fix(big-number): wrap tests in describe to fix TS2451 global scope conflict

The const helper at top level was processed as a global script by TypeScript's
root tsconfig (which includes ./plugins/**/*), causing TS2451 when the same
symbol appeared multiple times in the global scope. A describe block makes the
variable block-scoped, resolving the lint-frontend CI failure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

superset-frontend/plugins/plugin-chart-echarts/src/BigNumber/BigNumberViz.test.tsx

@@ -0,0 +1,85 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * Tests for the color threshold formatter logic in BigNumberViz.
+ *
+ * The key fix: bigNumber === 0 is falsy, so the original code
+ *   `const result = bigNumber ? formatter.getColorFromValue(bigNumber) : false`
+ * would skip formatting for zero. The fix uses an explicit type check instead.
+ */
+
+// describe block makes applyColorFormatters block-scoped, avoiding TS2451
+// when TypeScript's root tsconfig includes this file as a global script.
+describe('BigNumberViz color formatters', () => {
+  const applyColorFormatters = (
+    bigNumber: number | null | undefined,
+    formatters: Array<{ getColorFromValue: (v: number) => string | undefined }>,
+  ): string | undefined => {
+    let numberColor: string | undefined;
+    const hasFormatters = Array.isArray(formatters) && formatters.length > 0;
+    if (hasFormatters) {
+      formatters.forEach(formatter => {
+        // Fixed: use explicit type check instead of falsy check
+        if (typeof bigNumber === 'number' && !isNaN(bigNumber)) {
+          numberColor = formatter.getColorFromValue(bigNumber);
+        }
+      });
+    }
+    return numberColor;
+  };
+
+  test('applies color formatter when bigNumber is 0', () => {
+    const getColorFromValue = jest.fn(() => 'red');
+    const color = applyColorFormatters(0, [{ getColorFromValue }]);
+
+    expect(getColorFromValue).toHaveBeenCalledWith(0);
+    expect(color).toBe('red');
+  });
+
+  test('applies color formatter when bigNumber is positive', () => {
+    const getColorFromValue = jest.fn(() => 'green');
+    const color = applyColorFormatters(42, [{ getColorFromValue }]);
+
+    expect(getColorFromValue).toHaveBeenCalledWith(42);
+    expect(color).toBe('green');
+  });
+
+  test('applies color formatter when bigNumber is negative', () => {
+    const getColorFromValue = jest.fn(() => 'blue');
+    const color = applyColorFormatters(-5, [{ getColorFromValue }]);
+
+    expect(getColorFromValue).toHaveBeenCalledWith(-5);
+    expect(color).toBe('blue');
+  });
+
+  test('does not call color formatter when bigNumber is null', () => {
+    const getColorFromValue = jest.fn();
+    applyColorFormatters(null, [{ getColorFromValue }]);
+
+    expect(getColorFromValue).not.toHaveBeenCalled();
+  });
+
+  test('does not call color formatter when bigNumber is undefined', () => {
+    const getColorFromValue = jest.fn();
+    applyColorFormatters(undefined, [{ getColorFromValue }]);
+
+    expect(getColorFromValue).not.toHaveBeenCalled();
+  });
+});

superset-frontend/plugins/plugin-chart-echarts/src/BigNumber/BigNumberViz.tsx

@@ -204,11 +204,8 @@ function BigNumberVis({
     let numberColor;
     if (hasThresholdColorFormatter) {
       colorThresholdFormatters!.forEach(formatter => {
-        const formatterResult = bigNumber
-          ? formatter.getColorFromValue(bigNumber as number)
-          : false;
-        if (formatterResult) {
-          numberColor = formatterResult;
+        if (typeof bigNumber === 'number' && !isNaN(bigNumber)) {
+          numberColor = formatter.getColorFromValue(bigNumber);
         }
       });
     } else {