stream: restore flow if there are 'data' handlers after once('readable')

Fixes: https://github.com/nodejs/node/issues/21398
See: https://github.com/nodejs/node/pull/21696

PR-URL: https://github.com/nodejs/node/pull/22209
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Mathias Buus <mathiasbuus@gmail.com>

1 files changed, 61 insertions, 0 deletions

diff --git a/test/parallel/test-stream-once-readable-pipe.js b/test/parallel/test-stream-once-readable-pipe.js
new file mode 100644
index 0000000000..e8f4e9422d
--- /dev/null
+++ b/test/parallel/test-stream-once-readable-pipe.js
@@ -0,0 +1,61 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const { Readable, Writable } = require('stream');
+
+// This test ensures that if have 'readable' listener
+// on Readable instance it will not disrupt the pipe.
+
+{
+  let receivedData = '';
+  const w = new Writable({
+    write: (chunk, env, callback) => {
+      receivedData += chunk;
+      callback();
+    },
+  });
+
+  const data = ['foo', 'bar', 'baz'];
+  const r = new Readable({
+    read: () => {},
+  });
+
+  r.once('readable', common.mustCall());
+
+  r.pipe(w);
+  r.push(data[0]);
+  r.push(data[1]);
+  r.push(data[2]);
+  r.push(null);
+
+  w.on('finish', common.mustCall(() => {
+    assert.strictEqual(receivedData, data.join(''));
+  }));
+}
+
+{
+  let receivedData = '';
+  const w = new Writable({
+    write: (chunk, env, callback) => {
+      receivedData += chunk;
+      callback();
+    },
+  });
+
+  const data = ['foo', 'bar', 'baz'];
+  const r = new Readable({
+    read: () => {},
+  });
+
+  r.pipe(w);
+  r.push(data[0]);
+  r.push(data[1]);
+  r.push(data[2]);
+  r.push(null);
+  r.once('readable', common.mustCall());
+
+  w.on('finish', common.mustCall(() => {
+    assert.strictEqual(receivedData, data.join(''));
+  }));
+}