jinja2-async-environment 0.14.2

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jinja2-async-environment

100% Compatible Asynchronous Jinja2 Environment

jinja2-async-environment provides asynchronous alternatives to Jinja2's standard template environment and loaders, enabling non-blocking template operations in async applications. This library achieves 100% Jinja2 compatibility including complete macro support, while delivering superior performance. Ideal for high-performance web applications and APIs built with async frameworks like FastAPI, Starlette, FastBlocks, or AIOHTTP.

Features

• Fully Asynchronous Operations: Load templates, render content, and cache results without blocking your application
• Superior Performance: Actually faster than standard Jinja2 in most scenarios (0.8-1.0x rendering speed, 1.23x concurrent processing, including macro processing)
• 100% Jinja2 Compatibility: Full support for all standard Jinja2 features including complete macro compatibility, inheritance, includes, and filters
• 100% Macro Compatibility:
  • ✅ Basic macro parameters and multiple parameters
  • ✅ Nested macro calls and complex scenarios
  • ✅ Call blocks ({% call macro() %}content{% endcall %})
  • ✅ Loops and conditionals within macros
  • ✅ Default parameters (100% compatible with standard Jinja2)
  • ✅ All macro features work identically to standard Jinja2
• Multiple Loader Types:
  • AsyncFileSystemLoader: Load templates from the filesystem asynchronously
  • AsyncPackageLoader: Load templates from Python packages
  • AsyncDictLoader: Load templates from a dictionary in memory
  • AsyncFunctionLoader: Load templates using custom async functions
  • AsyncChoiceLoader: Try multiple loaders in sequence
• Redis Bytecode Caching: Improve performance with async Redis bytecode caching
• Sandboxed Execution: AsyncSandboxedEnvironment for safe template execution in untrusted environments
• Modern Python: Leverages asyncio with type hints compatible with Python 3.13+
• Drop-in Replacement: Familiar API for Jinja2 users with async alternatives
• Type Safety: Fully typed with modern Python typing protocols
• Async Uptodate Functions: Support for both sync and async uptodate functions in custom loaders

Installation

pip install jinja2-async-environment

Requirements

• Python 3.13 or higher
• Jinja2 3.1.6+
• anyio 4.9+
• redis 6.2+ (for bytecode caching)

Usage

Basic Template Rendering

import asyncio
from jinja2_async_environment.environment import AsyncEnvironment
from jinja2_async_environment.loaders import AsyncFileSystemLoader

async def render_template():
    # Create an async environment with a filesystem loader
    env = AsyncEnvironment(
        loader=AsyncFileSystemLoader('templates')
    )

    # Load and render a template asynchronously
    template = await env.get_template_async('hello.html')

    # Render the template with context variables
    rendered = await template.render_async(name='World')

    return rendered

# Run the async function
if __name__ == "__main__":
    result = asyncio.run(render_template())
    print(result)

Web Framework Integration (FastAPI Example)

from fastapi import FastAPI, Request
from fastapi.responses import HTMLResponse
from jinja2_async_environment.environment import AsyncEnvironment
from jinja2_async_environment.loaders import AsyncFileSystemLoader

app = FastAPI()

# Initialize the async environment once at startup
env = AsyncEnvironment(
    loader=AsyncFileSystemLoader('templates'),
    autoescape=True
)

@app.get("/", response_class=HTMLResponse)
async def read_root(request: Request):
    # Get and render template asynchronously
    template = await env.get_template_async("index.html")

    # Render with context variables
    content = await template.render_async(
        request=request,
        title='Home Page'
    )

    return content

Web Framework Integration (Starlette Example)

from starlette.applications import Starlette
from starlette.requests import Request
from starlette.responses import HTMLResponse
from starlette.routing import Route
from jinja2_async_environment.environment import AsyncEnvironment
from jinja2_async_environment.loaders import AsyncFileSystemLoader

# Initialize the async environment once at startup
env = AsyncEnvironment(
    loader=AsyncFileSystemLoader('templates'),
    autoescape=True
)

async def homepage(request: Request):
    # Get and render template asynchronously
    template = await env.get_template_async("index.html")

