rust_dot

It can be embedded as a macro or parsed from a string or file.

let g1 = rust_dot! {
   graph {
       A -- B -- C; /* semicolon is optional */
       "B" -- D // quotes not needed here
   }
};
println!("{} {} \"{}\" {:?} {:?}", g1.strict, g1.directed, g1.name, g1.nodes, g1.edges);
// false false "" ["A", "B", "C", "D"] [(0, 1), (1, 2), (1, 3)]

let g2 = parse_string("digraph Didi { -1 -> 2 -> 3  2 -> 4.2 }");
println!("{} {} \"{}\" {:?} {:?}", g2.strict, g2.directed, g2.name, g2.nodes, g2.edges);
// false true "Didi" ["-1", "2", "3", "4.2"] [(0, 1), (1, 2), (1, 3)]

The return values can be fed to crates petgraph (or graph/graph_builder):

let mut petgraph = petgraph::graph::Graph::new();
let nodes: Vec<_> = rust_dot_graph.nodes
   .iter()
   .map(|node| petgraph
       .add_node(node))
   .collect();
for edge in rust_dot_graph.edges {
   petgraph
       .add_edge(nodes[edge.0], nodes[edge.1], ());
};