fix(dashboards): Make toPythonString match Python's str() output for null and arrays

- Fix null handling: return 'None' instead of 'null' to match Python's str(None)
- Fix array handling: add spaces after commas, wrap strings in quotes, convert null to 'None' to match Python's str([...])
- Add comprehensive tests for null values and array values with strings, numbers, and null elements

These fixes ensure matchTimeSeriesToTableRow correctly matches table rows with time series groupBy values when null or array values are present, preventing breakdown legend values from showing '—' instead of the correct aggregate.

Author: cursoragent

static/app/views/dashboards/widgetCard/matchTimeSeriesToTableRow.spec.tsx

@@ -90,4 +90,64 @@ describe('matchTimeSeriesToTableRow', () => {
 
     expect(result).toBe(42);
   });
+
+  it('matches null groupBy values correctly', () => {
+    const result = matchTimeSeriesToTableRow({
+      tableDataRows: [
+        {id: '1', project: 'None', 'count()': 15},
+        {id: '2', project: 'my-project', 'count()': 25},
+      ],
+      timeSeries: TimeSeriesFixture({
+        yAxis: 'count()',
+        groupBy: [{key: 'project', value: null}],
+      }),
+    });
+
+    expect(result).toBe(15);
+  });
+
+  it('matches array groupBy values with strings correctly', () => {
+    const result = matchTimeSeriesToTableRow({
+      tableDataRows: [
+        {id: '1', 'error.type': "['ValueError', 'TypeError']", 'count()': 10},
+        {id: '2', 'error.type': "['Exception']", 'count()': 5},
+      ],
+      timeSeries: TimeSeriesFixture({
+        yAxis: 'count()',
+        groupBy: [{key: 'error.type', value: ['ValueError', 'TypeError']}],
+      }),
+    });
+
+    expect(result).toBe(10);
+  });
+
+  it('matches array groupBy values with null elements correctly', () => {
+    const result = matchTimeSeriesToTableRow({
+      tableDataRows: [
+        {id: '1', 'error.type': "['Exception', None, 'TypeError']", 'count()': 20},
+        {id: '2', 'error.type': "['ValueError']", 'count()': 8},
+      ],
+      timeSeries: TimeSeriesFixture({
+        yAxis: 'count()',
+        groupBy: [{key: 'error.type', value: ['Exception', null, 'TypeError']}],
+      }),
+    });
+
+    expect(result).toBe(20);
+  });
+
+  it('matches array groupBy values with numbers correctly', () => {
+    const result = matchTimeSeriesToTableRow({
+      tableDataRows: [
+        {id: '1', 'status_codes': '[200, 404]', 'count()': 30},
+        {id: '2', 'status_codes': '[500]', 'count()': 2},
+      ],
+      timeSeries: TimeSeriesFixture({
+        yAxis: 'count()',
+        groupBy: [{key: 'status_codes', value: [200, 404]}],
+      }),
+    });
+
+    expect(result).toBe(30);
+  });
 });

static/app/views/dashboards/widgetCard/matchTimeSeriestoTableRow.tsx

@@ -7,12 +7,36 @@ import type {TimeSeries} from 'sentry/views/dashboards/widgets/common/types';
  * match that behavior for comparisons.
  */
 function toPythonString(value: unknown): string {
+  if (value === null) {
+    return 'None';
+  }
   if (typeof value === 'boolean') {
     return value ? 'True' : 'False';
   }
   if (Array.isArray(value)) {
-    return `[${value.join(',')}]`;
+    const elements = value.map(item => {
+      if (item === null) {
+        return 'None';
+      }
+      if (typeof item === 'string') {
+        return `'${item}'`;
+      }
+      if (typeof item === 'number') {
+        return item.toString();
+      }
+      // Fallback for unexpected types in array
+      return String(item);
+    });
+    return `[${elements.join(', ')}]`;
+  }
+  if (typeof value === 'string') {
+    return value;
+  }
+  if (typeof value === 'number') {
+    return value.toString();
   }
+  // Fallback for unexpected types (should never be reached with valid GroupBy values)
+  // eslint-disable-next-line @typescript-eslint/no-base-to-string
   return String(value);
 }