fix: Improve conditional rendering in ChartWidget (#36806)

## Description
Simplify the conditional rendering logic in the ChartWidget component by
separating the cases for an empty chart and loading state. This improves
readability and maintainability of the code.


Fixes #36213
_or_  
Fixes `Issue URL`
> [!WARNING]  
> _If no issue exists, please create an issue first, and check with the
maintainers if the issue is valid._

## Automation

/ok-to-test tags="@tag.Chart"

### 🔍 Cypress test results
<!-- This is an auto-generated comment: Cypress test results  -->
> [!TIP]
> 🟢 🟢 🟢 All cypress tests have passed! 🎉 🎉 🎉
> Workflow run:
<https://github.com/appsmithorg/appsmith/actions/runs/11288506543>
> Commit: 09b7635c04bbf72b12a6461deafc0789f7a04ea7
> <a
href="https://internal.appsmith.com/app/cypress-dashboard/rundetails-65890b3c81d7400d08fa9ee5?branch=master&workflowId=11288506543&attempt=1"
target="_blank">Cypress dashboard</a>.
> Tags: `@tag.Chart`
> Spec:
> <hr>Fri, 11 Oct 2024 08:17:45 UTC
<!-- end of auto-generated comment: Cypress test results  -->


## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [x] No


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Enhanced the `ChartWidget` component for improved control flow and
readability.
- Introduced a streamlined rendering process for different chart states
(loading, empty, error).
- Added an optional `onDataPointClick` property to the
`ChartWidgetProps` interface.

- **Improvements**
	- Modularized rendering logic for better maintainability.
- Added a comprehensive set of unit tests for the `ChartWidget`
component to ensure consistent rendering behavior across various states.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

app/client/src/widgets/ChartWidget/widget/ChartsRendered.test.tsx

@@ -0,0 +1,125 @@
+import { RenderModes } from "constants/WidgetConstants";
+import ChartWidget, { type ChartWidgetProps } from ".";
+import { LabelOrientation, type ChartData } from "../constants";
+import { EmptyChartData } from "../component/EmptyChartData";
+import type { WidgetError } from "widgets/BaseWidget";
+
+describe("ChartWidget getWidgetView", () => {
+  let chartWidget: ChartWidget;
+
+  const seriesData1: ChartData = {
+    seriesName: "series1",
+    data: [{ x: "x1", y: 1 }],
+    color: "series1color",
+  };
+  const seriesData2: ChartData = {
+    seriesName: "series2",
+    data: [{ x: "x1", y: 2 }],
+    color: "series2color",
+  };
+  const defaultProps: ChartWidgetProps = {
+    allowScroll: true,
+    showDataPointLabel: true,
+    chartData: {
+      seriesID1: seriesData1,
+      seriesID2: seriesData2,
+    },
+    chartName: "chart name",
+    type: "CHART_WIDGET",
+    chartType: "AREA_CHART",
+    customEChartConfig: {},
+    customFusionChartConfig: { type: "type", dataSource: undefined },
+    hasOnDataPointClick: true,
+    isVisible: true,
+    isLoading: false,
+    setAdaptiveYMin: false,
+    labelOrientation: LabelOrientation.AUTO,
+    onDataPointClick: "",
+    widgetId: "widgetID",
+    xAxisName: "xaxisname",
+    yAxisName: "yaxisname",
+    borderRadius: "1",
+    boxShadow: "1",
+    primaryColor: "primarycolor",
+    fontFamily: "fontfamily",
+    dimensions: { componentWidth: 11, componentHeight: 11 },
+    parentColumnSpace: 1,
+    parentRowSpace: 1,
+    topRow: 0,
+    bottomRow: 0,
+    leftColumn: 0,
+    rightColumn: 0,
+    widgetName: "widgetName",
+    version: 1,
+    renderMode: RenderModes.CANVAS,
+  };
+  const errors: WidgetError[] = [
+    {
+      name: "error",
+      type: "configuration",
+      message: "We have a error",
+    },
+  ];
+
+  describe("loading state", () => {
+    it("isLoading: true", () => {
+      chartWidget = new ChartWidget({ ...defaultProps, isLoading: true });
+
+      const view = chartWidget.getWidgetView();
+
+      expect(view.props.children.props.isLoading).toBe(true);
+    });
+
+    it("isLoading: true + errors", () => {
+      chartWidget = new ChartWidget({
+        ...defaultProps,
+        isLoading: true,
+        errors,
+      });
+
+      const view = chartWidget.getWidgetView();
+
+      expect(view.props.children.props.isLoading).toBe(true);
+    });
+    it("isLoading: true + emptyChartData", () => {
+      chartWidget = new ChartWidget({
+        ...defaultProps,
+        isLoading: true,
+        chartData: {},
+      });
+
+      const view = chartWidget.getWidgetView();
+
+      expect(view.props.children.props.isLoading).toBe(true);
+    });
+  });
+
+  it("renders error state", () => {
+    chartWidget = new ChartWidget({
+      ...defaultProps,
+      errors,
+    });
+
+    const view = chartWidget.getWidgetView();
+
+    expect(view.props.error.message).toBe("We have a error");
+  });
+
+  it("renders empty chart data state", () => {
+    chartWidget = new ChartWidget({ ...defaultProps, chartData: {} });
+
+    const view = chartWidget.getWidgetView();
+
+    expect(view.type).toEqual(EmptyChartData);
+  });
+
+  it("renders chart with data", () => {
+    chartWidget = new ChartWidget(defaultProps);
+    const view = chartWidget.getWidgetView();
+
+    expect(view.props.children.props.chartData).toEqual({
+      seriesID1: seriesData1,
+      seriesID2: seriesData2,
+    });
+  });
+});

