Fix InfluxDB tag variables parsing (#46862)

* regex bug fixed

* remove unnecessary test

pkg/tsdb/influxdb/response_parser.go

@@ -16,7 +16,7 @@ import (
 type ResponseParser struct{}
 
 var (
-	legendFormat = regexp.MustCompile(`\[\[([\@\/\w-]+)(\.[\@\/\w-]+)*\]\]*|\$(\s*([\@\w-]+?))*`)
+	legendFormat = regexp.MustCompile(`\[\[([\@\/\w-]+)(\.[\@\/\w-]+)*\]\]*|\$([\@\w-]+?)*`)
 )
 
 func (rp *ResponseParser) Parse(buf io.ReadCloser, queries []Query) *backend.QueryDataResponse {

pkg/tsdb/influxdb/response_parser_test.go

@@ -492,6 +492,16 @@ func TestInfluxdbResponseParser(t *testing.T) {
 				t.Errorf("Result mismatch (-want +got):\n%s", diff)
 			}
 
+			query = &Query{Alias: "alias $0, $1 - $2 - $3, $4: something"}
+			result = parser.Parse(prepare(response), addQueryToQueries(*query))
+			frame = result.Responses["A"]
+			name = "alias cpu, upc - $2 - $3, $4: something"
+			testFrame.Name = name
+			testFrame.Fields[1].Config.DisplayNameFromDS = name
+			if diff := cmp.Diff(testFrame, frame.Frames[0], data.FrameTestCompareOptions()...); diff != "" {
+				t.Errorf("Result mismatch (-want +got):\n%s", diff)
+			}
+
 			query = &Query{Alias: "alias $1"}
 			result = parser.Parse(prepare(response), addQueryToQueries(*query))
 			frame = result.Responses["A"]