Khnum Templates

Khnum is an HTML template engine for pure Dart servers. It supports layouts, includes, components, loops, and HTML escaping by default. It uses no Flutter, code generation, or reflection and works with Shelf, Dart Frog, Serverpod, or dart:io.

{{-- views/dashboard.khnum.html --}}
@extends("layouts.app")

@section("title", title)

@section("content")
<h1>{{ heading }}</h1>

@if(user)
    <x-alert type="success">Welcome back, {{ user.name }}!</x-alert>
@else
    <p>Please log in.</p>
@endif

<ul>
@foreach(items as item)
    <li>{{ item.name }} {{ loop.last ? "" : "|" }}</li>
@endforeach
</ul>
@endsection

import 'package:khnum/khnum.dart';

final khnum = Khnum(
  viewsPath: 'views',
  environment: TemplateEnvironment.production,
);

final html = await khnum.render('dashboard', {
  'title': 'Dashboard',
  'heading': 'Hello',
  'user': user,        // Map, or any object with toJson()
  'items': items,
});

Return it from Shelf:

Response.ok(html, headers: {'content-type': 'text/html; charset=utf-8'});

A complete server is in example/shelf_example.dart (PORT=8080 dart run example/shelf_example.dart). The full guide, written in the style of the Laravel docs, is at docs/views.md.

Why not compile templates like Laravel Blade?

Laravel Blade turns .blade.php into PHP and lets PHP execute it. Dart has no eval, dart:mirrors does not exist in compiled binaries, and code generation would make every template edit a build step. Khnum instead uses a parsed AST and a small, safe expression language. Templates cannot run Dart; they read the data you pass and call the helpers you register.

What is supported

Area	Syntax
Escaped output	{{ expr }} (escapes & < > " '; null prints nothing)
Raw output	{!! expr !!}, HtmlString, {{ json(data) }} for <script>
Comments, literals	{{-- --}}, @{{ }}, @@
Conditionals	@if / @elseif / @else / @endif, @unless / @endunless
Loops	@foreach(items as item), @foreach(map as k => v), @for(i in items), loop.index/iteration/first/last/count/remaining/even/odd/depth/parent
Layouts	@extends, @section ... @endsection, @section("t", value), @yield("s", default), @parent, @show, @stop
Includes	@include("view"), @include("view", {"k": v}), shares the parent scope
Components	<x-name attr="s" :attr="expr" flag>, {{ slot }}, <x-slot name="s">, <x-slot:s>, @props({...}), {{ attributes }}, attributes.merge({...}), <x-forms.input> for subdirectories
Data	Map, List ([i], .length, .first, .last), objects via toJson(), or khnum.resolve<T>(...)
Expressions	literals, . and [], + - * / %, == != < <= > >=, && || !, ??, ?:, helper calls
Extensibility	helper(), directive(), resolve<T>(), share(), custom TemplateLoader
Modes	development (reload on file change) / production (parse once, in memory)
Errors	every exception carries the template name and line

Truthiness is Khnum-loose: null, false, 0, '' and empty collections are false.

Intentionally out of scope

@stack/@push, @once, @php, @verbatim, @forelse, @switch, @auth/@guest, @csrf/@method, @each, @lang, class-based components, method calls on data ({{ s.toUpperCase() }} is an error; use a helper), an on-disk compiled cache, streaming output, and any form of arbitrary Dart evaluation.

Security

• {{ }} escapes; only {!! !!}, HtmlString and custom directive output are raw.
• View names are validated before any filesystem access and must resolve under the views root, so ../ never works, in render, @include, @extends or components.
• Includes, components and layouts share a depth counter (maxDepth, default 64) so recursion throws instead of overflowing.
• Missing variables throw by default (MissingVariables.throwError) or evaluate to null (MissingVariables.treatAsNull).
• Templates are code. Never render templates uploaded by users: they cannot execute Dart, but they can read all of the data you pass and loop indefinitely.

Performance

benchmark/render_benchmark.dart renders a page made of a layout, a partial, two components and a 50-row table from the warm cache:

Mode	Per render	Throughput
dart run (JIT)	~115 µs	~8,600 renders/s
dart compile exe (AOT)	~125 µs	~8,000 renders/s

Measured on an Apple Silicon laptop with Dart 3.12; run it yourself for your hardware.

Running the checks

dart analyze
dart test
dart run benchmark/render_benchmark.dart
PORT=8080 dart run example/shelf_example.dart

License

MIT