Prevent closure of primary window in Selenium driver

lib/capybara/selenium/driver.rb

@@ -26,6 +26,8 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
       @w3c = ((defined?(Selenium::WebDriver::Remote::W3CCapabilities) && @browser.capabilities.is_a?(Selenium::WebDriver::Remote::W3CCapabilities)) ||
               (defined?(Selenium::WebDriver::Remote::W3C::Capabilities) && @browser.capabilities.is_a?(Selenium::WebDriver::Remote::W3C::Capabilities)))
       main = Process.pid
+      @primary_window_handle = current_window_handle
+
       at_exit do
         # Store the exit status of the test run since it goes away after calling the at_exit proc...
         @exit_status = $ERROR_INFO.status if $ERROR_INFO.is_a?(SystemExit)
@@ -108,7 +110,8 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
     # Use instance variable directly so we avoid starting the browser just to reset the session
     return unless @browser
 
-    window_handles.reject { |handle| handle == current_window_handle }.each { |win| close_window(win) }
+    switch_to_window(@primary_window_handle)
+    window_handles.reject { |handle| handle == @primary_window_handle }.each { |win| close_window(win) }
 
     navigated = false
     start_time = Capybara::Helpers.monotonic_time
@@ -207,6 +210,7 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
   end
 
   def close_window(handle)
+    raise ArgumentError, "Not allowed to close the primary window" if handle == @primary_window_handle
     within_given_window(handle) do
       browser.close
     end

lib/capybara/spec/session/window/within_window_spec.rb

@@ -20,16 +20,15 @@ Capybara::SpecHelper.spec '#within_window', requires: [:windows] do
 
   context "with an instance of Capybara::Window" do
     it "should not invoke driver#switch_to_window when given current window" do
-      # switch_to_window is invoked in after hook
-      expect(@session.driver).to receive(:switch_to_window).exactly(3).times.and_call_original
+      allow(@session.driver).to receive(:switch_to_window).and_call_original
       @session.within_window @window do
         expect(@session.title).to eq('With Windows')
       end
+      expect(@session.driver).not_to have_received(:switch_to_window)
     end
 
     it "should be able to switch to another window" do
       window = (@session.windows - [@window]).first
-      expect(@session.driver).to receive(:switch_to_window).exactly(5).times.and_call_original
       @session.within_window window do
         expect(@session).to have_title(/Title of the first popup|Title of popup two/)
       end

spec/shared_selenium_session.rb

@@ -217,5 +217,13 @@ RSpec.shared_examples "Capybara::Session" do |session, mode|
         expect(@session).to have_current_path('/')
       end
     end
+
+    context "Windows" do
+      it "can't close the primary window" do
+        expect do
+          @session.current_window.close
+        end.to raise_error(ArgumentError, 'Not allowed to close the primary window')
+      end
+    end
   end
 end