From 0f50fe2a5e8dd9c21ddf030dcb9ed0550c216d0e Mon Sep 17 00:00:00 2001
From: "Grot (@grafanabot)" <43478413+grafanabot@users.noreply.github.com>
Date: Fri, 17 Jun 2022 08:10:01 -0400
Subject: [PATCH] Expressions: Fixes dashboard schema migration issue that
 casued Expression datasource to be set on panel level (#50945) (#51009)
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* Expressions: Fixes dashboard schema migration issue that casued Expression datasource to be set on panel level

* fixing logic

* Updated

(cherry picked from commit eb25d8df894ac7d0b938bf277d42b67db1541e47)

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>
---
 .../DashExportModal/DashboardExporter.test.ts |  1 +
 .../dashboard/state/DashboardMigrator.test.ts | 32 +++++++++++++++++++
 .../dashboard/state/DashboardMigrator.ts      | 10 +++---
 3 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/public/app/features/dashboard/components/DashExportModal/DashboardExporter.test.ts b/public/app/features/dashboard/components/DashExportModal/DashboardExporter.test.ts
index 5c344340666..e844c8c5175 100644
--- a/public/app/features/dashboard/components/DashExportModal/DashboardExporter.test.ts
+++ b/public/app/features/dashboard/components/DashExportModal/DashboardExporter.test.ts
@@ -345,6 +345,7 @@ describe('given dashboard with repeated panels', () => {
     expect(element.model).toEqual({
       id: 17,
       datasource: { type: 'other2', uid: '$ds' },
+      targets: [{ refId: 'A', datasource: { type: 'other2', uid: '$ds' } }],
       type: 'graph',
     });
   });
diff --git a/public/app/features/dashboard/state/DashboardMigrator.test.ts b/public/app/features/dashboard/state/DashboardMigrator.test.ts
index a2269ab56df..2f0dc793de0 100644
--- a/public/app/features/dashboard/state/DashboardMigrator.test.ts
+++ b/public/app/features/dashboard/state/DashboardMigrator.test.ts
@@ -1993,6 +1993,38 @@ describe('DashboardModel', () => {
       expect(model.panels[0].targets[0].datasource).toEqual({ type: 'prometheus', uid: 'prom2-uid' });
     });
   });
+
+  describe('when migrating default (null) datasource with panel with expressions queries', () => {
+    let model: DashboardModel;
+
+    beforeEach(() => {
+      model = new DashboardModel({
+        panels: [
+          {
+            id: 2,
+            targets: [
+              {
+                refId: 'A',
+              },
+              {
+                refId: 'B',
+                datasource: '__expr__',
+              },
+            ],
+          },
+        ],
+        schemaVersion: 30,
+      });
+    });
+
+    it('should update panel datasource props to default datasource', () => {
+      expect(model.panels[0].datasource).toEqual({ type: 'prometheus', uid: 'prom2-uid' });
+    });
+
+    it('should update target datasource props to default data source', () => {
+      expect(model.panels[0].targets[0].datasource).toEqual({ type: 'prometheus', uid: 'prom2-uid' });
+    });
+  });
 });
 
 function createRow(options: any, panelDescriptions: any[]) {
diff --git a/public/app/features/dashboard/state/DashboardMigrator.ts b/public/app/features/dashboard/state/DashboardMigrator.ts
index 79b747773e9..212f8d273e4 100644
--- a/public/app/features/dashboard/state/DashboardMigrator.ts
+++ b/public/app/features/dashboard/state/DashboardMigrator.ts
@@ -761,15 +761,15 @@ export class DashboardMigrator {
             }
 
             for (const target of panel.targets) {
-              if (target.datasource && panelDataSourceWasDefault) {
+              if (target.datasource == null || target.datasource.uid == null) {
+                target.datasource = { ...panel.datasource };
+              }
+
+              if (panelDataSourceWasDefault && target.datasource.uid !== '__expr__') {
                 // We can have situations when default ds changed and the panel level data source is different from the queries
                 // In this case we use the query level data source as source for truth
                 panel.datasource = target.datasource as DataSourceRef;
               }
-
-              if (target.datasource === null) {
-                target.datasource = getDataSourceRef(defaultDs);
-              }
             }
           }
           return panel;