Architecture

Pipeline

Nunjucks	Runjucks
lex → parse → transform → compile to JS → new Function → run	lex → parse → tree-walk render in Rust

Template context from JavaScript is passed as a plain object and converted to a JSON-compatible representation for the engine.

flowchart LR
  JS["Node.js: renderString / Environment"]
  R["Rust engine: lex → parse → render"]
  JS -->|"template + context"| R
  R -->|"string"| JS

The npm package is a thin binding layer around that engine. If you work on the Rust code, browse the Rust API (rustdoc) on this site or open the repo layout described there.

Reference implementation

When comparing behavior, the Nunjucks source remains the reference for intent. Runjucks does not compile templates to JavaScript or eval them; it evaluates an AST with the same broad language goals.