[core] Avoid bisect command to get stuck (rspec/rspec-core#2669)

Avoid bisect command to get stuck

---
This commit was imported from rspec/rspec-core@1c31fc4.

rspec-core/lib/rspec/core/bisect/fork_runner.rb

@@ -91,8 +91,9 @@ def initialize(runner, channel)
           end
 
           def dispatch_specs(run_descriptor)
-            pid = fork { run_specs(run_descriptor) }
-            Process.waitpid(pid)
+            fork { run_specs(run_descriptor) }
+            # We don't use Process.waitpid here as it was causing bisects to
+            # block due to the file descriptor limit on OSX / Linux.
           end
 
         private

rspec-core/spec/integration/bisect_spec.rb

@@ -32,5 +32,15 @@ def bisect(cli_args, expected_status=nil)
         expect(output).to include("Bisect failed!", "The example ordering is inconsistent")
       end
     end
+
+    context "when the bisect commasaturingnd is long" do
+      # On OSX and Linux a file descriptor limit meant that the bisect process got stuck at a certain limit.
+      # This test demonstrates that we can run large bisects above this limit (found to be at time of commit).
+      # See: https://github.com/rspec/rspec-core/pull/2669
+      it 'does not hit pipe size limit and does not get stuck' do
+        output = bisect(%W[spec/rspec/core/resources/blocking_pipe_bisect_spec.rb_], 1)
+        expect(output).to include("No failures found.")
+      end
+    end
   end
 end

rspec-core/spec/rspec/core/resources/blocking_pipe_bisect_spec.rb_

@@ -0,0 +1,8 @@
+# Deliberately named *.rb_ to avoid being loaded except when specified
+
+RSpec.describe "1000 tests" do
+  puts "Try to saturate the pipe in Bisect command"
+  (0..1000).each do |t|
+    it { expect(t).to eq t }
+  end
+end