participate in the normal static file collection pipeline.

For example, a frequently occurring pattern that violates the DRY principle is the presence of defines, or enum like structures in server side Python code that are simply replicated in client side JavaScript. Another example might be rebuilding Django URLs from arguments in a Single Page Application. Single-sourcing these structures by transpiling client side code from the server side code keeps the stack bone DRY.

django-render-static includes Python to Javascript transpilers for:

• Django's reverse function (urls_to_js)
• PEP 435 style Python enumerations (enums_to_js)
• Plain data define-like structures in Python classes and modules (defines_to_js)

Transpilation is extremely flexible and may be customized by using override blocks or extending the provided transpilers.

django-render-static also formalizes the concept of a package-time or deployment-time static file rendering step. It piggybacks off the existing templating engines and configurations and should therefore be familiar to Django developers. It supports both standard Django templating and Jinja templates and allows contexts to be specified in python, json or YAML.

You can report bugs and discuss features on the issues page.

Contributions are encouraged!

Full documentation at read the docs.

Installation

1. Clone django-render-static from GitHub or install a release off PyPI:

pip install django-render-static

1. Add 'render_static' to your INSTALLED_APPS :

INSTALLED_APPS = [
    'render_static',
]

1. Add a STATIC_TEMPLATES configuration directive to your settings file:

STATIC_TEMPLATES = {
    'templates' : [
        ('path/to/template':, {'context' {'variable': 'value'})
    ]
}

1. Run renderstatic preceding every run of collectstatic :

$> manage.py renderstatic
$> manage.py collectstatic

Usage

Transpiling Model Field Choices

You have an app with a model with a character field that has several valid choices defined in an enumeration type way, and you'd like to export those defines to JavaScript. You'd like to include a template for other's using your app to use to generate a defines.js file. Say your app structure looks like this::

.
└── examples
    ├── __init__.py
    ├── apps.py
    ├── defines.py
    ├── models.py
    ├── static_templates
    │   └── examples
    │       └── defines.js
    └── urls.py

Your defines/model classes might look like this:

class ExampleModel(Defines, models.Model):

    DEFINE1 = 'D1'
    DEFINE2 = 'D2'
    DEFINE3 = 'D3'
    DEFINES = (
        (DEFINE1, 'Define 1'),
        (DEFINE2, 'Define 2'),
        (DEFINE3, 'Define 3')
    )

    define_field = models.CharField(choices=DEFINES, max_length=2)

And your defines.js template might look like this:

{% defines_to_js modules="examples.models" %}

If someone wanted to use your defines template to generate a JavaScript version of your Python class their settings file might look like this:

STATIC_TEMPLATES = {
    'templates': [
        'examples/defines.js'
    ]
}

And then of course they would call renderstatic before collectstatic:

$> ./manage.py renderstatic
$> ./manage.py collectstatic

This would create the following file::

.
└── examples
    └── static
        └── examples
            └── defines.js

Which would look like this:

const defines = {
    ExampleModel: {
        DEFINE1: "D1",
        DEFINE2: "D2",
        DEFINE3: "D3",
        DEFINES: [["D1", "Define 1"], ["D2", "Define 2"], ["D3", "Define 3"]]
    }
};

Transpiling Enumerations

Say instead of the usual choices tuple you're using PEP 435 style python enumerations as model fields using django-enum and enum-properties. For example we might define a simple color enumeration like so:

from django.db import models
from django_enum import EnumField, TextChoices
from enum_properties import p, s

class ExampleModel(models.Model):

    class Color(TextChoices, s('rgb'), s('hex', case_fold=True)):

        # name   value   label       rgb       hex
        RED   =   'R',   'Red',   (1, 0, 0), 'ff0000'
        GREEN =   'G',   'Green', (0, 1, 0), '00ff00'
        BLUE  =   'B',   'Blue',  (0, 0, 1), '0000ff'

    color = EnumField(Color, null=True, default=None)

