Memoize recursive dependency checks; reduces calls to 'f.recursive_dependencies' by an order of magnitude

Library/Homebrew/cmd/uses.rb

@@ -54,11 +54,14 @@ module Homebrew
     end
     ignores << "recommended?" if ARGV.include? "--skip-recommended"
 
+    memo = {}
     uses = formulae.select do |f|
       used_formulae.all? do |ff|
         begin
           if recursive
             deps = f.recursive_dependencies do |dependent, dep|
+              memo_key = [dependent, dep].to_s
+              next if memo[memo_key]
               if dep.recommended?
                 Dependency.prune if ignores.include?("recommended?") || dependent.build.without?(dep)
               elsif dep.optional?
@@ -72,6 +75,7 @@ module Homebrew
               if dep.is_a?(TapDependency) && !dep.tap.installed?
                 Dependency.keep_but_prune_recursive_deps
               end
+              memo[memo_key] = true
             end
 
             dep_formulae = deps.flat_map do |dep|