fix: don't consume first document when calling hasNext on cursor

NODE-2454

Author: mbroadst

lib/cursor.js

@@ -124,8 +124,6 @@ class Cursor extends CoreCursor {
       state: CursorState.INIT,
       // Promise library
       promiseLibrary,
-      // Current doc
-      currentDoc: null,
       // explicitlyIgnoreSession
       explicitlyIgnoreSession: !!options.explicitlyIgnoreSession
     };
@@ -197,20 +195,18 @@ class Cursor extends CoreCursor {
   hasNext(callback) {
     return maybePromise(callback, cb => {
       const cursor = this;
-      if (cursor.s.currentDoc) {
-        return cb(null, true);
-      }
-
       if (cursor.isNotified()) {
         return cb(null, false);
       }
 
-      nextObject(cursor, (err, doc) => {
+      cursor._next((err, doc) => {
         if (err) return cb(err);
-        if (cursor.s.state === Cursor.CLOSED || cursor.isDead()) return cb(null, false);
-        if (!doc) return cb(null, false);
+        if (doc == null || cursor.s.state === Cursor.CLOSED || cursor.isDead()) {
+          return cb(null, false);
+        }
 
-        cursor.s.currentDoc = doc;
+        cursor.s.state = CursorState.OPEN;
+        cursor.cursorState.cursorIndex--;
         cb(null, true);
       });
     });
@@ -225,17 +221,7 @@ class Cursor extends CoreCursor {
    */
   next(callback) {
     return maybePromise(callback, cb => {
-      const cursor = this;
-
-      // Return the currentDoc if someone called hasNext first
-      if (cursor.s.currentDoc) {
-        const doc = cursor.s.currentDoc;
-        cursor.s.currentDoc = null;
-        return cb(null, doc);
-      }
-
-      // Return the next object
-      nextObject(cursor, cb);
+      nextObject(this, cb);
     });
   }
 

lib/operations/cursor_ops.js

@@ -106,34 +106,6 @@ function each(cursor, callback) {
   }
 }
 
-/**
- * Check if there is any document still available in the cursor.
- *
- * @method
- * @param {Cursor} cursor The Cursor instance on which to run.
- * @param {Cursor~resultCallback} [callback] The result callback.
- */
-function hasNext(cursor, callback) {
-  if (cursor.s.currentDoc) {
-    return callback(null, true);
-  }
-
-  if (cursor.isNotified()) {
-    return callback(null, false);
-  }
-
-  nextObject(cursor, (err, doc) => {
-    if (err) return callback(err, null);
-    if (cursor.s.state === CursorState.CLOSED || cursor.isDead()) {
-      return callback(null, false);
-    }
-
-    if (!doc) return callback(null, false);
-    cursor.s.currentDoc = doc;
-    callback(null, true);
-  });
-}
-
 // Trampoline emptying the number of retrieved items
 // without incurring a nextTick operation
 function loop(cursor, callback) {
@@ -153,14 +125,6 @@ function loop(cursor, callback) {
  * @param {Cursor~resultCallback} [callback] The result callback.
  */
 function next(cursor, callback) {
-  // Return the currentDoc if someone called hasNext first
-  if (cursor.s.currentDoc) {
-    const doc = cursor.s.currentDoc;
-    cursor.s.currentDoc = null;
-    return callback(null, doc);
-  }
-
-  // Return the next object
   nextObject(cursor, callback);
 }
 
@@ -236,4 +200,4 @@ function toArray(cursor, callback) {
   fetchDocs();
 }
 
-module.exports = { count, each, hasNext, next, toArray };
+module.exports = { count, each, next, toArray };