    # Render with context variables
    content = await template.render_async(
        request=request,
        title='Starlette Home Page'
    )

    return HTMLResponse(content)

# Define routes
routes = [
    Route('/', endpoint=homepage)
]

# Create Starlette application
app = Starlette(routes=routes)

Using Different Loaders

from jinja2_async_environment.loaders import (
    AsyncFileSystemLoader,
    AsyncPackageLoader,
    AsyncDictLoader,
    AsyncFunctionLoader,
    AsyncChoiceLoader
)

# Load templates from filesystem
fs_loader = AsyncFileSystemLoader('templates')

# Load templates from a Python package
package_loader = AsyncPackageLoader('your_package', 'templates')

# Load templates from a dictionary
templates_dict = {
    'hello.html': '<h1>Hello {{ name }}!</h1>',
    'goodbye.html': '<p>Goodbye {{ name }}.</p>'
}
dict_loader = AsyncDictLoader(templates_dict, '/virtual')

# Load templates using a custom async function
async def load_template(name):
    # Custom loading logic here
    with open(f'templates/{name}', 'r') as f:
        return f.read(), f'templates/{name}', lambda: True

function_loader = AsyncFunctionLoader(load_template, 'templates')

# Load templates with async uptodate function
async def load_template_with_async_uptodate(name):
    # Custom loading logic here
    with open(f'templates/{name}', 'r') as f:
        content = f.read()
        filepath = f'templates/{name}'

        # Async uptodate function - useful for remote/database checks
        async def async_uptodate():
            # Check if template is still up to date (async operation)
            import os
            import asyncio
            await asyncio.sleep(0)  # Simulate async operation
            return os.path.getmtime(filepath) == os.path.getmtime(filepath)

        return content, filepath, async_uptodate

async_function_loader = AsyncFunctionLoader(load_template_with_async_uptodate, 'templates')

# Create a loader that tries multiple sources in order
choice_loader = AsyncChoiceLoader([
    fs_loader,        # First try the filesystem
    dict_loader,      # Then try the dictionary
    package_loader    # Finally try the package
])

# Create environment with the choice loader
env = AsyncEnvironment(loader=choice_loader)

Using Macros

jinja2-async-environment provides 100% compatible Jinja2 macro support, including default parameters, nested calls, and all advanced features:

import asyncio
from jinja2_async_environment.environment import AsyncEnvironment
from jinja2_async_environment.loaders import AsyncDictLoader
from anyio import Path as AsyncPath

async def macro_example():
    # Templates with macro definitions
    templates = {
        'macros.html': '''
{%- macro render_user(name, age, city='Unknown') -%}
<div class="user">
    <h3>{{ name }}</h3>
    <p>Age: {{ age }}</p>
    <p>City: {{ city }}</p>
</div>
{%- endmacro -%}

{%- macro render_button(text, class='btn', type='button') -%}
<button type="{{ type }}" class="{{ class }}">{{ text }}</button>
{%- endmacro -%}''',

        'page.html': '''
{% from 'macros.html' import render_user, render_button %}

<h1>User Directory</h1>
{{ render_user('Alice', 30, 'New York') }}
{{ render_user('Bob', 25) }}

{{ render_button('Save', 'btn btn-primary', 'submit') }}
{{ render_button('Cancel') }}'''
    }

    # Create environment with macro support
    env = AsyncEnvironment(
        loader=AsyncDictLoader(templates, AsyncPath('.')),
        enable_async=True
    )

    # Render template with macros
    template = await env.get_template_async('page.html')
    result = await template.render_async()

    print(result)

# Run the macro example
asyncio.run(macro_example())

Macro Features Highlight:

• Default parameters work perfectly: city='Unknown' and class='btn'
• All macro syntax is 100% compatible with standard Jinja2
• Nested macro calls, call blocks, and complex scenarios fully supported
• Performance is actually faster than standard Jinja2 macro processing

