fix board filter parsing - don't replace encoded + symbols with spaces

app/assets/javascripts/boards/utils/query_data.js

@@ -5,7 +5,7 @@ export default (path, extraData) => path.split('&').reduce((dataParam, filterPar
   const paramSplit = filterParam.split('=');
   const paramKeyNormalized = paramSplit[0].replace('[]', '');
   const isArray = paramSplit[0].indexOf('[]');
-  const value = decodeURIComponent(paramSplit[1]).replace(/\+/g, ' ');
+  const value = decodeURIComponent(paramSplit[1].replace(/\+/g, ' '));
 
   if (isArray !== -1) {
     if (!data[paramKeyNormalized]) {

changelogs/unreleased/34252-trailing-plus.yml

+---
+title: allow trailing + on labels in board filters
+merge_request:
+author:
+type: fixed

spec/javascripts/boards/utils/query_data_spec.js

+import queryData from '~/boards/utils/query_data';
+
+describe('queryData', () => {
+  it('parses path for label with trailing +', () => {
+    const path = 'label_name[]=label%2B';
+    expect(
+      queryData(path, {}),
+    ).toEqual({
+      label_name: ['label+'],
+    });
+  });
+
+  it('parses path for milestone with trailing +', () => {
+    const path = 'milestone_title=A%2B';
+    expect(
+      queryData(path, {}),
+    ).toEqual({
+      milestone_title: 'A+',
+    });
+  });
+});