Modified limitRequest to allow negative limits to pass through to Mongo. Appropriate tests added.

Author: madtimber

lib/mongodb/cursor.js

@@ -316,11 +316,12 @@ Cursor.prototype.batchSize = function(batchSize, callback) {
  */
 var limitRequest = function(self) {
   var requestedLimit = self.limitValue;
-
-  if(self.limitValue > 0) {
-    if (self.batchSizeValue > 0) {
-      requestedLimit = self.limitValue < self.batchSizeValue ?
-        self.limitValue : self.batchSizeValue;
+  var absLimitValue = Math.abs(self.limitValue);
+  var absBatchValue = Math.abs(self.batchSizeValue);
+  
+  if(absLimitValue > 0) {
+    if (absBatchValue > 0) {
+      requestedLimit = Math.min(absLimitValue, absBatchValue);
     }
   } else {
     requestedLimit = self.batchSizeValue;

test/cursor_test.js

@@ -439,6 +439,66 @@ exports.shouldCorrectlyHandleLimitOnCursor = function(test) {
   });
 }
 
+/**
+ * @ignore
+ * @api private
+ */
+exports.shouldCorrectlyHandleNegativeOneLimitOnCursor = function(test) {
+  client.createCollection('test_cursor_negative_one_limit', function(err, collection) {
+    Step(
+      function insert() {
+        var group = this.group();
+
+        for(var i = 0; i < 10; i++) {
+          collection.save({'x':1}, {safe:true}, group());
+        }
+      }, 
+
+      function finished() {
+        collection.find(function(err, cursor) {
+          cursor.limit(-1, function(err, cursor) {
+            cursor.toArray(function(err, items) {
+              test.equal(1, items.length);
+              // Let's close the db
+              test.done();
+            });
+          });
+        });
+      }
+    );
+  });
+}
+
+/**
+ * @ignore
+ * @api private
+ */
+exports.shouldCorrectlyHandleAnyNegativeLimitOnCursor = function(test) {
+  client.createCollection('test_cursor_any_negative_limit', function(err, collection) {
+    Step(
+      function insert() {
+        var group = this.group();
+
+        for(var i = 0; i < 10; i++) {
+          collection.save({'x':1}, {safe:true}, group());
+        }
+      }, 
+
+      function finished() {
+        collection.find(function(err, cursor) {
+          cursor.limit(-5, function(err, cursor) {
+            cursor.toArray(function(err, items) {
+              test.equal(5, items.length);
+              // Let's close the db
+              test.done();
+            });
+          });
+        });
+      }
+    );
+  });
+}
+
 /**
  * @ignore
  * @api private