Small improvement for readability

src/platform/packages/shared/kbn-esql-utils/src/utils/cascaded_documents_helpers/index.ts

@@ -30,6 +30,7 @@ import type {
   ESQLBinaryExpression,
   ESQLUnaryExpression,
   ESQLPostfixUnaryExpression,
+  ESQLProperNode,
 } from '@kbn/esql-language/src/types';
 import type { DataView } from '@kbn/data-views-plugin/public';
 import type { ESQLControlVariable } from '@kbn/esql-types';
@@ -54,6 +55,22 @@ import {
   isCategorizeFunctionWithFunctionArgument,
 } from './utils';
 
+const hasUnsupportedGroupingFunction = (definition: ESQLProperNode): boolean => {
+  const funcExpr = isFunctionExpression(definition)
+    ? definition
+    : isInlineCast(definition) && isFunctionExpression(definition.value)
+    ? definition.value
+    : null;
+
+  if (!funcExpr) {
+    return false;
+  }
+
+  return (
+    !isSupportedStatsFunction(funcExpr.name) || isCategorizeFunctionWithFunctionArgument(funcExpr)
+  );
+};
+
 type NodeType = 'group' | 'leaf';
 
 export interface AppliedStatsFunction {
@@ -143,14 +160,7 @@ export const getESQLStatsQueryMeta = (queryString: string): ESQLStatsQueryMeta =
 
     const groupFieldDefinition = getFieldDefinitionFromArg(groupFieldNode.arg);
 
-    if (
-      (isFunctionExpression(groupFieldDefinition) &&
-        (!isSupportedStatsFunction(groupFieldDefinition.name) ||
-          isCategorizeFunctionWithFunctionArgument(groupFieldDefinition))) ||
-      (isInlineCast(groupFieldDefinition) &&
-        isFunctionExpression(groupFieldDefinition.value) &&
-        !isSupportedStatsFunction(groupFieldDefinition.value.name))
-    ) {
+    if (hasUnsupportedGroupingFunction(groupFieldDefinition)) {
       // if the group field has a grouping function that is not supported,
       // this nullifies the entire query to count as a valid query for the cascade experience
       groupByFields.splice(0, groupByFields.length);