promql: fix parsing ambiguity for serial repetitions

promql/lex.go

@@ -666,7 +666,8 @@ func lexNumberOrDuration(l *lexer) stateFn {
 // not necessarily a valid number. This case is caught by the parser.
 func (l *lexer) scanNumber() bool {
 	digits := "0123456789"
-	if l.accept("0") && l.accept("xX") {
+	// Disallow hexal in series descriptions as the syntax is ambiguous.
+	if !l.seriesDesc && l.accept("0") && l.accept("xX") {
 		digits = "0123456789abcdefABCDEF"
 	}
 	l.acceptRun(digits)
@@ -677,12 +678,13 @@ func (l *lexer) scanNumber() bool {
 		l.accept("+-")
 		l.acceptRun("0123456789")
 	}
-	// Next thing must not be alphanumeric.
-	if isAlphaNumeric(l.peek()) && !l.seriesDesc {
-		return false
-	}
+	// Next thing must not be alphanumeric unless it's the times token
+	// for series repetitions.
+	if r := l.peek(); (l.seriesDesc && r == 'x') || !isAlphaNumeric(r) {
 		return true
 	}
+	return false
+}
 
 // lexIdentifier scans an alphanumeric identifier. The next character
 // is known to be a letter.

promql/parse_test.go

@@ -1274,6 +1274,13 @@ var testSeries = []struct {
 			"a": "b",
 		},
 		expectedValues: newSeq(1, 2, 3, -7, -17, -27, -37),
+	}, {
+		input: `my_metric{a="b"} 1 2 3-0x4`,
+		expectedMetric: clientmodel.Metric{
+			clientmodel.MetricNameLabel: "my_metric",
+			"a": "b",
+		},
+		expectedValues: newSeq(1, 2, 3, 3, 3, 3, 3),
 	}, {
 		input: `my_metric{a="b"} 1 3 _ 5 _x4`,
 		expectedMetric: clientmodel.Metric{