Fix point size scaling when filtering to single value

superset-frontend/plugins/geoset-map-chart/src/components/Legend.tsx

@@ -103,6 +103,9 @@ export type SizeLegend = {
   endSize: number;
   valueColumn: string;
   legendTitle?: string;
+  legendName?: string;
+  /** Actual computed color of the single remaining point (when noSizeRange). */
+  singleValueColor?: RGBAColor;
   usesPercentBounds?: boolean;
 };
 
@@ -154,6 +157,23 @@ const Legend = ({
     return formatNumber(d3Format, numValue);
   };
 
+  /** Render a Swatch + label row for single-value size legends. */
+  const renderSingleValueRow = (
+    swatchFill: RGBAColor,
+    swatchStroke: RGBAColor,
+    label: string,
+  ) => (
+    <div style={{ display: 'flex', alignItems: 'center', gap: 6 }}>
+      <Swatch
+        fill={swatchFill}
+        stroke={swatchStroke}
+        icon={icon}
+        geometryType={geometryType}
+      />
+      <span>{label}</span>
+    </div>
+  );
+
   // --- Render metric legend if present and not forcing categorical ---
   const metricLegendContent = metricLegend ? (
     <div className="metric-legend">
@@ -190,8 +210,8 @@ const Legend = ({
   ) : null;
 
   // --- Render size legend if present ---
-  const sizeLegendContent =
-    sizeLegend && sizeLegend.startSize !== sizeLegend.endSize ? (
+  const sizeLegendContent = sizeLegend ? (
+    sizeLegend.startSize !== sizeLegend.endSize ? (
       <div className="metric-legend">
         <div className="legend-title">
           {sizeLegend.legendTitle || toTitleCase(sizeLegend.valueColumn)}
@@ -207,7 +227,24 @@ const Legend = ({
           usesPercentBounds={sizeLegend.usesPercentBounds}
         />
       </div>
-    ) : null;
+    ) : (
+      // Single-value fallback: show a standard entry instead of graduated icons
+      <div className="metric-legend">
+        <div className="legend-title">
+          {sizeLegend.legendTitle || toTitleCase(sizeLegend.valueColumn)}
+        </div>
+        {renderSingleValueRow(
+          sizeLegend.singleValueColor ??
+            metricLegend?.startColor ??
+            fillColor,
+          sizeLegend.singleValueColor ??
+            metricLegend?.startColor ??
+            strokeColor,
+          sizeLegend.legendName || toTitleCase(sizeLegend.valueColumn),
+        )}
+      </div>
+    )
+  ) : null;
 
   // --- Combined metric+size: 4 gradient-colored circles replacing gradient bar + size circles ---
   const combinedMetricSizeContent =
@@ -218,15 +255,25 @@ const Legend = ({
             metricLegend.legendName ||
             toTitleCase(sizeLegend.valueColumn)}
         </div>
-        <GraduatedIcons
-          responsive
-          lower={sizeLegend.lower}
-          upper={sizeLegend.upper}
-          startColor={metricLegend.startColor}
-          endColor={metricLegend.endColor}
-          icon={icon}
-          usesPercentBounds={sizeLegend.usesPercentBounds}
-        />
+        {sizeLegend.startSize !== sizeLegend.endSize ? (
+          <GraduatedIcons
+            responsive
+            lower={sizeLegend.lower}
+            upper={sizeLegend.upper}
+            startColor={metricLegend.startColor}
+            endColor={metricLegend.endColor}
+            icon={icon}
+            usesPercentBounds={sizeLegend.usesPercentBounds}
+          />
+        ) : (
+          renderSingleValueRow(
+            sizeLegend.singleValueColor ?? metricLegend.startColor,
+            sizeLegend.singleValueColor ?? metricLegend.startColor,
+            sizeLegend.legendName ||
+              metricLegend.legendName ||
+              toTitleCase(sizeLegend.valueColumn),
+          )
+        )}
       </div>
     ) : null;
 

superset-frontend/plugins/geoset-map-chart/src/components/MultiLegend.tsx

@@ -234,12 +234,26 @@ const LegendEntryContent: React.FC<{
 
   const { fill, stroke } = getDefaultColors(legendEntry);
 
