fix(plugin-chart-echarts): guard loadLocale on the time section, dispose test chart

Review feedback: the keys-length guard was weaker than the crash
invariant. The failure mode is echarts' time formatter reading
time.month from a locale registered without a time section, so check
for that section directly; a partial bundle now falls back to the
builtin locale too. Also dispose the SSR chart instance the rendering
test creates so it doesn't leak across the jest worker.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: claude

superset-frontend/plugins/plugin-chart-echarts/src/components/echartsLocale.ts

@@ -94,7 +94,11 @@ export const loadLocale = async (
     // Depending on the module system, the locale object is either the
     // module's default export or the module namespace itself.
     const localeObj = mod.default ?? (mod as unknown as EChartsLocaleOption);
-    if (localeObj && Object.keys(localeObj).length > 0) {
+    // registerLocale replaces any builtin entry under the same key, and
+    // `time` is the section whose absence crashes every time-axis chart, so
+    // a locale without it (an empty or partial bundle) must not be
+    // registered. Fall back to the builtin locale instead.
+    if (localeObj?.time) {
       return localeObj;
     }
   } catch {

superset-frontend/plugins/plugin-chart-echarts/test/components/echartsLocale.test.ts

@@ -57,22 +57,26 @@ test('registering the loaded EN locale keeps time-axis charts rendering', async
     height: 300,
     locale: 'EN',
   });
-  chart.setOption(
-    {
-      xAxis: { type: 'time' },
-      yAxis: { type: 'value' },
-      series: [
-        {
-          type: 'line',
-          data: [
-            [new Date(1965, 0, 1).getTime(), 100],
-            [new Date(1985, 0, 1).getTime(), 200],
-            [new Date(2005, 0, 1).getTime(), 150],
-          ],
-        },
-      ],
-    },
-    { notMerge: true, lazyUpdate: false },
-  );
-  expect(chart.renderToSVGString()).toContain('<svg');
+  try {
+    chart.setOption(
+      {
+        xAxis: { type: 'time' },
+        yAxis: { type: 'value' },
+        series: [
+          {
+            type: 'line',
+            data: [
+              [new Date(1965, 0, 1).getTime(), 100],
+              [new Date(1985, 0, 1).getTime(), 200],
+              [new Date(2005, 0, 1).getTime(), 150],
+            ],
+          },
+        ],
+      },
+      { notMerge: true, lazyUpdate: false },
+    );
+    expect(chart.renderToSVGString()).toContain('<svg');
+  } finally {
+    chart.dispose();
+  }
 });