Flask-Liquid 0.1.1

A Flask extension for rendering Liquid templates.

A Flask extension for Liquid. Render Liquid templates in your Flask applications.

• Installing

• Quick Start

• Factories and Blueprints

• Mixing Jinja and Liquid

• Auto Escape

• Flask Standard Context

• Context Processors

• Signals

• Contributing

Installing

Install and update using pip:

$ python -m pip install -U flask-liquid

Requires Python>=3.8.

Quick Start

Flask-Liquid provides render_template and render_template_string functions that behave much like the Flask equivalents of the same name. By default Flask-Liquid will look for templates in the templates folder. The same location Flask uses for Jinja templates.

# saved as app.py
from flask import Flask

from flask_liquid import Liquid
from flask_liquid import render_template

app = Flask(__name__)
liquid = Liquid(app)

@app.route("/hello/")
@app.route("/hello/<name>")
def index(name=None):
    return render_template("index.html", name=name)

Set the LIQUID_TEMPLATE_FOLDER configuration value to change the Liquid template folder independently of app.template_folder.

app = Flask(__name__)
app.config.update(
    LIQUID_TEMPLATE_FOLDER="/path/to/liquid/templates/",
)

liquid = Liquid(app)

Factories and Blueprints

When using the factory pattern, use liquid.init_app(app) instead. Any LIQUID_* configuration values stored on the app will override Liquid constructor arguments when init_app is called.

from flask import Flask
from flask_liquid import Liquid

from yourapp.blueprints import some_blueprint

liquid = Liquid()

def create_app(config=None):
    app = Flask(__name__)
    app.register_blueprint(some_blueprint.bp)

    liquid.init_app(app)

    return app

Mixing Jinja and Liquid

If you want to use Jinja and Liquid templates side by side, import Liquid render functions using an alias.

from flask import render_template
from flask_liquid import render_template as render_liquid_template

Auto Escape

Whereas Flask configures Jinja with auto escaping enabled by default, forcing you to explicitly mark strings of HTML (for example) or template blocks as safe, Liquid does the opposite. Liquid includes the escape and escape_once filters for escaping untrusted strings, but does not have a safe filter nor an auto escape feature.

To render markup from a Liquid snippet inside a Jinja template, mark the string returned by render_liquid_template as safe using Markup, then include it in the Jinja template context. That is assuming you trust values in the Liquid render context and/or have used the escape filter appropriately in your Liquid templates.

from flask import Flask
from flask import Markup
from flask import render_template

from flask_liquid import Liquid
from flask_liquid import render_template as render_liquid_template

app = Flask(__name__)
liquid = Liquid(app)

@app.route("/hello")
def hello():
    user_content = render_liquid_template("content.liquid")
    return render_template("page.html", content=Markup(user_content))

Flask Standard Context

Flask has some standard context variables that are included in each Jinja template context automatically. Flask-Liquid does not include these variables. If you need access to the Flask session or request, for example, you’ll need to manually map session or request properties to Liquid context keys.

from flask import Flask
from flask import request

from flask_liquid import Liquid
from flask_liquid import render_template

app = Flask(__name__)
liquid = Liquid(app)

@app.route("/hello/")
@app.route("/hello/<name>")
def index(name=None):
    return render_template("index.html", name=name, path=request.path)

Context Processors

When the LIQUID_FLASK_CONTEXT_PROCESSORS configuration value is set to True, Flask context processors will update Liquid template contexts too. Be aware that Python Liquid relies on the Mapping interface for resolving identifiers, using operators.getitem internally. So for values returned from context processors to be useful within Liquid templates, they must behave like a dictionary.

from flask import Flask
from flask import request

from flask_liquid import Liquid
from flask_liquid import render_template

app = Flask(__name__)
app.config.update(
    LIQUID_FLASK_CONTEXT_PROCESSORS=True,
)

liquid = Liquid(app)

@app.context_processor
def extra_context():
    return {"request_path": request.path}

@app.route("/hello/")
@app.route("/hello/<name>")
def index(name=None):
    return render_template("index.html", name=name)

Signals

By default, when signals are available, Flask-Liquid will send a before_render_template and template_rendered signal for each successful call to render_template and render_template_string.

You can disable these signals for Liquid templates by setting the LIQUID_FLASK_SIGNALS configuration value to False.

Contributing

• Install development dependencies with Pipenv

• Flask-Liquid fully embraces type hints and static type checking. I like to use the Pylance extension for Visual Studio Code, which includes Pyright for static type checking.

• Format code using black.

• Write tests using unittest.TestCase.

• Run tests with make test or python -m unittest.

• Check test coverage with make coverage and open htmlcov/index.html in your browser.