From c374648abf6f06bec80494a972c7ddce31a5444b Mon Sep 17 00:00:00 2001
From: Robert Nagy <ronagy@icloud.com>
Date: Mon, 2 Mar 2020 12:44:42 +0100
Subject: [PATCH] stream: add comments to pipeline implementation

Fixes: https://github.com/nodejs/node/issues/32039
---
 lib/internal/streams/pipeline.js | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/internal/streams/pipeline.js b/lib/internal/streams/pipeline.js
index 8c6cbf7524ea53..dda8396645bdcc 100644
--- a/lib/internal/streams/pipeline.js
+++ b/lib/internal/streams/pipeline.js
@@ -188,6 +188,11 @@ function pipeline(...streams) {
           PassThrough = require('_stream_passthrough');
         }
 
+        // If the last argument to pipeline is not a stream
+        // we must create a proxy stream so that pipeline(...)
+        // always returns a stream which can be further
+        // composed through `.pipe(stream)`.
+
         const pt = new PassThrough();
         if (isPromise(ret)) {
           ret
@@ -222,6 +227,9 @@ function pipeline(...streams) {
     }
   }
 
+  // TODO(ronag): Consider returning a Duplex proxy if the first argument
+  // is a writable. Would improve composability.
+  // See, https://github.com/nodejs/node/issues/32020
   return ret;
 }