Graph of Homebrew's "require"

brew-graph-require.rb

# brew graph-require [--command=<command>] [--full|--start=<file>]

require "set"
require "pp"

# Handle arguments.
dump_command = ARGV.value("command")
dump_full = ARGV.include?("--full")
dump_start = ARGV.value("start") || "../brew"

# Find files to scan and link to.
base = HOMEBREW_LIBRARY_PATH.to_s
files = ["../brew"]
files += Dir["#{base}/**/*.rb"].map { |f| f[(base.length + 1)..-4] }
files.reject! { |f| f.start_with?("test/", "vendor/") }

# Scan selected files for
missing = Set.new
links = {}
files.each do |source|
  links[source] = Set.new
  lines = IO.readlines("#{base}/#{source}.rb").map(&:chomp)
  lines.grep(/^(\s*)require\s+(.*)$/) do |line|
    indent, arg = line.match(/^(\s*)require\s+(.*)$/)[1..2]
    if arg =~ /^"([^"]+)"(.*)$/
      target, tail = $1, $2

      $stderr.puts "#{source}: Bogus require: >#{target}<" if target.include?(".")
      next if target.start_with?("test/", "vendor/")
      if !files.include?(target)
        missing << target
        next
      end

      if indent.empty? && tail.empty?
        links[source] << [target, :required]
      else
        links[source] << [target, :conditional]
      end
    else
      $stderr.puts "#{source}: Skipped 'require' line: >#{line}<"
    end
  end
end
$stderr.puts "Missing/external: #{missing.sort.join(" ")}"

# Add non-discoverable links from `../brew` to (developer) commands.
if dump_command
  file = files.find { |f| f.end_with?("cmd/#{dump_command}") }
  links["../brew"] << [file, :conditional]
else
  files.select { |f| f.start_with?("cmd/", "dev-cmd/") }.each do |file|
    links["../brew"] << [file, :conditional]
  end
end

# Filter output.
if dump_full
  graph = links
else
  graph = {}
  queue = [dump_start]
  until queue.empty?
    source = queue.pop
    graph[source] = links[source]
    links[source].each { |f, _| queue << f unless graph.key?(f) }
  end
  $stderr.puts "Graph: #{graph.size}/#{links.size} nodes retained"
end

# Output graph.
node_index = 0
node_map = Hash.new { |h, k| h[k] = format("node_%04d", node_index += 1) }
puts "digraph G {"
puts "  rankdir=LR;"
graph.each do |node, edges|
  puts "  #{node_map[node]} [label=\"#{node}\"];"
  edges.each do |to_node, kind|
    edge_style = kind == :conditional ? " [style=dashed]" : ""
    puts "  #{node_map[node]} -> #{node_map[to_node]}#{edge_style};"
  end
end
puts "}"
#$stderr.puts graph.pretty_inspect