Label name check for 'count_values' (#4585)

Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>

promql/engine.go

@@ -29,6 +29,7 @@ import (
 	"github.com/go-kit/kit/log/level"
 	opentracing "github.com/opentracing/opentracing-go"
 	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/pkg/timestamp"
 	"github.com/prometheus/prometheus/pkg/value"
@@ -1494,6 +1495,9 @@ func (ev *evaluator) aggregation(op ItemType, grouping []string, without bool, p
 	var valueLabel string
 	if op == itemCountValues {
 		valueLabel = param.(string)
+		if !model.LabelName(valueLabel).IsValid() {
+			ev.errorf("invalid label name %q", valueLabel)
+		}
 		if !without {
 			grouping = append(grouping, valueLabel)
 		}

promql/engine_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/go-kit/kit/log"
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/storage"
+	"github.com/prometheus/prometheus/util/testutil"
 )
 
 func TestQueryConcurrency(t *testing.T) {
@@ -272,6 +273,7 @@ load 10s
 		Start       time.Time
 		End         time.Time
 		Interval    time.Duration
+		ShouldError bool
 	}{
 		// Instant queries.
 		{
@@ -326,6 +328,10 @@ load 10s
 			End:      time.Unix(10, 0),
 			Interval: 5 * time.Second,
 		},
+		{
+			Query:       `count_values("wrong label!", metric)`,
+			ShouldError: true,
+		},
 	}
 
 	for _, c := range cases {
@@ -340,6 +346,10 @@ load 10s
 			t.Fatalf("unexpected error creating query: %q", err)
 		}
 		res := qry.Exec(test.Context())
+		if c.ShouldError {
+			testutil.NotOk(t, res.Err, "expected error for the query %q", c.Query)
+			continue
+		}
 		if res.Err != nil {
 			t.Fatalf("unexpected error running query: %q", res.Err)
 		}