cargo-tree-to-dot.py

import sys
import re

def parse_tree(lines):
    """
    Parse the cargo tree lines into a graph.
    Returns:
        nodes: set of node ids (name@version)
        edges: list of (parent, child) pairs
    """
    stack = []  # stack of (indent_level, node_id)
    nodes = set()
    edges = []

    # Regex to extract dependency: e.g. anyhow v1.0.98 or anyhow v1.0.98 (proc-macro)
    dep_re = re.compile(r"^\s*[├└]──\s+([^ ]+)\s+(v[\d\.]+)(?:\s+\(.+\))?")

    # First line is the root, special handling
    root_line = lines[0].strip()
    # Root might have path in parentheses, strip after space
    root_match = re.match(r"^([^ ]+)\s+(v[\d\.]+).*$", root_line)
    if root_match:
        root_name = root_match.group(1)
        root_version = root_match.group(2)
        root_id = f"{root_name}@{root_version}"
    else:
        raise ValueError("Could not parse root dependency line: " + root_line)

    nodes.add(root_id)
    stack.append( (0, root_id) )

    for line in lines[1:]:
        if not line.strip():
            continue

        # Count indent level: each indent is 4 spaces or a single vertical line + spaces
        # After the root line, each dependency line starts with some prefix like "│   " or "    "
        # Simplify by counting bytes before '├' or '└' (first occurrence)
        m = re.search(r"[├└]──", line)
        if not m:
            continue  # skip lines without dependency marker

        pos = m.start()
        # Indent level estimate: pos // 4 
        indent_level = pos // 4

        dep_match = dep_re.match(line)
        if not dep_match:
            # e.g. lines like [build-dependencies], skip
            continue

        name = dep_match.group(1)
        version = dep_match.group(2)
        node_id = f"{name}@{version}"
        nodes.add(node_id)

        # Find parent with indent_level-1
        # Pop from stack until top has indent_level < current
        while stack and stack[-1][0] >= indent_level:
            stack.pop()
        if stack:
            parent_id = stack[-1][1]
            edges.append( (parent_id, node_id) )
        else:
            # No parent found, treat as root's child
            edges.append( (root_id, node_id) )

        stack.append( (indent_level, node_id) 

        )

    return nodes, edges

def sanitize_label(label):
    # Escape quotes, backslashes for DOT labels
    return label.replace("\\", "\\\\").replace("\"", "\\\"")

def generate_dot(nodes, edges, graph_name="cargo_tree"):
    dot = []
    dot.append(f'digraph "{graph_name}" {{')
    dot.append('  rankdir=LR;')
    dot.append('  node [shape=box, style=filled, fillcolor="#EEEEEE"];')

    # Define nodes
    for node in nodes:
        # node is like pkg@version
        label = sanitize_label(node)
        dot.append(f'  "{node}" [label="{label}"];')

    # Define edges
    for parent, child in edges:
        # we invert the direction to make it more readable
        dot.append(f'  "{child}" -> "{parent}";')

    dot.append('}')
    return "\n".join(dot)

def main():
    if len(sys.argv) != 2:
        print("Usage: python cargo-tree-to-dot.py <cargo-tree-output-file>", file=sys.stderr)
        sys.exit(1)

    filename = sys.argv[1]
    with open(filename, "r", encoding="utf-8") as f:
        lines = f.readlines()

    nodes, edges = parse_tree(lines)
    dot_output = generate_dot(nodes, edges)
    print(dot_output)

if __name__ == "__main__":
    main()

Better alternative: https://github.com/jplatte/cargo-depgraph