Loki: Remove showing of unique labels with the empty string value (#30363)

* Remove empty unique label values

* Add test

* Simplify

packages/grafana-ui/src/components/Logs/LogLabels.test.tsx

@@ -20,4 +20,9 @@ describe('<LogLabels />', () => {
     expect(wrapper.text()).not.toContain('42');
     expect(wrapper.text()).not.toContain('13');
   });
+  it('excludes labels with empty string values', () => {
+    const wrapper = shallow(<LogLabels labels={{ foo: 'bar', baz: '' }} theme={getTheme()} />);
+    expect(wrapper.text()).toContain('bar');
+    expect(wrapper.html()).not.toContain('baz');
+  });
 });

packages/grafana-ui/src/components/Logs/LogLabels.tsx

@@ -59,6 +59,9 @@ export const UnThemedLogLabels: FunctionComponent<Props> = ({ labels, theme }) =
     <span className={cx([styles.logsLabels])}>
       {displayLabels.sort().map(label => {
         const value = labels[label];
+        if (!value) {
+          return;
+        }
         const tooltip = `${label}: ${value}`;
         return (
           <span key={label} className={cx([styles.logsLabel])}>