feat: legend auto generation based on group by (#10529)

* feat: legend auto generation based on group by

* chore: removed redundent check from util

Author: ahrefabhi

frontend/src/components/QueryBuilderV2/QueryV2/QueryAddOns/QueryAddOns.tsx

@@ -14,6 +14,7 @@ import { MetricAggregation } from 'types/api/v5/queryRange';
 import { DataSource, ReduceOperators } from 'types/common/queryBuilder';
 
 import HavingFilter from './HavingFilter/HavingFilter';
+import { buildDefaultLegendFromGroupBy } from './utils';
 
 import './QueryAddOns.styles.scss';
 
@@ -250,12 +251,33 @@ function QueryAddOns({
 	}, [panelType, isListViewPanel, query, showReduceTo]);
 
 	const handleOptionClick = (e: RadioChangeEvent): void => {
-		if (selectedViews.find((view) => view.key === e.target.value.key)) {
-			setSelectedViews(
-				selectedViews.filter((view) => view.key !== e.target.value.key),
+		const clickedAddOn = e.target.value as AddOn;
+		const isAlreadySelected = selectedViews.some(
+			(view) => view.key === clickedAddOn.key,
+		);
+
+		if (isAlreadySelected) {
+			setSelectedViews((prev) =>
+				prev.filter((view) => view.key !== clickedAddOn.key),
 			);
 		} else {
-			setSelectedViews([...selectedViews, e.target.value]);
+			// When enabling Legend format for the first time with an empty legend
+			// and existing group-by keys, prefill the legend using all group-by keys.
+			// This keeps existing custom legends intact and only helps seed a sensible default.
+			if (
+				clickedAddOn.key === ADD_ONS_KEYS.LEGEND_FORMAT &&
+				isEmpty(query?.legend) &&
+				Array.isArray(query.groupBy) &&
+				query.groupBy.length > 0
+			) {
+				const defaultLegend = buildDefaultLegendFromGroupBy(query.groupBy);
+
+				if (defaultLegend) {
+					handleChangeQueryLegend(defaultLegend);
+				}
+			}
+
+			setSelectedViews((prev) => [...prev, clickedAddOn]);
 		}
 	};
 
@@ -288,12 +310,9 @@ function QueryAddOns({
 		[handleSetQueryData, index, query],
 	);
 
-	const handleRemoveView = useCallback(
-		(key: string): void => {
-			setSelectedViews(selectedViews.filter((view) => view.key !== key));
-		},
-		[selectedViews],
-	);
+	const handleRemoveView = useCallback((key: string): void => {
+		setSelectedViews((prev) => prev.filter((view) => view.key !== key));
+	}, []);
 
 	const handleChangeQueryLegend = useCallback(
 		(value: string) => {
@@ -379,8 +398,8 @@ function QueryAddOns({
 								<div className="input">
 									<HavingFilter
 										onClose={(): void => {
-											setSelectedViews(
-												selectedViews.filter((view) => view.key !== 'having'),
+											setSelectedViews((prev) =>
+												prev.filter((view) => view.key !== 'having'),
 											);
 										}}
 										onChange={handleChangeHaving}
@@ -399,7 +418,9 @@ function QueryAddOns({
 								initialValue={query?.limit ?? undefined}
 								placeholder="Enter limit"
 								onClose={(): void => {
-									setSelectedViews(selectedViews.filter((view) => view.key !== 'limit'));
+									setSelectedViews((prev) =>
+										prev.filter((view) => view.key !== 'limit'),
+									);
 								}}
 								closeIcon={<ChevronUp size={16} />}
 							/>
@@ -482,8 +503,8 @@ function QueryAddOns({
 								onChange={handleChangeQueryLegend}
 								initialValue={isEmpty(query?.legend) ? undefined : query?.legend}
 								onClose={(): void => {
-									setSelectedViews(
-										selectedViews.filter((view) => view.key !== 'legend_format'),
+									setSelectedViews((prev) =>
+										prev.filter((view) => view.key !== 'legend_format'),
 									);
 								}}
 								closeIcon={<ChevronUp size={16} />}

frontend/src/components/QueryBuilderV2/QueryV2/QueryAddOns/utils.ts

@@ -0,0 +1,16 @@
+import { IBuilderQuery } from 'types/api/queryBuilder/queryBuilderData';
+
+export const buildDefaultLegendFromGroupBy = (
+	groupBy: IBuilderQuery['groupBy'],
+): string | null => {
+	const segments = groupBy
+		.map((item) => item?.key)
+		.filter((key): key is string => Boolean(key))
+		.map((key) => `${key} = {{${key}}}`);
+
+	if (segments.length === 0) {
+		return null;
+	}
+
+	return segments.join(', ');
+};

frontend/src/components/QueryBuilderV2/__tests__/QueryAddOns.test.tsx

@@ -275,4 +275,59 @@ describe('QueryAddOns', () => {
 			});
 		});
 	});
+
+	it('auto-generates legend from all groupBy keys when enabling Legend format with empty legend', async () => {
+		const user = userEvent.setup();
+		const query = baseQuery({
+			groupBy: [{ key: 'service.name' }, { key: 'operation' }],
+		});
+
+		render(
+			<QueryAddOns
+				query={query}
+				version="v5"
+				isListViewPanel={false}
+				showReduceTo={false}
+				panelType={PANEL_TYPES.TIME_SERIES}
+				index={0}
+				isForTraceOperator={false}
+			/>,
+		);
+
+		const legendTab = screen.getByTestId('query-add-on-legend_format');
+		await user.click(legendTab);
+
+		expect(mockHandleChangeQueryData).toHaveBeenCalledWith(
+			'legend',
+			'service.name = {{service.name}}, operation = {{operation}}',
+		);
+	});
+
+	it('does not override existing legend when enabling Legend format', async () => {
+		const user = userEvent.setup();
+		const query = baseQuery({
+			legend: 'existing legend',
+			groupBy: [{ key: 'service.name' }],
+		});
+
+		render(
+			<QueryAddOns
+				query={query}
+				version="v5"
+				isListViewPanel={false}
+				showReduceTo={false}
+				panelType={PANEL_TYPES.TIME_SERIES}
+				index={0}
+				isForTraceOperator={false}
+			/>,
+		);
+
+		const legendTab = screen.getByTestId('query-add-on-legend_format');
+		await user.click(legendTab);
+
+		expect(mockHandleChangeQueryData).not.toHaveBeenCalledWith(
+			'legend',
+			expect.anything(),
+		);
+	});
 });