GraphNG: don't scan data for min/max when both hard limits are pre-configured (#33295)

packages/grafana-ui/src/components/uPlot/config/UPlotConfigBuilder.test.ts

@@ -281,6 +281,33 @@ describe('UPlotConfigBuilder', () => {
     });
   });
 
+  it('disables autoscaling when both (and only) hardMin and hardMax are specified', () => {
+    const builder = new UPlotConfigBuilder();
+
+    builder.addScale({
+      isTime: false,
+      scaleKey: 'scale-y',
+      orientation: ScaleOrientation.Vertical,
+      direction: ScaleDirection.Up,
+      min: -100,
+      max: 100,
+    });
+
+    expect(builder.getConfig().scales!['scale-y']!.auto).toEqual(false);
+
+    builder.addScale({
+      isTime: false,
+      scaleKey: 'scale-y2',
+      orientation: ScaleOrientation.Vertical,
+      direction: ScaleDirection.Up,
+      min: -100,
+      max: 100,
+      softMin: -50,
+    });
+
+    expect(builder.getConfig().scales!['scale-y2']!.auto).toEqual(true);
+  });
+
   it('allows axes configuration', () => {
     const builder = new UPlotConfigBuilder();
 

packages/grafana-ui/src/components/uPlot/config/UPlotScaleBuilder.ts

@@ -65,15 +65,15 @@ export class UPlotScaleBuilder extends PlotConfigBuilder<ScaleProps, Scale> {
       },
     };
 
+    let hardMinOnly = softMin == null && hardMin != null;
+    let hardMaxOnly = softMax == null && hardMax != null;
+
     // uPlot range function
     const rangeFn = (u: uPlot, dataMin: number, dataMax: number, scaleKey: string) => {
       const scale = u.scales[scaleKey];
 
       let minMax = [dataMin, dataMax];
 
-      let hardMinOnly = softMin == null && hardMin != null;
-      let hardMaxOnly = softMax == null && hardMax != null;
-
       if (scale.distr === 1 || scale.distr === 2) {
         // @ts-ignore here we may use hardMin / hardMax to make sure any extra padding is computed from a more accurate delta
         minMax = uPlot.rangeNum(hardMinOnly ? hardMin : dataMin, hardMaxOnly ? hardMax : dataMax, rangeConfig);
@@ -96,7 +96,7 @@ export class UPlotScaleBuilder extends PlotConfigBuilder<ScaleProps, Scale> {
     return {
       [scaleKey]: {
         time: isTime,
-        auto: !isTime,
+        auto: !isTime && !(hardMinOnly && hardMaxOnly),
         range: range ?? rangeFn,
         dir: direction,
         ori: orientation,