Fixes #81465: Exclude-null now it's getting initialized properly by default (#85613)

* fix #81465 (FilterByValueTransformerEditor.tsx): Exclude-null now it's getting initialised properly by default

The default matcher of a new filter by value condition has been changed from greater to isNull. Added a file FilterByValueTransformerEditor.test.tsx with a test to confirm this change

* update tests and run linter

* filter-by-values-exclude-null/ update test definition

---------

Co-authored-by: jev forsberg <jev.forsberg@grafana.com>

public/app/features/transformers/FilterByValueTransformer/FilterByValueTransformerEditor.test.tsx

@@ -0,0 +1,70 @@
+import { render, fireEvent } from '@testing-library/react';
+import React from 'react';
+
+import { DataFrame, FieldType, ValueMatcherID, valueMatchers } from '@grafana/data';
+import { FilterByValueMatch, FilterByValueType } from '@grafana/data/src/transformations/transformers/filterByValue';
+
+import { FilterByValueTransformerEditor } from './FilterByValueTransformerEditor';
+
+describe('FilterByValueTransformerEditor', () => {
+  it('correctly applies the default isNull option when onAddFilter is first called', () => {
+    // Mock onChange function
+    const onChangeMock = jest.fn();
+
+    // Mock options
+    const options = {
+      type: FilterByValueType.include,
+      match: FilterByValueMatch.all,
+      filters: [],
+    };
+
+    // Mock input
+    const input: DataFrame[] = [
+      {
+        fields: [
+          {
+            name: 'person',
+            type: FieldType.string,
+            config: { displayName: 'Person' },
+            values: ['john', 'jill', 'jeremy', ''],
+          },
+          {
+            name: 'city',
+            type: FieldType.string,
+            config: { displayName: 'City' },
+            values: ['london', 'budapest', '', 'lisbon'],
+          },
+        ],
+        length: 4,
+      },
+    ];
+
+    // Render the component
+    const { getByText } = render(
+      <FilterByValueTransformerEditor input={input} options={options} onChange={onChangeMock} />
+    );
+
+    // Find and click the "Add condition" button
+    fireEvent.click(getByText('Add condition'));
+
+    // Check if onChange was called with the correct filter
+    expect(onChangeMock).toHaveBeenCalledWith({
+      filters: [
+        {
+          fieldName: 'Person',
+          config: {
+            id: ValueMatcherID.isNull,
+            options: valueMatchers.get(ValueMatcherID.isNull).getDefaultOptions({
+              name: 'person',
+              type: FieldType.string,
+              config: { displayName: 'Person' },
+              values: ['john', 'jill', 'jeremy', ''],
+            }),
+          },
+        },
+      ],
+      match: FilterByValueMatch.all,
+      type: FilterByValueType.include,
+    });
+  });
+});

public/app/features/transformers/FilterByValueTransformer/FilterByValueTransformerEditor.tsx

@@ -49,7 +49,7 @@ export const FilterByValueTransformerEditor = (props: TransformerUIProps<FilterB
     }
 
     const filters = cloneDeep(options.filters);
-    const matcher = valueMatchers.get(ValueMatcherID.greater);
+    const matcher = valueMatchers.get(ValueMatcherID.isNull);
 
     filters.push({
       fieldName: getFieldDisplayName(field, frame, input),