stream: defer readable and flow when sync

PR-URL: https://github.com/nodejs/node/pull/18515
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/test/parallel/test-stream-readable-pause-and-resume.js b/test/parallel/test-stream-readable-pause-and-resume.js
new file mode 100644
index 0000000000..505327e247
--- /dev/null
+++ b/test/parallel/test-stream-readable-pause-and-resume.js
@@ -0,0 +1,40 @@
+'use strict';
+
+const { Readable } = require('stream');
+const common = require('../common');
+
+let ticks = 18;
+let expectedData = 19;
+
+const rs = new Readable({
+  objectMode: true,
+  read: () => {
+    if (ticks-- > 0)
+      return process.nextTick(() => rs.push({}));
+    rs.push({});
+    rs.push(null);
+  }
+});
+
+rs.on('end', common.mustCall());
+readAndPause();
+
+function readAndPause() {
+  // Does a on(data) -> pause -> wait -> resume -> on(data) ... loop.
+  // Expects on(data) to never fire if the stream is paused.
+  const ondata = common.mustCall((data) => {
+    rs.pause();
+
+    expectedData--;
+    if (expectedData <= 0)
+      return;
+
+    setImmediate(function() {
+      rs.removeListener('data', ondata);
+      readAndPause();
+      rs.resume();
+    });
+  }, 1); // only call ondata once
+
+  rs.on('data', ondata);
+}