fix(echarts): suppress phantom x-axis label at axis edge when no time grain (#39972)

superset-frontend/plugins/plugin-chart-echarts/src/MixedTimeseries/transformProps.ts

@@ -589,7 +589,8 @@ export default function transformProps(
       ? getXAxisFormatter(xAxisTimeFormat, timeGrainSqla)
       : String;
 
-  const showMaxLabel = xAxisType === AxisType.Time && xAxisLabelRotation === 0;
+  const showMaxLabel =
+    xAxisType === AxisType.Time && xAxisLabelRotation === 0 && !!timeGrainSqla;
   const deduplicatedFormatter = showMaxLabel
     ? (() => {
         let lastLabel: string | undefined;

superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformProps.ts

@@ -861,7 +861,8 @@ export default function transformProps(
   // boundary that formats identically to the last data-point tick (e.g.
   // "2005" appears twice with Year grain). Wrap the formatter to suppress
   // consecutive duplicate labels.
-  const showMaxLabel = xAxisType === AxisType.Time && xAxisLabelRotation === 0;
+  const showMaxLabel =
+    xAxisType === AxisType.Time && xAxisLabelRotation === 0 && !!timeGrainSqla;
   const deduplicatedFormatter = showMaxLabel
     ? (() => {
         let lastLabel: string | undefined;

superset-frontend/plugins/plugin-chart-echarts/test/Timeseries/transformProps.test.ts

@@ -1444,7 +1444,7 @@ test('x-axis formatter deduplicates consecutive identical labels for coarse time
   const chartProps = createTestChartProps({
     formData: {
       granularity_sqla: 'ds',
-      time_grain_sqla: TimeGranularity.YEAR,
+      timeGrainSqla: TimeGranularity.YEAR,
       xAxisTimeFormat: '%Y',
     },
     queriesData: [
@@ -1473,6 +1473,30 @@ test('x-axis formatter deduplicates consecutive identical labels for coarse time
   expect(label4).toBe('');
 });
 
+test('x-axis does not force showMaxLabel when no time grain is set', () => {
+  const data = [
+    { __timestamp: Date.UTC(2003, 0, 6), sales: 100 },
+    { __timestamp: Date.UTC(2004, 5, 15), sales: 200 },
+    { __timestamp: Date.UTC(2005, 4, 31), sales: 300 },
+  ];
+
+  const chartProps = createTestChartProps({
+    formData: {
+      granularity_sqla: 'ds',
+      timeGrainSqla: undefined,
+    },
+    queriesData: [
+      createTestQueryData(data, {
+        colnames: ['__timestamp', 'sales'],
+        coltypes: [GenericDataType.Temporal, GenericDataType.Numeric],
+      }),
+    ],
+  });
+
+  const xAxisResult = transformProps(chartProps).echartOptions.xAxis as any;
+  expect(xAxisResult.axisLabel.showMaxLabel).not.toBe(true);
+});
+
 test('numeric x coltype routes through the number formatter (not the time formatter)', () => {
   // Regression guard for echarts-timeseries-epoch-x-axis-labels investigation.
   // When the query reports a Numeric x-axis coltype (including epoch-ms-like

superset-frontend/plugins/plugin-chart-echarts/test/Timeseries/transformers.test.ts

@@ -16,7 +16,11 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-import { CategoricalColorScale, ChartProps } from '@superset-ui/core';
+import {
+  CategoricalColorScale,
+  ChartProps,
+  TimeGranularity,
+} from '@superset-ui/core';
 import { GenericDataType } from '@apache-superset/core/common';
 import { supersetTheme } from '@apache-superset/core/theme';
 import type { SeriesOption } from 'echarts';
@@ -235,6 +239,7 @@ function buildTimeseriesChartProps(
       colorScheme: 'bnbColors',
       datasource: '3__table',
       granularity_sqla: 'ds',
+      timeGrainSqla: TimeGranularity.MONTH,
       metric: 'sum__num',
       viz_type: 'my_viz',
       ...overrides,
@@ -263,6 +268,7 @@ test('should configure time axis labels to show max label for last month visibil
     colorScheme: 'bnbColors',
     datasource: '3__table',
     granularity_sqla: 'ds',
+    timeGrainSqla: TimeGranularity.MONTH,
     metric: 'sum__num',
     viz_type: 'my_viz',
   };