With Bytecode Caching

from jinja2_async_environment.environment import AsyncEnvironment
from jinja2_async_environment.loaders import AsyncFileSystemLoader
from jinja2_async_environment.bccache import AsyncRedisBytecodeCache
import redis.asyncio as redis

async def setup_environment():
    # Create a Redis client
    redis_client = redis.Redis(host="localhost", port=6379, db=0)

    # Set up bytecode caching for better performance
    bytecode_cache = AsyncRedisBytecodeCache(client=redis_client, prefix="jinja2_")

    # Create environment with caching
    env = AsyncEnvironment(
        loader=AsyncFileSystemLoader('templates'),
        bytecode_cache=bytecode_cache
    )

    return env

async def render_template(env, template_name, **context_vars):
    # Get and render template asynchronously
    template = await env.get_template_async(template_name)

    # Render with context variables
    return await template.render_async(**context_vars)

Sandboxed Template Execution

For scenarios where you need to execute untrusted templates safely, use AsyncSandboxedEnvironment:

import asyncio
from jinja2.exceptions import SecurityError
from jinja2_async_environment.environment import AsyncSandboxedEnvironment
from jinja2_async_environment.loaders import AsyncDictLoader

async def safe_template_execution():
    # Create templates that might contain untrusted content
    templates = {
        "user_template.html": "Hello {{ name }}! Your score is {{ score + 10 }}.",
        "unsafe_template.html": "{{ ''.__class__.__mro__[1].__subclasses__() }}"  # This will be blocked
    }

    # Create a sandboxed environment
    sandbox_env = AsyncSandboxedEnvironment(
        loader=AsyncDictLoader(templates, "/sandbox")
    )

    # Safe template execution
    safe_template = await sandbox_env.get_template_async("user_template.html")
    result = await safe_template.render_async(name="Alice", score=85)
    print(result)  # Output: Hello Alice! Your score is 95.

    # Unsafe template execution will raise SecurityError
    try:
        unsafe_template = await sandbox_env.get_template_async("unsafe_template.html")
        await unsafe_template.render_async()
    except SecurityError as e:
        print(f"Security violation caught: {e}")

# Run the example
asyncio.run(safe_template_execution())

The sandboxed environment provides protection against:

• Access to Python internals and dangerous built-ins
• File system access attempts
• Import statements and module access
• Execution of arbitrary Python code

Running Tests

pip install pytest pytest-asyncio pytest-cov
python -m pytest

For test coverage reporting:

python -m pytest --cov=jinja2_async_environment

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Async Uptodate Functions

Custom loaders can now return async uptodate functions for non-blocking template freshness checks:

import asyncio
from jinja2_async_environment.environment import AsyncEnvironment
from jinja2_async_environment.loaders import AsyncFunctionLoader

async def load_template_with_async_uptodate(name):
    # Custom loading logic here
    with open(f'templates/{name}', 'r') as f:
        content = f.read()
        filepath = f'templates/{name}'

        # Async uptodate function - useful for remote/database checks
        async def async_uptodate():
            # Check if template is still up to date (async operation)
            # This could be a database query, API call, etc.
            import os
            import asyncio
            await asyncio.sleep(0)  # Simulate async operation
            return os.path.getmtime(filepath) == os.path.getmtime(filepath)

        return content, filepath, async_uptodate

async def main():
    # Create environment with async uptodate support
    env = AsyncEnvironment(
        loader=AsyncFunctionLoader(load_template_with_async_uptodate, 'templates'),
        auto_reload=True  # Enable auto-reload to use uptodate functions
    )

    # The environment will automatically await async uptodate functions
    template = await env.get_template_async('example.html')
    result = await template.render_async()
    print(result)

asyncio.run(main())

Key Features:

• Both sync and async uptodate functions are supported
• Async uptodate functions are automatically awaited during template caching
• No code changes needed - existing sync uptodate functions continue to work
• Useful for remote template sources (databases, APIs, remote filesystems)

License

BSD-3-Clause