stream: avoid destroying writable source

ronag · ronag · commit ad0098d0c66f · 2020-03-11T21:29:45.000+01:00
User 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. Fixes: 4d93e10#commitcomment-37751035 Backport-PR-URL: #32212
diff --git a/lib/internal/streams/pipeline.js b/lib/internal/streams/pipeline.js
@@ -57,6 +57,10 @@ 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);
     }
diff --git a/test/parallel/test-stream-pipeline.js b/test/parallel/test-stream-pipeline.js
@@ -1016,3 +1016,19 @@ 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);
+}

Original file line number	Diff line number	Diff line change
`@@ -57,6 +57,10 @@ function destroyer(stream, reading, writing, final, callback) {`
`57`	`57`	`return callback();`
`58`	`58`	`}`
`59`	`59`
	`60`	`+ if (!err && reading && !writing && stream.writable) {`
	`61`	`+ return callback();`
	`62`	`+ }`
	`63`	`+`
`60`	`64`	`if (err \|\| !final \|\| !stream.readable) {`
`61`	`65`	`destroyImpl.destroyer(stream, err);`
`62`	`66`	`}`