+  /** Render a single-value size swatch (used when startSize === endSize). */
+  const singleValueSizeRow = legendEntry.sizeEntry ? (
+    <CategoryRow>
+      <Swatch
+        fill={legendEntry.sizeEntry.singleValueColor ?? fill}
+        stroke={legendEntry.sizeEntry.singleValueColor ?? stroke}
+        icon={legendEntry.icon}
+        geometryType={legendEntry.geometryType}
+      />
+      <div>{legendEntry.legendName}</div>
+    </CategoryRow>
+  ) : null;
+
   return (
     <div>
-      {/* SIMPLE - show icon and slice name (skip when sizeEntry handles the display) */}
+      {/* SIMPLE - show icon and slice name (skip when sizeEntry with a range handles the display) */}
       {legendEntry.type === 'simple' &&
         legendEntry.simpleStyle &&
-        !legendEntry.sizeEntry && (
+        (!legendEntry.sizeEntry ||
+          legendEntry.sizeEntry.startSize === legendEntry.sizeEntry.endSize) && (
           <CategoryRow>
             {showEntryCheckbox && (
               <VisibilityCheckbox
@@ -344,7 +358,7 @@ const LegendEntryContent: React.FC<{
       {legendEntry.isCombinedMetricSize &&
         legendEntry.metric &&
         legendEntry.sizeEntry &&
-        legendEntry.sizeEntry.startSize !== legendEntry.sizeEntry.endSize && (
+        (legendEntry.sizeEntry.startSize !== legendEntry.sizeEntry.endSize ? (
           <GraduatedIcons
             lower={legendEntry.sizeEntry.lower}
             upper={legendEntry.sizeEntry.upper}
@@ -353,7 +367,9 @@ const LegendEntryContent: React.FC<{
             icon={legendEntry.icon}
             usesPercentBounds={legendEntry.sizeEntry.usesPercentBounds}
           />
-        )}
+        ) : (
+          singleValueSizeRow
+        ))}
 
       {/* METRIC GRADIENT — only when NOT combined */}
       {!legendEntry.isCombinedMetricSize && legendEntry.metric && (
@@ -407,7 +423,7 @@ const LegendEntryContent: React.FC<{
       {!legendEntry.isCombinedMetricSize &&
         !(legendEntry.categories && legendEntry.categories.length > 0) &&
         legendEntry.sizeEntry &&
-        legendEntry.sizeEntry.startSize !== legendEntry.sizeEntry.endSize && (
+        (legendEntry.sizeEntry.startSize !== legendEntry.sizeEntry.endSize ? (
           <GraduatedIcons
             lower={legendEntry.sizeEntry.lower}
             upper={legendEntry.sizeEntry.upper}
@@ -417,7 +433,9 @@ const LegendEntryContent: React.FC<{
             icon={legendEntry.icon}
             usesPercentBounds={legendEntry.sizeEntry.usesPercentBounds}
           />
-        )}
+        ) : (
+          singleValueSizeRow
+        ))}
     </div>
   );
 };

superset-frontend/plugins/geoset-map-chart/src/transformProps.ts

@@ -255,7 +255,18 @@ export default function transformProps(chartProps: ChartProps) {
     );
 
     if (bounds) {
-      const { lower, upper, usesPercentBounds } = bounds;
+      const { sortedValues, lower, upper, usesPercentBounds } = bounds;
+
+      // Detect when all data points share the same size value (e.g. dashboard
+      // filter reduced to a single point).
+      const uniqueMin = sortedValues[0];
+      const uniqueMax = sortedValues[sortedValues.length - 1];
+      const noSizeRange = uniqueMin === uniqueMax;
+
+      // The scale always uses the original startSize/endSize so the point
+      // keeps its natural size on the configured range.  When lower === upper
+      // (no explicit bounds), computeSizeScale's range === 0 guard returns
+      // the midpoint automatically.
       sizeScale = computeSizeScale(
         {
           valueColumn: sizeValueColumn,
@@ -266,15 +277,37 @@ export default function transformProps(chartProps: ChartProps) {
         },
         [lower, upper],
       );
+
+      // The legend collapses startSize/endSize to the midpoint when there's
+      // no data variation, which suppresses graduated icons (nothing to
+      // differentiate).
+      const midSize = Math.round((startSize + endSize) / 2);
+      const legendStartSize = noSizeRange ? midSize : startSize;
+      const legendEndSize = noSizeRange ? midSize : endSize;
+
       sizeLegend = {
         lower,
         upper,
-        startSize,
-        endSize,
+        startSize: legendStartSize,
+        endSize: legendEndSize,
         valueColumn: sizeValueColumn,
         legendTitle: legend?.title,
+        legendName: legend?.name || legend?.title || sizeValueColumn,
         usesPercentBounds,
       };
+
+      // When there's a single unique value and metric coloring is active,
+      // compute the actual rendered color so the legend swatch matches the
+      // point on the map (startColor is only the gradient start, not the
+      // actual color at the point's position in the range).
+      if (noSizeRange && metricColorScale && colorByValue?.valueColumn) {
+        const metricVal = Number(
+          rawData[0]?.[colorByValue.valueColumn] ?? NaN,
+        );
+        if (!Number.isNaN(metricVal)) {
+          sizeLegend.singleValueColor = metricColorScale(metricVal) as RGBAColor;
+        }
+      }
     }
   }
 

