Loki Context UI: Do not disable last label (#62866)

* improved text

* prevent all labels removed

* use `structuredClone` instead of lodash

* update test

* get `structuredClone` in test?

* fix using structuredClone

.betterer.results

@@ -5998,6 +5998,11 @@ exports[`better eslint`] = {
     "public/app/plugins/datasource/loki/LiveStreams.ts:5381": [
       [0, 0, 0, "Unexpected any. Specify a different type.", "0"]
     ],
+    "public/app/plugins/datasource/loki/components/LokiContextUi.test.tsx:5381": [
+      [0, 0, 0, "Unexpected any. Specify a different type.", "0"],
+      [0, 0, 0, "Unexpected any. Specify a different type.", "1"],
+      [0, 0, 0, "Unexpected any. Specify a different type.", "2"]
+    ],
     "public/app/plugins/datasource/loki/components/LokiLabelBrowser.tsx:5381": [
       [0, 0, 0, "Do not use any type assertions.", "0"],
       [0, 0, 0, "Do not use any type assertions.", "1"]

public/app/plugins/datasource/loki/components/LokiContextUi.test.tsx

@@ -15,6 +15,20 @@ jest.mock('@grafana/runtime', () => ({
 }));
 
 describe('LokiContextUi', () => {
+  const savedGlobal = global;
+  beforeAll(() => {
+    // TODO: `structuredClone` is not yet in jsdom https://github.com/jsdom/jsdom/issues/3363
+    if (!(global as any).structuredClone) {
+      (global as any).structuredClone = function structuredClone(objectToClone: any) {
+        const stringified = JSON.stringify(objectToClone);
+        const parsed = JSON.parse(stringified);
+        return parsed;
+      };
+    }
+  });
+  afterAll(() => {
+    global = savedGlobal;
+  });
   const setupProps = (): LokiContextUiProps => {
     const mockLanguageProvider = {
       start: jest.fn().mockImplementation(() => Promise.resolve()),
@@ -66,7 +80,7 @@ describe('LokiContextUi', () => {
     render(<LokiContextUi {...props} />);
 
     // Initial set of labels is available and not selected
-    expect(await screen.findByText(/Select labels to include in the context query/)).toBeInTheDocument();
+    expect(await screen.findByText(/Select labels to be included in the context query/)).toBeInTheDocument();
   });
 
   it('starts the languageProvider', async () => {

public/app/plugins/datasource/loki/components/LokiContextUi.tsx

@@ -49,9 +49,11 @@ export function LokiContextUi(props: LokiContextUiProps) {
   const styles = useStyles2(getStyles);
 
   const [contextFilters, setContextFilters] = useState<ContextFilter[]>([]);
+
   const [initialized, setInitialized] = useState(false);
   const timerHandle = React.useRef<number>();
   const previousInitialized = React.useRef<boolean>(false);
+  const previousContextFilters = React.useRef<ContextFilter[]>([]);
   useEffect(() => {
     if (!initialized) {
       return;
@@ -63,6 +65,13 @@ export function LokiContextUi(props: LokiContextUiProps) {
       return;
     }
 
+    if (contextFilters.filter(({ enabled, fromParser }) => enabled && !fromParser).length === 0) {
+      setContextFilters(previousContextFilters.current);
+      return;
+    }
+
+    previousContextFilters.current = structuredClone(contextFilters);
+
     if (timerHandle.current) {
       clearTimeout(timerHandle.current);
     }
@@ -143,7 +152,7 @@ export function LokiContextUi(props: LokiContextUiProps) {
             colorIndex={1}
           />
         </Tooltip>{' '}
-        Select labels to include in the context query:
+        Select labels to be included in the context query:
       </div>
       <div>
         <MultiSelect