From d8a83fec9ddcc13722cd799a78cfc0308fbac876 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zolt=C3=A1n=20Bedi?= <zoltan.bedi@gmail.com>
Date: Tue, 30 Mar 2021 19:34:08 +0200
Subject: [PATCH] Prometheus: align exemplars check to latest api change
 (#32513)

---
 .../prometheus/result_transformer.test.ts          | 14 ++++++++++++++
 public/app/plugins/datasource/prometheus/types.ts  |  4 ++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/public/app/plugins/datasource/prometheus/result_transformer.test.ts b/public/app/plugins/datasource/prometheus/result_transformer.test.ts
index 44add64095f..1e47b246fc0 100644
--- a/public/app/plugins/datasource/prometheus/result_transformer.test.ts
+++ b/public/app/plugins/datasource/prometheus/result_transformer.test.ts
@@ -510,6 +510,20 @@ describe('Prometheus Result Transformer', () => {
       expect(result[0].length).toBe(1);
     });
 
+    it('should return with an empty array when data is empty', () => {
+      const result = transform(
+        {
+          data: {
+            status: 'success',
+            data: [],
+          },
+        } as any,
+        options
+      );
+
+      expect(result).toHaveLength(0);
+    });
+
     it('should remove exemplars that are too close to each other', () => {
       const response = {
         status: 'success',
diff --git a/public/app/plugins/datasource/prometheus/types.ts b/public/app/plugins/datasource/prometheus/types.ts
index f5b1c95005c..cdf857d0b8d 100644
--- a/public/app/plugins/datasource/prometheus/types.ts
+++ b/public/app/plugins/datasource/prometheus/types.ts
@@ -63,7 +63,7 @@ export interface PromDataErrorResponse<T = PromData> {
   data: T;
 }
 
-export type PromData = PromMatrixData | PromVectorData | PromScalarData | PromExemplarData[] | null;
+export type PromData = PromMatrixData | PromVectorData | PromScalarData | PromExemplarData[];
 
 export interface Labels {
   [index: string]: any;
@@ -120,7 +120,7 @@ export function isExemplarData(result: PromData): result is PromExemplarData[] {
   if (result == null || !Array.isArray(result)) {
     return false;
   }
-  return 'exemplars' in result[0];
+  return result.length ? 'exemplars' in result[0] : false;
 }
 
 export type MatrixOrVectorResult = PromMatrixData['result'][0] | PromVectorData['result'][0];