1 files changed, 138 insertions, 0 deletions
diff --git a/tools/profile b/tools/profile
new file mode 100755
index 0000000000..6fb571f43b
--- /dev/null
+++ b/tools/profile
@@ -0,0 +1,138 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+# Profile require calls giving information about the time and the files that are called
+# when loading the provided file.
+#
+# Example:
+#   tools/profile activesupport/lib/active_support.rb [ruby-prof mode] [ruby-prof printer]
+ENV["NO_RELOAD"] ||= "1"
+ENV["RAILS_ENV"] ||= "development"
+
+module CodeTools
+  class Profiler
+    Error = Class.new(StandardError)
+
+    attr_reader :path, :mode
+    def initialize(path, mode = nil)
+      assert_ruby_file_exists(path)
+      @path, @mode = path, mode
+      require "benchmark"
+    end
+
+    def profile_requires
+      GC.start
+      before_rss = `ps -o rss= -p #{Process.pid}`.to_i
+
+      if mode
+        require "ruby-prof"
+        RubyProf.measure_mode = RubyProf.const_get(mode.upcase)
+        RubyProf.start
+      else
+        Object.instance_eval { include RequireProfiler }
+      end
+
+      elapsed = Benchmark.realtime { require path }
+      results = RubyProf.stop if mode
+
+      GC.start
+      after_rss = `ps -o rss= -p #{Process.pid}`.to_i
+
+      if mode
+        if printer = ARGV.shift
+          puts "RubyProf outputting to stderr with printer #{printer}"
+          RubyProf.const_get("#{printer.to_s.classify}Printer").new(results).print($stdout)
+        elsif RubyProf.const_defined?(:CallStackPrinter)
+          filename = "#{File.basename(path, '.rb')}.#{mode}.html"
+          puts "RubyProf outputting to #{filename}"
+          File.open(filename, "w") do |out|
+            RubyProf::CallStackPrinter.new(results).print(out)
+          end
+        else
+          filename = "#{File.basename(path, '.rb')}.#{mode}.callgrind"
+          puts "RubyProf outputting to #{filename}"
+          File.open(filename, "w") do |out|
+            RubyProf::CallTreePrinter.new(results).print(out)
+          end
+        end
+      end
+
+      RequireProfiler.stats.each do |file, depth, sec|
+        if sec
+          puts "%8.1f ms  %s%s" % [sec * 1000, " " * depth, file]
+        else
+          puts "#{' ' * (13 + depth)}#{file}"
+        end
+      end
+      puts "%8.1f ms  %d KB RSS" % [elapsed * 1000, after_rss - before_rss]
+    end
+
+    private
+
+      def assert_ruby_file_exists(path)
+        fail Error.new("No such file") unless File.exist?(path)
+        fail Error.new("#{path} is a directory") if File.directory?(path)
+        ruby_extension = File.extname(path) == ".rb"
+        ruby_executable = File.open(path, "rb") { |f| f.readline } =~ [/\A#!.*ruby/]
+        fail Error.new("Not a ruby file") unless ruby_extension || ruby_executable
+      end
+
+      module RequireProfiler
+        private
+          def require(file, *args) RequireProfiler.profile(file) { super } end
+          def load(file, *args) RequireProfiler.profile(file) { super } end
+
+          @depth, @stats = 0, []
+          class << self
+            attr_accessor :depth
+            attr_accessor :stats
+
+            def profile(file)
+              stats << [file, depth]
+              self.depth += 1
+              result = nil
+              elapsed = Benchmark.realtime { result = yield }
+              self.depth -= 1
+              stats.pop if stats.last.first == file
+              stats << [file, depth, elapsed] if result
+              result
+            end
+          end
+      end
+  end
+end
+# ruby-prof printer name causes the third arg to be sent :classify
+#   which is probably overkill if you already know the name of the ruby-prof
+#   printer you want to use, e.g. Graph
+begin
+  require "active_support/inflector"
+  require "active_support/core_ext/string/inflections"
+rescue LoadError
+  STDERR.puts $!.message
+  class String
+    # File activesupport/lib/active_support/inflector/methods.rb, line 150
+    def classify
+      # strip out any leading schema name
+      camelize(sub(/.*\./, ""))
+    end
+    # File activesupport/lib/active_support/inflector/methods.rb, line 68
+    def camelize(uppercase_first_letter = true)
+      string = self
+      if uppercase_first_letter
+        string = string.sub(/^[a-z\d]*/) { |match| match.capitalize }
+      else
+        string = string.sub(/^(?:(?=\b|[A-Z_])|\w)/) { |match| match.downcase }
+      end
+      string.gsub(/(?:_|(\/))([a-z\d]*)/) { "#{$1}#{$2.capitalize}" }.gsub("/", "::")
+    end
+  end
+end
+if $0 == __FILE__
+  if (filename = ARGV.shift)
+    path = File.expand_path(filename)
+    mode = ARGV.shift
+    CodeTools::Profiler.new(path, mode).profile_requires
+  else
+    STDERR.puts "No file path entered. Usage is tools/profile path/to/file.rb [ruby-prof mode] [ruby-prof printer]"
+  end
+end