Prometheus: Fix ad hoc filters when using explore table column filtering (#111141)

* add support for ad hoc filtering from explore

* fix test

* remove helper function and keep check in if statement

packages/grafana-prometheus/src/add_label_to_query.test.ts

@@ -66,6 +66,15 @@ describe('addLabelToQuery()', () => {
     );
   });
 
+  it('should modify existing labels if the operator is different', () => {
+    expect(addLabelToQuery(addLabelToQuery('foo{x="yy"}', 'bar', 'baz', '!='), 'bar', 'baz', '=')).toBe(
+      'foo{x="yy", bar="baz"}'
+    );
+    expect(addLabelToQuery(addLabelToQuery('foo{x="yy"}', 'bar', 'baz', '='), 'bar', 'baz', '!=')).toBe(
+      'foo{x="yy", bar!="baz"}'
+    );
+  });
+
   it('should not remove filters', () => {
     expect(addLabelToQuery('{x="y"} |="yy"', 'bar', 'baz')).toBe('{x="y", bar="baz"} |="yy"');
     expect(addLabelToQuery('{x="y"} |="yy" !~"xx"', 'bar', 'baz')).toBe('{x="y", bar="baz"} |="yy" !~"xx"');

packages/grafana-prometheus/src/add_label_to_query.ts

@@ -79,8 +79,17 @@ function addFilter(
     const start = query.substring(prev, match.from);
     const end = isLast ? query.substring(match.to) : '';
 
-    if (!labelExists(match.query.labels, filter)) {
+    const labelToMatch = labelExists(match.query.labels, filter);
+    if (labelToMatch) {
+      // if label exists, check the operator, if it is different, update it.
       // We don't want to add duplicate labels.
+      if (labelToMatch.op !== filter.op) {
+        match.query.labels = match.query.labels.map((label) =>
+          label.label === filter.label && label.value === filter.value ? filter : label
+        );
+      }
+    } else {
+      // label does not exist, add as is.
       match.query.labels.push(filter);
     }
     const newLabels = renderQuery(match.query);