Modify XCScheme and write it back to disk in post_install script

I'm writing a post_install script in my Podfile in order to enable gathering of code coverage reports from my framework when I run the unit tests in the example project. Here's what I've got:

post_install do |installer|
  pods_project = installer.pods_project
  shared_data_dir = Xcodeproj::XCScheme.shared_data_dir(pods_project.path)
  scheme_filename = "BonMot.xcscheme"
  scheme = Xcodeproj::XCScheme.new File.join(shared_data_dir, scheme_filename)
  test_action = scheme.test_action
  test_action.code_coverage_enabled = true
  scheme.test_action = test_action
  puts "now scheme is #{scheme}"
  scheme.save!
end

When I print out the scheme, I can confirm that code coverage gathering is enabled, and when I check the modification date of the file, it is updated to the current time, although that is easily explained by the fact that I'm running pod install. The code coverage option is not being written back to the BonMot.xcscheme file. Why not?

Solution

Looks like post_install is too early to work with schemes. CocoaPods installer calls write_pod_project method right after run_podfile_post_install_hooks during "Generating Pods project" step and there is recreate_user_schemes call inside. So your scheme is rewritten every time during installation process.

I do not like my solution very match but it works for me:

post_install do |installer|

  orig_share_development_pod_schemes = installer.method :share_development_pod_schemes
  installer.define_singleton_method :share_development_pod_schemes do
    orig_share_development_pod_schemes.call

    # do what you want with schemes
  end

end

UPDATE (CocoaPods 1.2.0 and newer)

Since solution is based on implementation details it became broken when CocoaPods 1.2.0 had been released. Keeping the same direction I may suggest new method to redefine:

post_install do |installer|

  orig_write_lockfiles = installer.method :write_lockfiles
  installer.define_singleton_method :write_lockfiles do
    # do what you want with schemes

    orig_write_lockfiles.call
  end

end

UPDATE (CocoaPods 1.10.0 and newer)

Finally, we've got a solution without need to rely on implementation with new post_integrate_hook API:

post_integrate do |installer|
  # do what you want with schemes
end