build-graph

name	build-graph
description	Build cargo dependency graphs from Cargo.toml/Cargo.lock using the `graph` binary. Use when the user asks to analyze, scan, or build a dependency graph for a Rust/Cargo project. Triggers on: "build graph", "scan deps", "analyze dependencies", "dependency graph", "cargo graph", "graph build".

Build Graph

Build dependency graphs for Cargo projects using the graph binary.

Prerequisites

• graph binary built from the workspace: cargo build --bin graph
• Target project directory with Cargo.toml + Cargo.lock

Usage

./target/debug/graph build -w <project-dir> -o <output-dir> [--include-dev] [--include-build]

The binary uses a pure-Rust Cargo.lock parser (falls back automatically when cargo metadata is unavailable). No shell commands, no find, no Python.

Fallback Behavior

1. Primary: cargo_metadata::MetadataCommand — works when cargo is in PATH
2. Fallback: analyze_from_lockfile() — pure-Rust toml_edit parser, works in Nix sandbox, containers, minimal PATH environments

Output

<output-dir>/
├── graph.json     # GlobalDependencyGraph (JSON)
├── summary.txt    # Human-readable summary
└── analysis.json  # Metrics (nodes, edges, SCC count, density)

Graph JSON Format

{
  "nodes": [
    {
      "id": "crate:serde:1.0.203",
      "crate_name": "serde",
      "version": "1.0.203",
      "source": "registry+https://github.com/rust-lang/crates.io-index",
      "is_workspace_member": false,
      "edge_count": 0
    }
  ],
  "edges": [
    { "from": "crate:foo:0.1.0", "to": "crate:bar:0.2.0", "edge_type": "dependency" }
  ],
  "scc_count": 0,
  "total_scc_nodes": 0,
  "merged_projects": [],
  "statistics": { "total_nodes": 323, "total_edges": 705 }
}

Integration

• Batch scanning: for d in projects/*/; do graph build -w "$d" -o "graphs/$(basename $d)"; done
• Makefile target: make projects-graphs (uses PROJECTS_DIR=/home/mdupont/projects)
• Nix: nix build --impure .#graph-<project-name>

Examples

# Single project
./target/debug/graph build -w /home/mdupont/projects/pastebin -o /tmp/pastebin_graph

# Self-analysis
./target/debug/graph build -w . -o analysis/self_graph --include-dev --include-build

# Nix sandbox (no cargo binary available)
nix build --impure .#graph-pastebin

Troubleshooting

• "No Cargo.lock found": Run cargo generate-lockfile first
• "cargo metadata failed": Falls back automatically to lockfile parser
• "Only 1 node": Check that Cargo.toml is valid and Cargo.lock exists
• Slow discovery: Run from within the workspace root (not parent dir with 1000 subdirs)