app/client/src/widgets/ChartWidget/widget/index.tsx

@@ -226,42 +226,50 @@ class ChartWidget extends BaseWidget<ChartWidgetProps, WidgetState> {
   getWidgetView() {
     const errors = syntaxErrorsFromProps(this.props);
 
-    if (errors.length == 0) {
-      if (emptyChartData(this.props)) {
-        return <EmptyChartData />;
-      } else {
-        return (
-          <Suspense fallback={<Skeleton />}>
-            <ChartComponent
-              allowScroll={this.props.allowScroll}
-              borderRadius={this.props.borderRadius}
-              boxShadow={this.props.boxShadow}
-              chartData={this.props.chartData}
-              chartName={this.props.chartName}
-              chartType={this.props.chartType}
-              customEChartConfig={this.props.customEChartConfig}
-              customFusionChartConfig={this.props.customFusionChartConfig}
-              dimensions={this.props}
-              fontFamily={ChartWidget.fontFamily}
-              hasOnDataPointClick={Boolean(this.props.onDataPointClick)}
-              isLoading={this.props.isLoading}
-              isVisible={this.props.isVisible}
-              key={this.props.widgetId}
-              labelOrientation={this.props.labelOrientation}
-              onDataPointClick={this.onDataPointClick}
-              primaryColor={this.props.accentColor ?? Colors.ROYAL_BLUE_2}
-              setAdaptiveYMin={this.props.setAdaptiveYMin}
-              showDataPointLabel={this.props.showDataPointLabel}
-              widgetId={this.props.widgetId}
-              xAxisName={this.props.xAxisName}
-              yAxisName={this.props.yAxisName}
-            />
-          </Suspense>
-        );
-      }
-    } else {
+    if (this.props.isLoading) {
+      return this.renderChartWithData();
+    }
+
+    if (errors.length > 0) {
       return <ChartErrorComponent error={errors[0]} />;
     }
+
+    if (emptyChartData(this.props)) {
+      return <EmptyChartData />;
+    }
+
+    return this.renderChartWithData();
+  }
+
+  renderChartWithData() {
+    return (
+      <Suspense fallback={<Skeleton />}>
+        <ChartComponent
+          allowScroll={this.props.allowScroll}
+          borderRadius={this.props.borderRadius}
+          boxShadow={this.props.boxShadow}
+          chartData={this.props.chartData}
+          chartName={this.props.chartName}
+          chartType={this.props.chartType}
+          customEChartConfig={this.props.customEChartConfig}
+          customFusionChartConfig={this.props.customFusionChartConfig}
+          dimensions={this.props}
+          fontFamily={ChartWidget.fontFamily}
+          hasOnDataPointClick={Boolean(this.props.onDataPointClick)}
+          isLoading={this.props.isLoading}
+          isVisible={this.props.isVisible}
+          key={this.props.widgetId}
+          labelOrientation={this.props.labelOrientation}
+          onDataPointClick={this.onDataPointClick}
+          primaryColor={this.props.accentColor ?? Colors.ROYAL_BLUE_2}
+          setAdaptiveYMin={this.props.setAdaptiveYMin}
+          showDataPointLabel={this.props.showDataPointLabel}
+          widgetId={this.props.widgetId}
+          xAxisName={this.props.xAxisName}
+          yAxisName={this.props.yAxisName}
+        />
+      </Suspense>
+    );
   }
 }