Stops milestone being editable by backspace

app/assets/javascripts/boards/boards_bundle.js

@@ -76,7 +76,7 @@ $(() => {
 
       gl.boardService = new BoardService(this.endpoint, this.bulkUpdatePath, this.boardId);
 
-      gl.boardsFilterManager = new FilteredSearchBoards(Store.filter, true);
+      gl.boardsFilterManager = new FilteredSearchBoards(Store.filter, true, [(this.milestoneTitle ? 'milestone' : null)]);
     },
     mounted () {
       Store.disabled = this.disabled;

app/assets/javascripts/boards/filtered_search_boards.js

 export default class FilteredSearchBoards extends gl.FilteredSearchManager {
-  constructor(store, updateUrl = false) {
+  constructor(store, updateUrl = false, cantEdit = []) {
     super('boards');
 
     this.store = store;
     this.updateUrl = updateUrl;
     this.isHandledAsync = true;
+    this.cantEdit = cantEdit;
   }
 
   updateObject(path) {
@@ -28,4 +29,10 @@ export default class FilteredSearchBoards extends gl.FilteredSearchManager {
     // Get the placeholder back if search is empty
     this.filteredSearchInput.dispatchEvent(new Event('input'));
   }
+
+  canEdit(token) {
+    const tokenName = token.querySelector('.name').textContent.trim();
+
+    return this.cantEdit.indexOf(tokenName) === -1;
+  }
 }

app/assets/javascripts/filtered_search/filtered_search_manager.js

@@ -84,6 +84,8 @@
         const { lastVisualToken } = gl.FilteredSearchVisualTokens.getLastVisualTokenBeforeInput();
 
         if (this.filteredSearchInput.value === '' && lastVisualToken) {
+          if (this.canEdit && !this.canEdit(lastVisualToken)) return;
+
           this.filteredSearchInput.value = gl.FilteredSearchVisualTokens.getLastTokenPartial();
           gl.FilteredSearchVisualTokens.removeLastTokenPartial();
         }