fix(filters): correct null matching logic [CW-5741] (#12627)

This PR fixes a bug came from assuming the old null check only mattered
for the `is_not_present` filter.

The fix keeps `not_equal_to` working but lets each operator decide what
to do with `null`. Presence filters look at a shared `isNullish` flag,
text filters still rely on `contains`, and date filters skip
conversations with no timestamp. The new spec covers the null-assignee
scenario for both `equal_to` and `not_equal_to` so we don’t miss this
again.

app/javascript/dashboard/store/modules/conversations/helpers/filterHelpers.js

@@ -154,7 +154,10 @@ const equalTo = (filterValue, conversationValue) => {
  * It only works with string values and returns false for non-string types.
  */
 const contains = (filterValue, conversationValue) => {
-  if (typeof conversationValue === 'string') {
+  if (
+    typeof conversationValue === 'string' &&
+    typeof filterValue === 'string'
+  ) {
     return conversationValue.toLowerCase().includes(filterValue.toLowerCase());
   }
   return false;
@@ -190,10 +193,8 @@ const compareDates = (conversationValue, filterValue, compareFn) => {
 const matchesCondition = (conversationValue, filter) => {
   const { filter_operator: filterOperator, values } = filter;
 
-  // Handle null/undefined values
-  if (conversationValue === null || conversationValue === undefined) {
-    return filterOperator === 'is_not_present';
-  }
+  const isNullish =
+    conversationValue === null || conversationValue === undefined;
 
   const filterValue = Array.isArray(values)
     ? values.map(resolveValue)
@@ -213,10 +214,10 @@ const matchesCondition = (conversationValue, filter) => {
       return !contains(filterValue, conversationValue);
 
     case 'is_present':
-      return true; // We already handled null/undefined above
+      return !isNullish;
 
     case 'is_not_present':
-      return false; // We already handled null/undefined above
+      return isNullish;
 
     case 'is_greater_than':
       return compareDates(conversationValue, filterValue, (a, b) => a > b);
@@ -225,6 +226,10 @@ const matchesCondition = (conversationValue, filter) => {
       return compareDates(conversationValue, filterValue, (a, b) => a < b);
 
     case 'days_before': {
+      if (isNullish) {
+        return false;
+      }
+
       const today = new Date();
       const daysInMilliseconds = filterValue * 24 * 60 * 60 * 1000;
       const targetDate = new Date(today.getTime() - daysInMilliseconds);

app/javascript/dashboard/store/modules/conversations/helpers/specs/filterHelpers.spec.js

@@ -192,6 +192,32 @@ describe('filterHelpers', () => {
       expect(matchesFilters(conversation, filters)).toBe(true);
     });
 
+    it('should not match conversation with equal_to operator when assignee is null', () => {
+      const conversation = { meta: { assignee: null } };
+      const filters = [
+        {
+          attribute_key: 'assignee_id',
+          filter_operator: 'equal_to',
+          values: { id: 1, name: 'John Doe' },
+          query_operator: 'and',
+        },
+      ];
+      expect(matchesFilters(conversation, filters)).toBe(false);
+    });
+
+    it('should match conversation with not_equal_to operator when assignee is null', () => {
+      const conversation = { meta: { assignee: null } };
+      const filters = [
+        {
+          attribute_key: 'assignee_id',
+          filter_operator: 'not_equal_to',
+          values: { id: 1, name: 'John Doe' },
+          query_operator: 'and',
+        },
+      ];
+      expect(matchesFilters(conversation, filters)).toBe(true);
+    });
+
     it('should match conversation with is_not_present operator for assignee_id', () => {
       const conversation = { meta: { assignee: null } };
       const filters = [
@@ -285,6 +311,58 @@ describe('filterHelpers', () => {
       expect(matchesFilters(conversation, filters)).toBe(false);
     });
 
+    it('should not match contains operator when display_id is null', () => {
+      const conversation = { id: null };
+      const filters = [
+        {
+          attribute_key: 'display_id',
+          filter_operator: 'contains',
+          values: '234',
+          query_operator: 'and',
+        },
+      ];
+      expect(matchesFilters(conversation, filters)).toBe(false);
+    });
+
+    it('should not match contains operator when filter value is null', () => {
+      const conversation = { id: '12345' };
+      const filters = [
+        {
+          attribute_key: 'display_id',
+          filter_operator: 'contains',
+          values: null,
+          query_operator: 'and',
+        },
+      ];
+      expect(matchesFilters(conversation, filters)).toBe(false);
+    });
+
+    it('should match does_not_contain operator when display_id is null', () => {
+      const conversation = { id: null };
+      const filters = [
+        {
+          attribute_key: 'display_id',
+          filter_operator: 'does_not_contain',
+          values: '234',
+          query_operator: 'and',
+        },
+      ];
+      expect(matchesFilters(conversation, filters)).toBe(true);
+    });
+
+    it('should match does_not_contain operator when filter value is null', () => {
+      const conversation = { id: '12345' };
+      const filters = [
+        {
+          attribute_key: 'display_id',
+          filter_operator: 'does_not_contain',
+          values: null,
+          query_operator: 'and',
+        },
+      ];
+      expect(matchesFilters(conversation, filters)).toBe(true);
+    });
+
     it('should match conversation with does_not_contain operator when value is not present', () => {
       const conversation = { id: '12345' };
       const filters = [