Merge pull request #5509 from Polymer/5250-dequeue-before-run

Additional debouncer fixes

lib/utils/debounce.js

@@ -35,8 +35,8 @@ export class Debouncer {
     this._callback = callback;
     this._timer = this._asyncModule.run(() => {
       this._timer = null;
-      this._callback();
       debouncerQueue.delete(this);
+      this._callback();
     });
   }
   /**
@@ -161,6 +161,5 @@ export const flushDebouncers = function() {
       });
     }
   });
-  debouncerQueue = new Set();
   return didFlush;
 };

test/unit/debounce.html

@@ -38,7 +38,7 @@
 
 suite('enqueueDebouncer & flush', function() {
 
-  // NOTE: This is a regression test; the bug it fixed only occured if the
+  // NOTE: This is a regression test; the bug it fixed only occurred if the
   // debouncer was flushed before any microtasks run, hence it should be
   // first in this file
   test('re-enqueue canceled debouncer', function() {
@@ -55,6 +55,16 @@
     assert.isTrue(cb.calledOnce);
   });
 
+  test('flushDebouncers from enqueued debouncer', function(done) {
+    const cb = sinon.spy(() => flush());
+    let db = Debouncer.debounce(null, microTask, cb);
+    enqueueDebouncer(db);
+    setTimeout(() => {
+      assert.isTrue(cb.calledOnce);
+      done();
+    });
+  });
+
   const testEnqueue = (shouldFlush, done) => {
     const actualOrder = [];
     const enqueue = (type, {db, cb} = {}) => {
@@ -89,6 +99,21 @@
     testEnqueue(true, done);
   });
 
+  test('reentrant flush', function() {
+    const cb2 = sinon.spy();
+    let db2;
+    const cb1 = sinon.spy(() => {
+      flush();
+      db2 = Debouncer.debounce(null, microTask, cb2);
+      enqueueDebouncer(db2);
+    });
+    const db1 = Debouncer.debounce(null, microTask, cb1);
+    enqueueDebouncer(db1);
+    flush();
+    assert.isTrue(cb1.calledOnce);
+    assert.isTrue(cb2.calledOnce);
+  });
+
 });
 
 suite('debounce', function() {