plantuml-rs

Rust/wasm port of PlantUML: renders diagrams to SVG in the browser with no backend. See docs/PLAN.md for the porting decisions, the fidelity target and the current per-type status.

cargo install plantuml-cli          # or: cargo run --release -p plantuml-cli -- diagram.puml
plantuml-cli diagram.puml > diagram.svg
plantuml-cli -o build a.puml b.puml # one SVG per input
plantuml-cli --check *.puml         # validate in CI, non-zero exit on failure
plantuml-cli --json diagram.puml    # type, canvas size and SVG as JSON

Pre-built binaries for Linux, macOS (x64/arm64) and Windows are attached to every GitHub release, with checksums.

The library is plantuml-core (cargo add plantuml-core); the wasm build is on npm as plantuml-rs (see JavaScript). The API is unstable until 1.0; see CHANGELOG.md for what a release contains and docs/RELEASING.md for how releases are cut (publishing to crates.io runs on pushed tags).

Status

All 390 in-scope fixtures meet the fidelity target (text overlap >= 0.95, relative element placement >= 0.90) when measured with the reference metrics mode, and every fixture renders. 11 fixtures are documented accepted differences (embedded-diagram scale, handwritten mode and residual layout deltas); none of them is a missing feature or a crash. Supported today: sequence, class (with object and description diagrams), state, activity (with swimlanes, notes, loops and break), packet, chart, gantt, timing, mindmap, WBS, salt, JSON/YAML/HCL, Chen EER, EBNF and the crash diagram. C4-PlantUML renders through the bundled stdlib. Four C4/EBNF fixtures still miss the layout target; accepted differences and open items are listed in the plan.

JavaScript

const { render } = require('plantuml-rs');       // Node; ESM import works too
const svg = render('@startuml\nAlice -> Bob: hello\n@enduml');

In the browser the ESM build needs one await init() before render; see the package README. It is the same plantuml-core, compiled to wasm: no Java, no Graphviz, no network.

Editors

The VS Code extension PlantUML (plantuml-rs) (Open VSX) previews .puml files and renders puml fences in the built-in Markdown preview locally through the wasm build: syntax highlighting, PlantUML: Export SVG, no Java, no Graphviz process and no network. Sources are in editors/vscode.

Performance

On the 472-file Vega corpus the library renders 1.7 ms per diagram against 2.6 ms for Java PlantUML in one JVM — about 34% ahead — with roughly 31 ms of one-time initialization per process. Method, caveats and what is left are in docs/PERFORMANCE.md.

License

MIT. Ported code derives from PlantUML under its MIT option; graphviz-pure is EPL-2.0.