Add flag to disable prevention of AJAX requests for future requests. Closes #122.

readme.md

@@ -36,6 +36,7 @@ The standard jquery.autocomplete.js file is around 2.7KB when minified via Closu
         * `onSearchError`: `function (query, jqXHR, textStatus, errorThrown) {}` called if ajax request fails. `this` is bound to input element.
         * `onInvalidateSelection`: `function () {}` called when input is altered after selection has been made. `this` is bound to input element.
         * `triggerSelectOnValidInput`: Boolean value indicating if `select` should be triggered if it matches suggestion. Default `true`.
+        * `preventBadQueries`: Boolean value indicating if it shoud prevent future ajax requests for queries with the same root if no results were returned. E.g. if `Jam` returns no suggestions, it will not fire for any future query that starts with `Jam`. Default `true`. 
         * `beforeRender`: `function (container) {}` called before displaying the suggestions. You may manipulate suggestions DOM before it is displayed.
         * `tabDisabled`: Default `false`. Set to true to leave the cursor in the input field after the user tabs to select a suggestion.
         * `paramName`: Default `query`. The name of the request parameter that contains the query.

spec/autocompleteBehavior.js

@@ -597,4 +597,56 @@ describe('Autocomplete', function () {
 
         expect(instance.suggestions.length).toBe(limit);
     });
+
+    it('Should prevent Ajax requests if previous query with matching root failed.', function () {
+        var input = $('<input />'),
+            instance,
+            serviceUrl = '/autocomplete/prevent/ajax',
+            ajaxCount = 0;
+
+        input.autocomplete({
+            serviceUrl: serviceUrl
+        });
+
+        $.mockjax({
+            url: serviceUrl,
+            responseTime: 5,
+            response: function (settings) {
+                ajaxCount++;
+                var response = { suggestions: [] };
+                this.responseText = JSON.stringify(response);
+            }
+        });
+
+        input.val('Jam');
+        instance = input.autocomplete();
+        instance.onValueChange();
+
+        waits(10);
+
+        runs(function (){
+            expect(ajaxCount).toBe(1);
+            input.val('Jama');
+            instance.onValueChange();
+        });
+
+        waits(10);
+
+        runs(function (){
+            // Ajax call should not have bee made:
+            expect(ajaxCount).toBe(1);
+
+            // Change setting and continue:
+            instance.setOptions({ preventBadQueries: false });
+            input.val('Jamai');
+            instance.onValueChange();
+        });
+
+        waits(10);
+
+        runs(function (){
+            // Ajax call should have been made:
+            expect(ajaxCount).toBe(2);
+        });
+    });
 });

src/jquery.autocomplete.js

@@ -76,6 +76,7 @@
                 dataType: 'text',
                 currentRequest: null,
                 triggerSelectOnValidInput: true,
+                preventBadQueries: true,
                 lookupFilter: function (suggestion, originalQuery, queryLowerCase) {
                     return suggestion.value.toLowerCase().indexOf(queryLowerCase) !== -1;
                 },
@@ -515,6 +516,10 @@
         },
 
         isBadQuery: function (q) {
+            if (!this.options.preventBadQueries){
+                return false;
+            }
+
             var badQueries = this.badQueries,
                 i = badQueries.length;
 
@@ -647,8 +652,8 @@
             // Cache results if cache is not disabled:
             if (!options.noCache) {
                 that.cachedResponse[cacheKey] = result;
-                if (result.suggestions.length === 0) {
+                if (options.preventBadQueries && result.suggestions.length === 0) {
-                    that.badQueries.push(cacheKey);
+                    that.badQueries.push(originalQuery);
                 }
             }