stream: avoid destroying writable source

lib/internal/streams/pipeline.js

@@ -50,6 +50,10 @@ function destroyer(stream, reading, writing, final, callback) {
  return callback();
  }
 
+ if (!err && reading && !writing && stream.writable) {
+ return callback();
+ }
+
  if (err || !final || !stream.readable) {
  destroyImpl.destroyer(stream, err);
  }

test/parallel/test-stream-pipeline.js

@@ -1032,3 +1032,19 @@ const { promisify } = require('util');
  req.on('error', common.mustNotCall());
  });
 }
+
+{
+ // Might still want to be able to use the writable side
+ // of src. This is in the case where e.g. the Duplex input
+ // is not directly connected to its output. Such a case could
+ // happen when the Duplex is reading from a socket and then echos
+ // the data back on the same socket.
+ const src = new PassThrough();
+ assert.strictEqual(src.writable, true);
+ const dst = new PassThrough();
+ pipeline(src, dst, common.mustCall((err) => {
+ assert.strictEqual(src.writable, true);
+ assert.strictEqual(src.destroyed, false);
+ }));
+ src.push(null);
+}