stream: allow empty string as source of pipeline

Fixes: https://github.com/nodejs/node/issues/38721

PR-URL: https://github.com/nodejs/node/pull/38723
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

lib/internal/streams/utils.js

@@ -20,7 +20,7 @@ function isStream(obj) {
 }
 
 function isIterable(obj, isAsync) {
-  if (!obj) return false;
+  if (obj == null) return false;
   if (isAsync === true) return typeof obj[SymbolAsyncIterator] === 'function';
   if (isAsync === false) return typeof obj[SymbolIterator] === 'function';
   return typeof obj[SymbolAsyncIterator] === 'function' ||

test/parallel/test-stream-pipeline-with-empty-string.js

@@ -0,0 +1,18 @@
+'use strict';
+
+const common = require('../common');
+const {
+  pipeline,
+  PassThrough
+} = require('stream');
+
+
+async function runTest() {
+  await pipeline(
+    '',
+    new PassThrough({ objectMode: true }),
+    common.mustCall(() => { })
+  );
+}
+
+runTest().then(common.mustCall(() => {}));