Fixed bug replacing full input value

app/assets/javascripts/filtered_search/dropdown_utils.js.es6

@@ -89,9 +89,15 @@
     static getInputSelectionPosition(input) {
       const inputValue = input.value;
       const selectionStart = input.selectionStart;
-      const left = inputValue.slice(0, selectionStart + 1).search(/\S+$/);
+      let left = inputValue.slice(0, selectionStart + 1).search(/\S+$/);
       const right = inputValue.slice(selectionStart).search(/\s/);
+      if (selectionStart === 0) {
+        left = 0;
+      } else if (selectionStart === inputValue.length && left < 0) {
+        left = inputValue.length;
+      }
+
       return {
         left,
         right,

app/assets/javascripts/filtered_search/filtered_search_dropdown_manager.js.es6

@@ -62,16 +62,13 @@
       // Get the string to replace
       const selectionStart = input.selectionStart;
-      let { left, right } = gl.DropdownUtils.getInputSelectionPosition(input);
+      const { left } = gl.DropdownUtils.getInputSelectionPosition(input);
+      let { right } = gl.DropdownUtils.getInputSelectionPosition(input);
       if (right < 0) {
         right = inputValue.length;
       }
-      if (left < 0) {
-        left += 1;
-      }
-
       input.value = `${inputValue.substr(0, left)}${word}${inputValue.substr(right + selectionStart)}`;
       gl.FilteredSearchDropdownManager.updateInputCaretPosition(selectionStart, input);
     }