Add subprocess handling to simplecov

CHANGELOG.md

@@ -1,3 +1,9 @@
+Unreleased
+==========
+
+## Enhancements
+* observe forked processes (enable with SimpleCov.enable_for_subprocesses)
+
 0.18.5 (2020-02-25)
 ===================
 

README.md

@@ -614,6 +614,53 @@ namespace :coverage do
 end
 ```
 
+## Running simplecov against subprocesses
+
+`SimpleCov.enable_for_subprocesses` will allow SimpleCov to observe subprocesses starting using `Process.fork`.
+This modifies ruby's core Process.fork method so that SimpleCov can see into it, appending `" (subprocess #{pid})"`
+to the `SimpleCov.command_name`, with results that can be merged together using SimpleCov's merging feature.
+
+To configure this, use `.at_fork`.
+
+```ruby
+SimpleCov.enable_for_subprocesses = true
+SimpleCov.at_fork do |pid|
+  # This needs a unique name so it won't be ovewritten
+  SimpleCov.command_name "#{SimpleCov.command_name} (subprocess: #{pid})"
+  # be quiet, the parent process will be in charge of output and checking coverage totals
+  SimpleCov.print_error_status = false
+  SimpleCov.formatter = SimpleCov::Formatter::SimpleFormatter
+  SimpleCov.minimum_coverage 0
+  # start
+  SimpleCov.start
+end
+```
+
+NOTE: SimpleCov must have already been started before `Process.fork` was called.
+
+### Running simplecov against spawned subprocesses
+
+Perhaps you're testing a ruby script with `PTY.spawn` or `Open3.popen`, or `Process.spawn` or etc.
+SimpleCov can cover this too.
+
+Add a .simplecov_spawn.rb file to your project root
+```ruby
+# .simplecov_spawn.rb
+require 'simplecov' # this will also pick up whatever config is in .simplecov
+                    # so ensure it just contains configuration, and doesn't call SimpleCov.start.
+SimpleCov.command_name 'spawn' # As this is not for a test runner directly, script doesn't have a pre-defined base command_name
+SimpleCov.at_fork.call(Process.pid) # Use the per-process setup described previously
+SimpleCov.start # only now can we start.
+```
+Then, instead of calling your script directly, like:
+```ruby
+PTY.spawn('my_script.rb') do # ...
+```
+Use bin/ruby to require the new .simplecov_spawn file, then your script
+```ruby
+PTY.spawn('ruby -r./.simplecov_spawn my_script.rb') do # ...
+```
+
 ## Running coverage only on demand
 
 The Ruby STDLIB Coverage library that SimpleCov builds upon is *very* fast (on a ~10 min Rails test suite, the speed

features/config_enable_for_subprocesses.feature

@@ -0,0 +1,37 @@
+@rspec
+
+Feature:
+  Coverage should include code run by subprocesses
+
+  Background:
+    Given I'm working on the project "subprocesses"
+
+  Scenario: Coverage has seen the subprocess line
+  When I open the coverage report generated with `bundle exec rspec spec/simple_spec.rb`
+  Then I should see the groups:
+    | name      | coverage | files |
+    | All Files | 100.0%   | 1     |
+
+  Scenario: The at_fork proc
+  Given a file named ".simplecov" with:
+    """
+    SimpleCov.enable_for_subprocesses = true
+    SimpleCov.command_name "parent process name"
+    SimpleCov.at_fork do |_pid|
+      SimpleCov.command_name "child process name"
+      SimpleCov.start
+    end
+    """
+  When I open the coverage report generated with `bundle exec rspec spec/simple_spec.rb`
+  Then I should see the groups:
+    | name      | coverage | files |
+    | All Files | 100.0%   | 1     |
+  And the report should be based upon:
+      | child process name  |
+      | parent process name |
+
+  Scenario: The documentation on .simplecov_spawn
+  When I open the coverage report generated with `bundle exec rspec spec/spawn_spec.rb`
+  Then I should see the groups:
+    | name      | coverage | files |
+    | All Files | 100.0%   | 1     |

lib/simplecov.rb

@@ -52,6 +52,8 @@ class << self
     def start(profile = nil, &block)
       require "coverage"
       initial_setup(profile, &block)
+      require_relative "./simplecov/process" if SimpleCov.enable_for_subprocesses
+
       @result = nil
       self.pid = Process.pid
 

lib/simplecov/configuration.rb

@@ -12,6 +12,7 @@ module SimpleCov
