gracile

A polyglot templating engine with Svelte-inspired syntax. Write a template once — render it from Rust, the command line, or any JavaScript runtime with identical output. Not fast, but elegant.

Why?

Most template engines are tied to a single runtime. Jinja2 is Python. Tera is Rust. Handlebars has ports but no guarantees of identical behaviour. gracile is designed from the ground up to render identically across runtimes — embed it in a Rust binary, call it from the CLI, or import it in Node, Deno, Bun, or the browser. One template, every environment.

The syntax comes from Svelte — concise, expressive, and already familiar to anyone who has written a Svelte component.

What?

Hello, {= name}!

{#if items}
  {#each items as { label, count }}
    - {= label}: {= count | default("n/a")}
  {/each}
{:else}
  Nothing here yet.
{/if}

Expressions & control flow

• {= expr} — interpolation (HTML-escaped)
• {~ expr} — raw unescaped output
• {#if} {:else if} {:else} {/if} — conditionals
• {#each items as pat, idx} {:else} {/each} — loops with destructuring
• {#snippet name(params)} {/snippet} + {@render name(args)} — reusable fragments
• {#raw} {/raw} — verbatim passthrough
• {@const name = expr} — scoped bindings
• {@include "name"} — render a pre-registered template
• {! comment !} — stripped at render time

Expressions support ||, &&, ??, ? :, == != < > <= >=, in / not in, is / is not, + - * / %, !, . and [] access, array literals, and filter chains (value | filter | filter).

Filters — upper, lower, capitalize, trim, truncate, replace, split, sort, reverse, join, first, last, length, default, json, round, urlencode, escape

is tests — defined, undefined, none, odd, even, empty, truthy, falsy, string, number, iterable

Strict mode — errors on undefined variables instead of silently rendering empty strings.

How?

Rust

use gracile_core::{Engine, Value};
use std::collections::HashMap;

let mut ctx = HashMap::new();
ctx.insert("name".into(), Value::String("world".into()));

let output = Engine::new()
    .with_strict()
    .render("Hello, {= name}!", ctx)?;

CLI

gracile render template.html --data data.json

JavaScript / WASM

import { render } from '@gracile-rs/wasm';

const output = render('Hello, {= name}!', { name: 'world' });

Where?

Package	Description
gracile-core	Core Rust library
gracile-cli	Command-line interface
gracile-wasm	WebAssembly / npm package