fix: don't push empty originalQuery onto badQueries (#872)

`isBadQuery` matches by prefix: `q.indexOf(bad) === 0`. An empty entry
in `badQueries` matches every subsequent query, silently blocking all
ajax requests after the first empty-query response. Reachable with
`minChars: 0` plus an empty server response.

Guard the push so an empty `originalQuery` never enters the list.

Ports szabto's #845 fix forward to the 2.x TypeScript source.

Closes #845.

Co-authored-by: Tomas Kirda <tomas.kirda@bisoncommerce.com>
Co-authored-by: szabto <szabotamas93@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 4 people

dist/jquery.autocomplete.esm.js

@@ -583,7 +583,7 @@ var _Autocomplete = class _Autocomplete {
     result.suggestions = this.verifySuggestionsFormat(result.suggestions);
     if (!options.noCache) {
       this.cachedResponse[cacheKey] = result;
-      if (options.preventBadQueries && !result.suggestions.length) {
+      if (options.preventBadQueries && !result.suggestions.length && originalQuery) {
         this.badQueries.push(originalQuery);
       }
     }

dist/jquery.autocomplete.js

@@ -591,7 +591,7 @@
       result.suggestions = this.verifySuggestionsFormat(result.suggestions);
       if (!options.noCache) {
         this.cachedResponse[cacheKey] = result;
-        if (options.preventBadQueries && !result.suggestions.length) {
+        if (options.preventBadQueries && !result.suggestions.length && originalQuery) {
           this.badQueries.push(originalQuery);
         }
       }

dist/jquery.autocomplete.min.js

@@ -645,7 +645,11 @@ export class Autocomplete {
 
         if (!options.noCache) {
             this.cachedResponse[cacheKey] = result;
-            if (options.preventBadQueries && !result.suggestions.length) {
+            // Guard against pushing an empty `originalQuery`. `isBadQuery`
+            // matches by prefix (`q.indexOf(bad) === 0`); an empty entry
+            // would match every subsequent query and silently block all
+            // ajax requests after the first empty-query response.
+            if (options.preventBadQueries && !result.suggestions.length && originalQuery) {
                 this.badQueries.push(originalQuery);
             }
         }

src/Autocomplete.ts

@@ -362,6 +362,44 @@ describe("Autocomplete Async — preventBadQueries", () => {
     });
 });
 
+describe("Autocomplete Async — empty originalQuery", () => {
+    it("does not push an empty originalQuery onto badQueries", async () => {
+        const input = $("<input />");
+        const serviceUrl = "/autocomplete/empty-bad-query";
+        let ajaxCount = 0;
+
+        input.autocomplete({
+            serviceUrl,
+            minChars: 0,
+            preventBadQueries: true,
+        });
+        const instance = input.autocomplete();
+
+        $.mockjax({
+            url: serviceUrl,
+            responseTime: 1,
+            response: function () {
+                ajaxCount += 1;
+                this.responseText = JSON.stringify({ suggestions: [] });
+            },
+        });
+
+        // First lookup: empty query with no results.
+        input.val("");
+        instance.onValueChange();
+        await new Promise((r) => setTimeout(r, 30));
+
+        // Second lookup: real query — must not be short-circuited by an empty
+        // prefix sitting in badQueries.
+        input.val("Jam");
+        instance.onValueChange();
+        await new Promise((r) => setTimeout(r, 30));
+
+        expect(instance.badQueries).not.toContain("");
+        expect(ajaxCount).toBe(2);
+    });
+});
+
 describe("Autocomplete", () => {
     afterEach(() => {
         $(".autocomplete-suggestions").hide();