Fixes #15477

public/app/features/dashboard/state/PanelModel.test.ts

@@ -10,6 +10,20 @@ describe('PanelModel', () => {
         type: 'table',
         showColumns: true,
         targets: [{ refId: 'A' }, { noRefId: true }],
+        options: {
+          thresholds: [
+            {
+              color: '#F2495C',
+              index: 1,
+              value: 50,
+            },
+            {
+              color: '#73BF69',
+              index: 0,
+              value: null,
+            },
+          ],
+        },
       });
     });
 
@@ -35,6 +49,21 @@ describe('PanelModel', () => {
       expect(saveModel.events).toBe(undefined);
     });
 
+    it('should restore -Infinity value for base threshold', () => {
+      expect(model.options.thresholds).toEqual([
+        {
+          color: '#F2495C',
+          index: 1,
+          value: 50,
+        },
+        {
+          color: '#73BF69',
+          index: 0,
+          value: -Infinity,
+        },
+      ]);
+    });
+
     describe('when changing panel type', () => {
       beforeEach(() => {
         model.changeType('graph', true);

public/app/features/dashboard/state/PanelModel.ts

@@ -3,7 +3,7 @@ import _ from 'lodash';
 
 // Types
 import { Emitter } from 'app/core/utils/emitter';
-import { DataQuery, TimeSeries } from '@grafana/ui';
+import { DataQuery, TimeSeries, Threshold } from '@grafana/ui';
 import { TableData } from '@grafana/ui/src';
 
 export interface GridPos {
@@ -91,7 +91,9 @@ export class PanelModel {
   timeFrom?: any;
   timeShift?: any;
   hideTimeOverride?: any;
-  options: object;
+  options: {
+    [key: string]: any;
+  };
 
   maxDataPoints?: number;
   interval?: string;
@@ -119,6 +121,8 @@ export class PanelModel {
     _.defaultsDeep(this, _.cloneDeep(defaults));
     // queries must have refId
     this.ensureQueryIds();
+
+    this.restoreInfintyForThresholds();
   }
 
   ensureQueryIds() {
@@ -131,6 +135,19 @@ export class PanelModel {
     }
   }
 
+  restoreInfintyForThresholds() {
+    if (this.options && this.options.thresholds) {
+      this.options.thresholds = this.options.thresholds.map((threshold: Threshold) => {
+        // JSON serialization of -Infinity is 'null' so lets convert it back to -Infinity
+        if (threshold.index === 0 && threshold.value === null) {
+          return { ...threshold, value: -Infinity };
+        }
+
+        return threshold;
+      });
+    }
+  }
+
   getOptions(panelDefaults) {
     return _.defaultsDeep(this.options || {}, panelDefaults);
   }