#graphviz.mbt

graphviz.mbt is a MoonBit rewrite of Graphviz focused on strict output parity for the dot pipeline.

The repository currently targets byte-for-byte compatibility with upstream Graphviz 14.1.1 fixtures for:

dot
xdot
svg

This project is built as a multi-package MoonBit module and includes a native dot-style CLI, a DOT parser/writer, layout code, and renderers.

#Status

The project is under active development. The main engineering goal is not just "similar rendering", but reproducible Graphviz-compatible behavior backed by strict fixtures and regression guards.

Today the repository includes:

a native CLI frontend at src/cmd/dot
DOT parsing and writing
DOT layout implementation in MoonBit
XDOT and SVG renderers
strict parity tests against upstream Graphviz reference outputs

The top-level parity contract is intentionally narrow: fixture expectations are authored from upstream Graphviz 14.1.1, not from this repository's own binary.

#Requirements

MoonBit with the moon CLI
a native toolchain supported by moon --target native
Python 3 for some repository scripts
upstream Graphviz 14.1.1 when refreshing parity fixtures

For fixture authoring and refreshes, use an external Graphviz 14.1.1 binary such as:

/opt/homebrew/opt/graphviz@14.1.1/bin/dot
/usr/local/opt/graphviz@14.1.1/bin/dot

Do not generate parity fixtures with this repository's own dot.exe.

#Quick Start

Build the native CLI:

moon build src/cmd/dot --target native

Run it on a DOT file:

_build/native/debug/build/cmd/dot/dot.exe -Tsvg input.gv -o output.svg

Write layout-annotated DOT to stdout:

_build/native/debug/build/cmd/dot/dot.exe -Tdot input.gv

List currently supported output formats:

_build/native/debug/build/cmd/dot/dot.exe -T

Current CLI coverage includes:

output formats: dot, xdot, svg
frontend behavior compatible with dot and neato program names
common flags: -T, -K, -o, -G, -N, -E, -s, -n, -x, -v, -V

#Development

Basic local validation:

moon check --target native --deny-warn
moon test --target native --release --deny-warn

Before pushing a no-regression milestone, run the full local guard:

scripts/run_local_guard.sh

That guard covers:

the full release MoonBit test suite
strict parity checks for dot, xdot, and svg
fixture/case-list invariants
DOT_CAPTURE_ORDERING_INPUTS environment-invariance checks

For faster parity iteration on a small focus set:

scripts/check_strict_parity.py --formats dot xdot svg --focus ldbxtried typeshar

#Fixture Policy

Strict parity fixtures are reference artifacts, not self-generated expectations.

The fixture source of truth is upstream Graphviz 14.1.1.
Use an external Graphviz 14.1.1 binary to generate or refresh dot, xdot, and svg fixtures.
Treat refs/graphviz as source/input corpus and upstream code reference, not as the default fixture-authoring binary.
Do not use the repository's own dot.exe to define expected parity outputs.