Loki: Fix labels in LabelBrowser being wrongly cached (#64482)

* remove label cache from label browser

* fix spelling

Co-authored-by: Gareth Dawson <gareth.dawson@grafana.com>

---------

Co-authored-by: Gareth Dawson <gareth.dawson@grafana.com>

public/app/plugins/datasource/loki/LanguageProvider.test.ts

@@ -274,6 +274,40 @@ describe('Request URL', () => {
   });
 });
 
+describe('fetchLabels', () => {
+  it('should return labels', async () => {
+    const datasourceWithLabels = setup({ other: [] });
+
+    const instance = new LanguageProvider(datasourceWithLabels);
+    const labels = await instance.fetchLabels();
+    expect(labels).toEqual(['other']);
+  });
+
+  it('should set labels', async () => {
+    const datasourceWithLabels = setup({ other: [] });
+
+    const instance = new LanguageProvider(datasourceWithLabels);
+    await instance.fetchLabels();
+    expect(instance.labelKeys).toEqual(['other']);
+  });
+
+  it('should return empty array', async () => {
+    const datasourceWithLabels = setup({});
+
+    const instance = new LanguageProvider(datasourceWithLabels);
+    const labels = await instance.fetchLabels();
+    expect(labels).toEqual([]);
+  });
+
+  it('should set empty array', async () => {
+    const datasourceWithLabels = setup({});
+
+    const instance = new LanguageProvider(datasourceWithLabels);
+    await instance.fetchLabels();
+    expect(instance.labelKeys).toEqual([]);
+  });
+});
+
 describe('Query imports', () => {
   const datasource = setup({});
 

public/app/plugins/datasource/loki/LanguageProvider.ts

@@ -380,6 +380,7 @@ export default class LokiLanguageProvider extends LanguageProvider {
         .sort()
         .filter((label) => label !== '__name__');
       this.labelKeys = labels;
+      return this.labelKeys;
     }
 
     return [];

public/app/plugins/datasource/loki/querybuilder/components/LabelBrowserModal.tsx

@@ -33,9 +33,9 @@ export const LabelBrowserModal = (props: Props) => {
       return;
     }
 
-    datasource.languageProvider.start().then(() => {
+    datasource.languageProvider.fetchLabels().then((labels) => {
       setLabelsLoaded(true);
-      setHasLogLabels(datasource.languageProvider.getLabelKeys().length > 0);
+      setHasLogLabels(labels.length > 0);
     });
   }, [datasource, isOpen]);