Add a size method to the Queue class

packages/workbox-background-sync/Queue.mjs

@@ -162,6 +162,15 @@ class Queue {
     return this._removeRequest('shift');
   }
 
+  /**
+   * Returns the number of entries in the store.
+   *
+   * @return {number}
+   */
+  async size() {
+    return await this._queueStore.size();
+  }
+
   /**
    * Adds the entry to the QueueStore and registers for a sync event.
    *

packages/workbox-background-sync/lib/QueueStore.mjs

@@ -129,6 +129,22 @@ export class QueueStore {
     return this._removeEntry({direction: 'next'});
   }
 
+  /**
+   * Returns the number of entries in the store.
+   *
+   * @return {number}
+   * @private
+   */
+  async size() {
+    const cb = (txn, done) => {
+      txn.objectStore(OBJECT_STORE_NAME)
+          .index(INDEXED_PROP)
+          .count(IDBKeyRange.only(this._queueName))
+          .onsuccess = ({target}) => done(target.result);
+    };
+    return await this._db.transaction([OBJECT_STORE_NAME], 'readonly', cb);
+  }
+
   /**
    * Removes and returns the first or last entry in the queue (based on the
    * `direction` argument) matching the `queueName`.

packages/workbox-expiration/Plugin.mjs

@@ -31,7 +31,6 @@ import './_version.mjs';
  * used immediately.
  *
  * When using `maxEntries`, the entry least-recently requested will be removed from the cache first.
- * 
  *
  * @memberof workbox.expiration
  */

test/workbox-background-sync/sw/lib/test-QueueStore.mjs

@@ -528,4 +528,35 @@ describe(`QueueStore`, function() {
       expect(entries[2].id).to.equal(firstId + 2);
     });
   });
+
+  describe(`size`, function() {
+    it(`should return the number of entries in the store`, async function() {
+      const queueStore1 = new QueueStore('a');
+      const queueStore2 = new QueueStore('b');
+
+      const sr1 = await StorableRequest.fromRequest(new Request('/one'));
+      const sr2 = await StorableRequest.fromRequest(new Request('/two'));
+      const sr3 = await StorableRequest.fromRequest(new Request('/three'));
+      const sr4 = await StorableRequest.fromRequest(new Request('/four'));
+      const sr5 = await StorableRequest.fromRequest(new Request('/five'));
+
+      await queueStore1.pushEntry({requestData: sr1.toObject()});
+      await queueStore2.pushEntry({requestData: sr2.toObject()});
+
+      expect(await queueStore1.size()).to.equal(1);
+      expect(await queueStore2.size()).to.equal(1);
+
+      await queueStore2.pushEntry({requestData: sr3.toObject()});
+      await queueStore2.pushEntry({requestData: sr4.toObject()});
+      await queueStore1.pushEntry({requestData: sr5.toObject()});
+
+      expect(await queueStore1.size()).to.equal(2);
+      expect(await queueStore2.size()).to.equal(3);
+
+      await db.clear('requests');
+
+      expect(await queueStore1.size()).to.equal(0);
+      expect(await queueStore2.size()).to.equal(0);
+    });
+  });
 });

test/workbox-background-sync/sw/test-Queue.mjs

@@ -700,4 +700,15 @@ describe(`Queue`, function() {
       await queue.registerSync();
     });
   });
+
+  describe(`size`, function() {
+    it(`should return the size of the QueueStore instance`, async function() {
+      sandbox.stub(QueueStore.prototype, 'size').returns(10);
+
+      const queue = new Queue('a');
+      expect(await queue.size()).to.equal(10);
+
+      expect(QueueStore.prototype.size.callCount).to.equal(1);
+    });
+  });
 });