ariel-rs

A faithful Rust port of Mermaid JS — renders diagrams to SVG without a browser, Node.js, or any JavaScript runtime.

Features

• 28 diagram types — all Mermaid built-ins
• Headless — pure Rust, no DOM, no JS runtime
• Fast — renders diagrams in microseconds
• Accurate — pixel-tested against Mermaid JS reference output (98-diagram visual regression suite)
• Themes — Default, Dark, Forest, Neutral

Usage

[dependencies]
ariel-rs = "0.2.0"

use ariel_rs::{render, theme::Theme};

let svg = render("flowchart TD\n    A --> B --> C", Theme::Default);
println!("{}", svg);

Supported diagram types

Error handling

If the input is invalid or the diagram type is unrecognised, render() returns a styled error SVG matching Mermaid's browser error format — it never panics.

Themes

use ariel_rs::{render, theme::Theme};

let svg = render(source, Theme::Dark);

Available themes: Theme::Default, Theme::Dark, Theme::Forest, Theme::Neutral.

Development

Run tests

cargo test

Run tests with coverage

cargo install cargo-tarpaulin
cargo tarpaulin --out Stdout

Visual regression

Requires Node.js.

cd visual-regression
npm install                                   # first time only
cargo run --bin render_corpus --release        # generate Rust SVGs
node svg_to_png.mjs rust                      # convert to PNG
node compare.mjs                              # compare vs reference

Architecture

ariel-rs uses dagre-dgl-rs for directed graph layout (flowcharts, class diagrams, state diagrams, ER diagrams) and implements all other diagram types from scratch.

Dependencies

License

MIT © 2026 Rochanglien Infimate