superset-frontend/plugins/geoset-map-chart/src/utils/colors.ts

@@ -84,8 +84,8 @@ export function computeSizeScale(
   const upper = config.upperBound ?? max;
   const range = upper - lower;
   return (val: number) => {
-    if (val == null || Number.isNaN(val) || range === 0)
-      return config.startSize;
+    if (val == null || Number.isNaN(val)) return config.startSize;
+    if (range === 0) return Math.round((config.startSize + config.endSize) / 2);
     const t = Math.max(0, Math.min(1, (val - lower) / range));
     return Math.round(
       config.startSize + t * (config.endSize - config.startSize),

superset-frontend/plugins/geoset-map-chart/test/components/Legend.test.tsx

@@ -299,12 +299,56 @@ describe('Legend', () => {
       expect(screen.getByText('Custom Title')).toBeInTheDocument();
     });
 
-    it('does not render when startSize equals endSize', () => {
-      const { container } = renderLegend({
-        sizeLegend: { ...sizeLegend, startSize: 20, endSize: 20 },
+    it('renders single-value fallback when startSize equals endSize', () => {
+      renderLegend({
+        sizeLegend: {
+          ...sizeLegend,
+          startSize: 20,
+          endSize: 20,
+          legendName: 'Sensor A',
+        },
         categories: {},
       });
-      expect(container).toBeEmptyDOMElement();
+      // Should show the legend title and the legend name instead of graduated icons
+      expect(screen.getByText('Population')).toBeInTheDocument();
+      expect(screen.getByText('Sensor A')).toBeInTheDocument();
+      expect(screen.queryByTestId('graduated-icons')).not.toBeInTheDocument();
+    });
+
+    it('single-value fallback uses singleValueColor for swatch when provided', () => {
+      renderLegend({
+        sizeLegend: {
+          ...sizeLegend,
+          startSize: 20,
+          endSize: 20,
+          legendName: 'Sensor A',
+          singleValueColor: [255, 128, 0, 255] as [
+            number,
+            number,
+            number,
+            number,
+          ],
+        },
+        categories: {},
+      });
+      // The swatch should be present and graduated icons absent
+      expect(screen.getByText('Sensor A')).toBeInTheDocument();
+      expect(screen.queryByTestId('graduated-icons')).not.toBeInTheDocument();
+    });
+
+    it('single-value fallback falls back to fillColor when no singleValueColor', () => {
+      renderLegend({
+        sizeLegend: {
+          ...sizeLegend,
+          startSize: 20,
+          endSize: 20,
+          legendName: 'Sensor A',
+        },
+        fillColor: [0, 200, 100, 255] as [number, number, number, number],
+        categories: {},
+      });
+      expect(screen.getByText('Sensor A')).toBeInTheDocument();
+      expect(screen.queryByTestId('graduated-icons')).not.toBeInTheDocument();
     });
 
     it('passes bounds to GraduatedIcons', () => {
@@ -373,6 +417,41 @@ describe('Legend', () => {
       expect(container.querySelector('.gradient-bar')).not.toBeInTheDocument();
     });
 
+    it('renders single-value fallback when combined and startSize equals endSize', () => {
+      renderLegend({
+        isCombinedMetricSize: true,
+        metricLegend,
+        sizeLegend: {
+          ...sizeLegend,
+          startSize: 20,
+          endSize: 20,
+          legendName: 'Single Sensor',
+        },
+        categories: {},
+      });
+      expect(screen.getByText('Single Sensor')).toBeInTheDocument();
+      expect(screen.queryByTestId('graduated-icons')).not.toBeInTheDocument();
+      // Should not render the gradient bar either (combined mode suppresses it)
+      const { container } = renderLegend({
+        isCombinedMetricSize: true,
+        metricLegend,
+        sizeLegend: {
+          ...sizeLegend,
+          startSize: 20,
+          endSize: 20,
+          legendName: 'Single Sensor',
+          singleValueColor: [200, 50, 50, 255] as [
+            number,
+            number,
+            number,
+            number,
+          ],
+        },
+        categories: {},
+      });
+      expect(container.querySelector('.gradient-bar')).not.toBeInTheDocument();
+    });
+
     it('still renders categories alongside combined legend', () => {
       renderLegend({
         isCombinedMetricSize: true,