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 (100-diagram visual regression suite)
• Themes — Default, Dark, Forest, Neutral

Usage

[dependencies]
ariel-rs = "0.4.0"

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

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

Supported diagram types

Type	Keyword(s)
Flowchart	flowchart / graph
Sequence	sequenceDiagram
Class	classDiagram / classDiagram-v2
State	stateDiagram / stateDiagram-v2
Entity Relationship	erDiagram
Gantt	gantt
Git	gitGraph
Pie	pie
Mindmap	mindmap
Timeline	timeline
Quadrant	quadrantChart
XY Chart	xychart-beta / xychart
C4	C4Context / C4Container / C4Component / C4Dynamic / C4Deployment
Block	block-beta / block
Packet	packet-beta / packet
Journey	journey
Requirement	requirementDiagram / requirement
Kanban	kanban
Sankey	sankey-beta / sankey
Treemap	treemap-beta / treemap
Radar	radar-beta / radar
Venn	venn-beta / vennDiagram / venn
Architecture	architecture-beta / architecture
Event Modeling	eventmodeling / event-modeling
Info	info
Ishikawa	fishbone / ishikawa
Wardley	wardley
TreeView	treeView-beta / treeView

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 for all themes
node run_regression_all.mjs                   # PNG conversion + compare + HTML report

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

Crate	Purpose
dagre-dgl-rs	Directed graph layout
ab_glyph	Font metrics for text measurement
indexmap	Deterministic map iteration
serde_json	JSON parsing (corpus loader)
chrono	Date handling for gantt diagrams

License

MIT © 2026 Rochanglien Infimate