Added: bin/ddtracerb with exec command.

Author: delner

bin/ddtracerb

@@ -0,0 +1,15 @@
+#!/usr/bin/env ruby
+require 'ddtrace/tasks/exec'
+require 'ddtrace/tasks/help'
+
+command = ARGV.shift
+
+case command
+when 'exec'
+  Datadog::Tasks::Exec.new(ARGV).run
+when 'help', '--help'
+  Datadog::Tasks::Help.new.run
+else
+  puts "Command '#{command}' is not valid for ddtrace."
+  Datadog::Tasks::Help.new.run
+end

ddtrace.gemspec

@@ -29,8 +29,7 @@ Gem::Specification.new do |spec|
   end
 
   spec.files         = `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
-  spec.bindir        = 'exe'
-  spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.executables   = ['ddtracerb']
   spec.require_paths = ['lib']
 
   if RUBY_VERSION >= '2.2.0'

lib/ddtrace/profiling/preload.rb

@@ -0,0 +1,2 @@
+require 'ddtrace/profiling/tasks/setup'
+Datadog::Profiling::Tasks::Setup.new.execute

lib/ddtrace/profiling/tasks/setup.rb

@@ -0,0 +1,11 @@
+module Datadog
+  module Profiling
+    module Tasks
+      class Setup
+        def execute
+          # TODO
+        end
+      end
+    end
+  end
+end

lib/ddtrace/tasks/exec.rb

@@ -0,0 +1,33 @@
+module Datadog
+  module Tasks
+    # Wraps command with Datadog tracing
+    class Exec
+      attr_reader :args
+
+      def initialize(args)
+        @args = args
+      end
+
+      def run
+        set_rubyopt!
+        Kernel.exec(*args)
+      end
+
+      def rubyopts
+        [
+          '-rddtrace/profiling/preload'
+        ]
+      end
+
+      private
+
+      def set_rubyopt!
+        if ENV.key?('RUBYOPT')
+          ENV['RUBYOPT'] += " #{rubyopts.join(' ')}"
+        else
+          ENV['RUBYOPT'] = rubyopts.join(' ')
+        end
+      end
+    end
+  end
+end

lib/ddtrace/tasks/help.rb

@@ -0,0 +1,14 @@
+module Datadog
+  module Tasks
+    # Prints help message for usage of `ddtrace`
+    class Help
+      def run
+        puts %(
+Usage: ddtrace [command] [arguments]
+  exec [command]: Executes command with tracing & profiling preloaded.
+  help:           Prints this help message.
+        )
+      end
+    end
+  end
+end

spec/ddtrace/tasks/exec_spec.rb

@@ -0,0 +1,63 @@
+require 'spec_helper'
+require 'ddtrace/tasks/exec'
+
+RSpec.describe Datadog::Tasks::Exec do
+  subject(:task) { described_class.new(args) }
+  let(:args) { ['ruby', '-e', '"RUBY_VERSION"'] }
+
+  describe '::new' do
+    it { is_expected.to have_attributes(args: args) }
+  end
+
+  describe '#run' do
+    subject(:run) { task.run }
+    let(:result) { double('result') }
+
+    around do |example|
+      # Make sure RUBYOPT is returned to its original state.
+      original_opts = ENV['RUBYOPT']
+      example.run
+      ENV['RUBYOPT'] = original_opts
+    end
+
+    before do
+      # Must stub the call out or test will prematurely terminate.
+      expect(Kernel).to receive(:exec)
+        .with(*args)
+        .and_return(result)
+    end
+
+    context 'when RUBOPT is not defined' do
+      it 'runs the task with preloads' do
+        is_expected.to be(result)
+
+        # Expect preloading to have been attached
+        task.rubyopts.each do |opt|
+          expect(ENV['RUBYOPT']).to include(opt)
+        end
+      end
+    end
+
+    context 'when RUBYOPT is defined' do
+      before { ENV['RUBYOPT'] = start_opts }
+      let(:start_opts) { 'start_opts' }
+
+      it 'runs the task with additional preloads' do
+        is_expected.to be(result)
+
+        # Expect original RUBYOPT to have been preserved
+        expect(ENV['RUBYOPT']).to include(start_opts)
+
+        # Expect preloading to have been attached
+        task.rubyopts.each do |opt|
+          expect(ENV['RUBYOPT']).to include(opt)
+        end
+      end
+    end
+  end
+
+  describe '#rubyopts' do
+    subject(:rubyopts) { task.rubyopts }
+    it { is_expected.to eq(['-rddtrace/profiling/preload']) }
+  end
+end

spec/ddtrace/tasks/help_spec.rb

@@ -0,0 +1,16 @@
+require 'spec_helper'
+require 'ddtrace/tasks/help'
+
+RSpec.describe Datadog::Tasks::Help do
+  subject(:task) { described_class.new }
+
+  describe '#run' do
+    it 'prints a help message to STDOUT' do
+      expect(STDOUT).to receive(:puts) do |message|
+        expect(message).to include('Usage: ddtrace')
+      end
+
+      task.run
+    end
+  end
+end