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.

Manual snapshot regeneration helpers include:

• bash scripts/generate_dot_snapshots.sh
• bash scripts/generate_xdot_snapshots.sh
• bash scripts/generate_svg_snapshots.sh
• bash scripts/generate_svg_renderer_snapshots.sh

Some layout assets are intentionally pre-generated to avoid expensive pre-build steps. See:

• src/layout/dot/README.md
• src/render/xdot/README.md
• src/render/svg/README.md

Repository Layout

Core packages:

• src/cgraph: graph data model
• src/dot: DOT parsing and writing
• src/layout/dot: DOT layout pipeline
• src/render/xdot: XDOT renderer
• src/render/svg: SVG renderer
• src/cli: CLI parsing and render pipeline orchestration
• src/cmd/dot: native executable entrypoint

Useful documentation:

• docs/parity_guard.md: strict parity workflow and history scan tools
• docs/graphviz/architecture.md: upstream Graphviz architecture notes
• docs/graphviz/cli-and-formats.md: CLI and I/O format reference
• src/layout/dot/DOT_LAYOUT_ALGORITHM.md: end-to-end DOT layout pipeline notes

License

This project is licensed under the Eclipse Public License 2.0. See LICENSE.