unlocks aggregation suggestions in STATS autocomplete

Author: momovdg

src/platform/packages/shared/kbn-esql-language/src/commands/registry/stats/autocomplete.test.ts

@@ -420,6 +420,28 @@ describe('STATS Autocomplete', () => {
         await statsExpectSuggestions('from a | stats a=min(b), b=max(', expected, mockCallbacks);
       });
 
+      test('inside a function arg with hint.kind === "aggregation" (e.g. SPARKLINE first arg), only aggregation functions are suggested', async () => {
+        // Mock fields just to verify the resolver's exclusive path skips the composite (fields) branch
+        const allFields = getFieldNamesByType('any');
+        (mockCallbacks.getByType as jest.Mock).mockResolvedValue(
+          allFields.map((name) => ({ label: name, text: name }))
+        );
+
+        const expectedAggregations = getFunctionSignaturesByReturnType(
+          Location.STATS,
+          ['integer', 'long', 'double'],
+          { agg: true, timeseriesAgg: true },
+          undefined,
+          ['sparkline']
+        ).map((s) => `${s},`);
+
+        await statsExpectSuggestions(
+          'from a | stats SPARKLINE(',
+          expectedAggregations,
+          mockCallbacks
+        );
+      });
+
       test('inside function argument list', async () => {
         const expectedFieldsAvg = getFieldNamesByType(AVG_TYPES);
         (mockCallbacks.getByType as jest.Mock).mockResolvedValue(

src/platform/packages/shared/kbn-esql-language/src/commands/registry/stats/autocomplete.ts

@@ -416,14 +416,30 @@ function buildCustomFilteringContext(
 
   if (!isInBy) {
     statsSpecificFunctionsToIgnore.push(
-      ...getFunctionsToIgnoreForStats(command, finalCommandArgIndex),
-      ...(isAggFunctionUsedAlready(command, finalCommandArgIndex)
-        ? getAllFunctions({ type: FunctionDefinitionTypes.AGG }).map(({ name }) => name)
-        : []),
-      ...(isTimeseriesAggUsedAlready(command, finalCommandArgIndex)
-        ? getAllFunctions({ type: FunctionDefinitionTypes.TIME_SERIES_AGG }).map(({ name }) => name)
-        : [])
+      ...getFunctionsToIgnoreForStats(command, finalCommandArgIndex)
     );
+
+    // The "no nested aggregations" rule applies unless the cursor's param
+    // explicitly expects an aggregation (e.g. SPARKLINE's first arg has
+    // hint.kind === 'aggregation'), in which case nesting is required, not forbidden.
+    const expectsAggregation = basicContext.paramDefinitions.some(
+      (p) => p.hint?.kind === 'aggregation'
+    );
+
+    if (!expectsAggregation) {
+      if (isAggFunctionUsedAlready(command, finalCommandArgIndex)) {
+        statsSpecificFunctionsToIgnore.push(
+          ...getAllFunctions({ type: FunctionDefinitionTypes.AGG }).map(({ name }) => name)
+        );
+      }
+      if (isTimeseriesAggUsedAlready(command, finalCommandArgIndex)) {
+        statsSpecificFunctionsToIgnore.push(
+          ...getAllFunctions({ type: FunctionDefinitionTypes.TIME_SERIES_AGG }).map(
+            ({ name }) => name
+          )
+        );
+      }
+    }
   }
 
   return {