gen-graph

gen-graph is pure graph query combinators for Nix. Queries take accessor functions as arguments — not node maps. The graph structure is supplied by the caller; gen-graph only answers questions about it.

The problem it owns: reachability, roots, phase ordering, SCC partitioning — the questions every graph-shaped problem eventually asks — without forcing the caller to first materialize the graph into a concrete data structure gen-graph controls. You keep your own representation; gen-graph just needs a way to ask it “what are this node’s edges.”

It depends on nothing but gen-prelude. That makes it one of the roster’s widest load-bearing libraries: gen-bind, gen-inspect, gen-memo, gen-scope, gen-settings, and gen-view all build on it directly, and gen-scope’s well-founded engine consumes gen-graph’s SCC partitioning rather than carrying a second one of its own.

Take it alone

{
  inputs.gen-graph.url = "github:sini/gen-graph";
  # gen-graph pulls in gen-prelude transitively — no nixpkgs input required.

  outputs = { gen-graph, ... }:
    let graph = gen-graph.lib;
    in { /* use graph.reachableFrom, graph.roots, graph.phaseOrder, etc. */ };
}

Without flakes, the standalone entry derives gen-prelude from the pinned flake.lock and takes no arguments:

let
  graph = import ./path/to/gen-graph { };
in
graph.reachableFrom { edges = id: deps.${id} or [ ]; } "start"