Gitlab::Git::Popen can lazily hand output to a block

This allows input to start processing immediately without waiting for the process to complete.
This also allows long or infinite inputs to be partially processed,
which will termiate the process when reading stops with SIGPIPE.

1 files changed, 17 insertions, 0 deletions

diff --git a/spec/lib/gitlab/git/popen_spec.rb b/spec/lib/gitlab/git/popen_spec.rb
index 2b65bc1cf15..b033ede9062 100644
--- a/spec/lib/gitlab/git/popen_spec.rb
+++ b/spec/lib/gitlab/git/popen_spec.rb
@@ -53,6 +53,23 @@ describe 'Gitlab::Git::Popen' do
       it { expect(status).to be_zero }
       it { expect(output).to eq('hello') }
     end
+
+    context 'with lazy block' do
+      it 'yields a lazy io' do
+        expect_lazy_io = lambda do |io|
+          expect(io).to be_a Enumerator::Lazy
+          expect(io.inspect).to include('#<IO:fd')
+        end
+
+        klass.new.popen(%w[ls], path, lazy_block: expect_lazy_io)
+      end
+
+      it "doesn't wait for process exit" do
+        Timeout.timeout(2) do
+          klass.new.popen(%w[yes], path, lazy_block: ->(io) {})
+        end
+      end
+    end
   end
 
   context 'popen_with_timeout' do