   #
   module Configuration # rubocop:disable Metrics/ModuleLength
     attr_writer :filters, :groups, :formatter, :print_error_status
+    attr_accessor :enable_for_subprocesses
 
     #
     # The root for the project. This defaults to the
@@ -196,6 +197,40 @@ def at_exit(&block)
       @at_exit ||= proc { SimpleCov.result.format! }
     end
 
+    #
+    # Gets or sets the behavior to start a new forked Process.
+    #
+    # By default, it will add " (Process #{pid})" to the command_name, and start SimpleCov in quiet mode
+    #
+    # Configure with:
+    #
+    #     SimpleCov.at_fork do |pid|
+    #       SimpleCov.start do
+    #         # This needs a unique name so it won't be ovewritten
+    #         SimpleCov.command_name "#{SimpleCov.command_name} (subprocess: #{pid})"
+    #         # be quiet, the parent process will be in charge of using the regular formatter and checking coverage totals
+    #         SimpleCov.print_error_status = false
+    #         SimpleCov.formatter = SimpleCov::Formatter::SimpleFormatter
+    #         SimpleCov.minimum_coverage 0
+    #         # start
+    #         SimpleCov.start
+    #       end
+    #     end
+    #
+    def at_fork(&block)
+      @at_fork = block if block_given?
+      @at_fork ||= lambda { |pid|
+        # This needs a unique name so it won't be ovewritten
+        SimpleCov.command_name "#{SimpleCov.command_name} (subprocess: #{pid})"
+        # be quiet, the parent process will be in charge of using the regular formatter and checking coverage totals
+        SimpleCov.print_error_status = false
+        SimpleCov.formatter = SimpleCov::Formatter::SimpleFormatter
+        SimpleCov.minimum_coverage 0
+        # start
+        SimpleCov.start
+      }
+    end
+
     #
     # Returns the project name - currently assuming the last dirname in
     # the SimpleCov.root is this.

lib/simplecov/process.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Process
+  class << self
+    def fork_with_simplecov(&block)
+      if defined?(SimpleCov) && SimpleCov.running
+        fork_without_simplecov do
+          SimpleCov.at_fork.call(Process.pid)
+          block.call if block_given?
+        end
+      else
+        fork_without_simplecov(&block)
+      end
+    end
+
+    alias fork_without_simplecov fork
+    alias fork fork_with_simplecov
+  end
+end

test_projects/subprocesses/.simplecov

@@ -0,0 +1,5 @@
+SimpleCov.enable_for_subprocesses = true
+# different versions of ruby were tracking different numbers of files. idk why.
+# lets only worry about one file.
+SimpleCov.add_filter /command/
+SimpleCov.add_filter /spawn/

test_projects/subprocesses/.simplecov_spawn.rb

@@ -0,0 +1,5 @@
+require 'bundler/setup'
+require 'simplecov'
+SimpleCov.command_name 'spawn'
+SimpleCov.at_fork.call(Process.pid)
+SimpleCov.start

test_projects/subprocesses/lib/command

@@ -0,0 +1,7 @@
+#!/usr/bin/env ruby
+
+require_relative './subprocesses'
+
+Subprocesses.new.run
+
+puts 'done'

test_projects/subprocesses/lib/subprocesses.rb

@@ -0,0 +1,21 @@
+class Subprocesses
+  def run
+    method_called_in_parent_process
+
+    pid = Process.fork do
+      method_called_by_subprocess
+    end
+
+    Process.wait(pid)
+
+    true
+  end
+
+  def method_called_in_parent_process
+    true
+  end
+
+  def method_called_by_subprocess
+    true
+  end
+end

test_projects/subprocesses/spec/simple_spec.rb

@@ -0,0 +1,7 @@
+require_relative "spec_helper"
+
+describe Subprocesses do
+  it "call things" do
+    expect(subject.run).to be true
+  end
+end

test_projects/subprocesses/spec/spawn_spec.rb

@@ -0,0 +1,10 @@
+require 'spec_helper'
+require 'open3'
+describe 'spawn' do
+  it 'calls things' do
+    Dir.chdir(File.expand_path('..', __dir__)) do
+      stdout, exitstatus = Open3.capture2("ruby -r./.simplecov_spawn lib/command")
+      expect(stdout.chomp).to eq 'done'
+    end
+  end
+end

test_projects/subprocesses/spec/spec_helper.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+require "simplecov"
+SimpleCov.start
+
+require_relative "../lib/subprocesses.rb"