Simon Willison’s Weblog

27th August 2024 - Link Blog

MiniJinja: Learnings from Building a Template Engine in Rust (via) Armin Ronacher's MiniJinja is his re-implemenation of the Python Jinja2 (originally built by Armin) templating language in Rust.

It's nearly three years old now and, in Armin's words, "it's at almost feature parity with Jinja2 and quite enjoyable to use".

The WebAssembly compiled demo in the MiniJinja Playground is fun to try out. It includes the ability to output instructions, so you can see how this:

<ul>
  {%- for item in nav %}
    <li>{{ item.title }}</a>
  {%- endfor %}
</ul>

Becomes this:

0   EmitRaw "<ul>"
1   Lookup  "nav"
2   PushLoop    1
3   Iterate 11
4   StoreLocal  "item"
5   EmitRaw "\n <li>"
6   Lookup  "item"
7   GetAttr "title"
8   Emit    
9   EmitRaw "</a>"
10  Jump    3
11  PopFrame    
12  EmitRaw "\n</ul>"