Keep bookmark returned after auto-commit tx

Auto-commit transactions return bookmarks in Bolt V3. They were
previously unused. This PR makes driver extract such bookmarks and
expose them via Session#lastBookmark(). It then possible for explicit
and auto-commit transactions within the same session to be chained
with bookmarks.

Author: lutovich

src/v1/session.js

@@ -89,7 +89,7 @@ class Session {
   }
 
   _run(statement, parameters, statementRunner) {
-    const streamObserver = new StreamObserver();
+    const streamObserver = new SessionStreamObserver(this);
     const connectionHolder = this._connectionHolderWithMode(this._mode);
     if (!this._hasTx) {
       connectionHolder.initializeConnection();
@@ -209,7 +209,6 @@ class Session {
   /**
    * Update value of the last bookmark.
    * @param {Bookmark} newBookmark the new bookmark.
-   * @private
    */
   _updateBookmark(newBookmark) {
     if (newBookmark && !newBookmark.isEmpty()) {
@@ -247,6 +246,23 @@ class Session {
   }
 }
 
+/**
+ * @private
+ */
+class SessionStreamObserver extends StreamObserver {
+
+  constructor(session) {
+    super();
+    this._session = session;
+  }
+
+  onCompleted(meta) {
+    super.onCompleted(meta);
+    const bookmark = new Bookmark(meta.bookmark);
+    this._session._updateBookmark(bookmark);
+  }
+}
+
 function _createTransactionExecutor(config) {
   const maxRetryTimeMs = (config && config.maxTransactionRetryTime) ? config.maxTransactionRetryTime : null;
   return new TransactionExecutor(maxRetryTimeMs);

test/v1/bolt-v3.test.js

@@ -256,6 +256,117 @@ describe('Bolt V3 API', () => {
       expect(() => session.writeTransaction(tx => tx.run('RETURN 1'), {metadata: invalidValue})).toThrow());
   });
 
+  it('should use bookmarks for auto commit transactions', done => {
+    if (!databaseSupportsBoltV3()) {
+      done();
+      return;
+    }
+
+    const initialBookmark = session.lastBookmark();
+
+    session.run('CREATE ()').then(() => {
+      const bookmark1 = session.lastBookmark();
+      expect(bookmark1).not.toBeNull();
+      expect(bookmark1).toBeDefined();
+      expect(bookmark1).not.toEqual(initialBookmark);
+
+      session.run('CREATE ()').then(() => {
+        const bookmark2 = session.lastBookmark();
+        expect(bookmark2).not.toBeNull();
+        expect(bookmark2).toBeDefined();
+        expect(bookmark2).not.toEqual(initialBookmark);
+        expect(bookmark2).not.toEqual(bookmark1);
+
+        session.run('CREATE ()').then(() => {
+          const bookmark3 = session.lastBookmark();
+          expect(bookmark3).not.toBeNull();
+          expect(bookmark3).toBeDefined();
+          expect(bookmark3).not.toEqual(initialBookmark);
+          expect(bookmark3).not.toEqual(bookmark1);
+          expect(bookmark3).not.toEqual(bookmark2);
+
+          done();
+        });
+      });
+    });
+  });
+
+  it('should use bookmarks for auto commit and explicit transactions', done => {
+    if (!databaseSupportsBoltV3()) {
+      done();
+      return;
+    }
+
+    const initialBookmark = session.lastBookmark();
+
+    const tx1 = session.beginTransaction();
+    tx1.run('CREATE ()').then(() => {
+      tx1.commit().then(() => {
+        const bookmark1 = session.lastBookmark();
+        expect(bookmark1).not.toBeNull();
+        expect(bookmark1).toBeDefined();
+        expect(bookmark1).not.toEqual(initialBookmark);
+
+        session.run('CREATE ()').then(() => {
+          const bookmark2 = session.lastBookmark();
+          expect(bookmark2).not.toBeNull();
+          expect(bookmark2).toBeDefined();
+          expect(bookmark2).not.toEqual(initialBookmark);
+          expect(bookmark2).not.toEqual(bookmark1);
+
+          const tx2 = session.beginTransaction();
+          tx2.run('CREATE ()').then(() => {
+            tx2.commit().then(() => {
+              const bookmark3 = session.lastBookmark();
+              expect(bookmark3).not.toBeNull();
+              expect(bookmark3).toBeDefined();
+              expect(bookmark3).not.toEqual(initialBookmark);
+              expect(bookmark3).not.toEqual(bookmark1);
+              expect(bookmark3).not.toEqual(bookmark2);
+
+              done();
+            });
+          });
+        });
+      });
+    });
+  });
+
+  it('should use bookmarks for auto commit transactions and transaction functions', done => {
+    if (!databaseSupportsBoltV3()) {
+      done();
+      return;
+    }
+
+    const initialBookmark = session.lastBookmark();
+
+    session.writeTransaction(tx => tx.run('CREATE ()')).then(() => {
+      const bookmark1 = session.lastBookmark();
+      expect(bookmark1).not.toBeNull();
+      expect(bookmark1).toBeDefined();
+      expect(bookmark1).not.toEqual(initialBookmark);
+
+      session.run('CREATE ()').then(() => {
+        const bookmark2 = session.lastBookmark();
+        expect(bookmark2).not.toBeNull();
+        expect(bookmark2).toBeDefined();
+        expect(bookmark2).not.toEqual(initialBookmark);
+        expect(bookmark2).not.toEqual(bookmark1);
+
+        session.writeTransaction(tx => tx.run('CREATE ()')).then(() => {
+          const bookmark3 = session.lastBookmark();
+          expect(bookmark3).not.toBeNull();
+          expect(bookmark3).toBeDefined();
+          expect(bookmark3).not.toEqual(initialBookmark);
+          expect(bookmark3).not.toEqual(bookmark1);
+          expect(bookmark3).not.toEqual(bookmark2);
+
+          done();
+        });
+      });
+    });
+  });
+
   function testTransactionMetadataWithTransactionFunctions(read, done) {
     if (!databaseSupportsBoltV3()) {
       done();