Dagro

Dagro is a native Go port of Dagre, the directed graph layout engine. It intentionally replicates Dagre 0.8.5 and the Graphlib 2.1.8 behavior used by that release, including layout order, compound graphs, named multiedges, self-loops, and edge-label routing.

Dagro targets the exact Dagre 0.8.5 behavior embedded by D2. Later Dagre releases retain the same broad layout pipeline but include behavior-changing ordering, positioning, compound-layout, API, and dependency changes, so compatibility is measured against 0.8.5.

Usage

package main

import (
	"fmt"

	"github.com/d2lang/dagro"
)

func main() {
	g := dagro.NewGraph(dagro.GraphOptions{
		Compound:   true,
		Multigraph: true,
	}).SetGraph(dagro.Attrs{"rankdir": "TB"})

	g.SetDefaultEdgeLabel(func(string, string, *string) any {
		return dagro.Attrs{}
	})
	g.SetNode("a", dagro.Attrs{"width": 80, "height": 40})
	g.SetNode("b", dagro.Attrs{"width": 80, "height": 40})
	g.SetEdge("a", "b", dagro.Attrs{}, "a-to-b")

	if err := dagro.Layout(g); err != nil {
		panic(err)
	}

	a := g.Node("a").(dagro.Attrs)
	fmt.Println(a["x"], a["y"])
}

The API uses Attrs maps because Dagre and Graphlib labels are open JavaScript objects. Recognized numeric layout attributes accept Go numeric types and are coerced to float64 in the internal layout graph for JavaScript Number compatibility; arbitrary label values are preserved as supplied.

Compatibility and tests

The Go source follows the Dagre 0.8.5 module boundaries:

• cycle removal and greedy feedback-arc selection;
• compound nesting, normalization, and dummy-chain parenting;
• longest-path, tight-tree, and network-simplex ranking;
• weighted crossing minimization;
• Brandes-Köpf coordinate assignment;
• self-edge, label, border, direction, and translation passes.

The normal suite contains direct Go ports of the upstream tests. An optional differential suite replays ordered fixtures through both implementations and compares topology, point order, attribute presence, and all numeric output:

DAGRO_DAGRE_JS=/absolute/path/to/dagre-0.8.5.js go test ./...

The differential test uses node only as a test oracle. Dagro itself has no JavaScript runtime or third-party Go dependencies.

Versioning

Version reports the replicated Dagre version (0.8.5). Until the first tagged release, consumers developing Dagro and D2 together can use a Go workspace or a temporary local replace directive.

License

MIT. See LICENSE and NOTICE for upstream attribution and the exact compatibility revisions.