README.md

Askama

Askama implements a template rendering engine based on Jinja. It generates Rust code from your templates at compile time based on a user-defined struct to hold the template's context. See below for an example, or read the documentation.

"I use Askama for actix's TechEmpower benchmarks." -- Nikolay Kim, creator of actix-web

"Pretty exciting. I would love to use this already." -- Armin Ronacher, creator of Jinja

All feedback welcome. Feel free to file bugs, requests for documentation and any other feedback to the issue tracker or tweet me. Many thanks to David Tolnay for his support in improving Askama.

Askama was created by and is maintained by Dirkjan Ochtman. If you are in a position to support ongoing maintenance and further development or use it in a for-profit context, please consider supporting my open source work on Patreon.

Feature highlights

• Construct templates using a familiar, easy-to-use syntax
• Template code is compiled into your crate for optimal performance
• Benefit from the safety provided by Rust's type system
• Optional built-in support for Actix, Gotham, Iron and Rocket web frameworks
• Debugging features to assist you in template development
• Templates must be valid UTF-8 and produce UTF-8 when rendered
• Works on stable Rust

Supported in templates

• Template inheritance
• Loops, if/else statements and include support
• Macro support
• Variables (no mutability allowed)
• Some built-in filters, and the ability to use your own
• Whitespace suppressing with '-' markers
• Opt-out HTML escaping
• Syntax customization

Limitations

• A limited number of built-in filters have been implemented

How to get started

First, add the following to your crate's Cargo.toml:

# in section [dependencies]
askama = "0.8"

Now create a directory called templates in your crate root. In it, create a file called hello.html, containing the following:

Hello, {{ name }}!

In any Rust file inside your crate, add the following:

extern crate askama; // for the Template trait and custom derive macro

use askama::Template; // bring trait in scope

#[derive(Template)] // this will generate the code...
#[template(path = "hello.html")] // using the template in this path, relative
                                 // to the templates dir in the crate root
struct HelloTemplate<'a> { // the name of the struct can be anything
    name: &'a str, // the field name should match the variable name
                   // in your template
}
   
fn main() {
    let hello = HelloTemplate { name: "world" }; // instantiate your struct
    println!("{}", hello.render().unwrap()); // then render it.
}

You should now be able to compile and run this code.

Review the test cases for more examples.

Debugging and troubleshooting

You can view the parse tree for a template as well as the generated code by changing the template attribute item list for the template struct:

#[derive(Template)]
#[template(path = "hello.html", print = "all")]
struct HelloTemplate<'a> { ... }

The print key can take one of four values:

• none (the default value)
• ast (print the parse tree)
• code (print the generated code)
• all (print both parse tree and code)

The resulting output will be printed to stderr during the compilation process.

The parse tree looks like this for the example template:

[Lit("", "Hello,", " "), Expr(WS(false, false), Var("name")),
Lit("", "!", "\n")]

The generated code looks like this:

impl < 'a > ::askama::Template for HelloTemplate< 'a > {
    fn render_into(&self, writer: &mut ::std::fmt::Write) -> ::askama::Result<()> {
        write!(
            writer,
            "Hello, {expr0}!",
            expr0 = &::askama::MarkupDisplay::from(&self.name),
        )?;
        Ok(())
    }
    fn extension() -> Option<&'static str> {
        Some("html")
    }
}
impl < 'a > ::std::fmt::Display for HelloTemplate< 'a > {
    fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
        ::askama::Template::render_into(self, f).map_err(|_| ::std::fmt::Error {})
    }
}