If we define an enum.js template that looks like this:

    {% enums_to_js enums="examples.models.ExampleModel.Color" %}

It will contain a javascript class transpilation of the Color enum that looks like this:

class Color {

    static RED = new Color("R", "RED", "Red", [1, 0, 0], "ff0000");
    static GREEN = new Color("G", "GREEN", "Green", [0, 1, 0], "00ff00");
    static BLUE = new Color("B", "BLUE", "Blue", [0, 0, 1], "0000ff");

    constructor (value, name, label, rgb, hex) {
        this.value = value;
        this.name = name;
        this.label = label;
        this.rgb = rgb;
        this.hex = hex;
    }

    toString() {
        return this.value;
    }

    static get(value) {
        switch(value) {
            case "R":
                return Color.RED;
            case "G":
                return Color.GREEN;
            case "B":
                return Color.BLUE;
        }
        throw new TypeError(`No Color enumeration maps to value ${value}`);
    }

    static [Symbol.iterator]() {
        return [Color.RED, Color.GREEN, Color.BLUE][Symbol.iterator]();
    }
}

We can now use our enumeration like so:

Color.BLUE === Color.get('B');
for (const color of Color) {
    console.log(color);
}

Transpiling URL reversal

You'd like to be able to call something like reverse on path names from your client JavaScript code the same way you do from Python Django code.

Your settings file might look like:

    STATIC_TEMPLATES={
        'ENGINES': [{
            'BACKEND': 'render_static.backends.StaticDjangoTemplates',
            'OPTIONS': {
                'loaders': [
                    ('render_static.loaders.StaticLocMemLoader', {
                        'urls.js': '{% urls_to_js %}'
                    })
                ]
            },
        }],
        'templates': ['urls.js']
    }

Then call renderstatic before collectstatic:

$> ./manage.py renderstatic
$> ./manage.py collectstatic

If your root urls.py looks like this:

from django.contrib import admin
from django.urls import path

from .views import MyView

urlpatterns = [
    path('admin/', admin.site.urls),
    path('simple', MyView.as_view(), name='simple'),
    path('simple/<int:arg1>', MyView.as_view(), name='simple'),
    path('different/<int:arg1>/<str:arg2>', MyView.as_view(), name='different'),
]

So you can now fetch paths like this, in a way that is roughly API-equivalent to Django's reverse function:

import { URLResolver } from '/static/urls.js';

const urls = new URLResolver();

// /different/143/emma
urls.reverse('different', {kwargs: {'arg1': 143, 'arg2': 'emma'}});

// reverse also supports query parameters
// /different/143/emma?intarg=0&listarg=A&listarg=B&listarg=C
urls.reverse(
    'different',
    {
        kwargs: {arg1: 143, arg2: 'emma'},
        query: {
            intarg: 0,
            listarg: ['A', 'B', 'C']
        }
    }
);

URLGenerationFailed Exceptions & Placeholders

If you encounter a URLGenerationFailed exception you most likely need to register a placeholder for the argument in question. A placeholder is just a string or object that can be coerced to a string that matches the regular expression for the argument:

from render_static.placeholders import register_variable_placeholder

app_name = 'year_app'
urlpatterns = [
    re_path(r'^fetch/(?P<year>\d{4})/$', YearView.as_view(), name='fetch_year')
]

register_variable_placeholder('year', 2000, app_name=app_name)

Users should typically use a path instead of re_path and register their own custom converters when needed. Placeholders can be directly registered on the converter (and are then conveniently available to users of your app!):

from django.urls.converters import register_converter

class YearConverter:
    regex = '[0-9]{4}'
    placeholder = 2000  # this attribute is used by `url_to_js` to reverse paths

    def to_python(self, value):
        return int(value)

    def to_url(self, value):
        return str(value)


register_converter(YearConverter, 'year')

urlpatterns = [
    path('fetch/<year:year>', YearView.as_view(), name='fetch_year')
]