private/date: fix PeriodToTime for invalid periods

Updates #6818

Change-Id: I626945636bac901700b900a5594473fa33c3f288

private/date/utils.go

@@ -4,7 +4,10 @@
 // Package date contains various date-related utilities
 package date
 
-import "time"
+import (
+	"fmt"
+	"time"
+)
 
 // MonthBoundary extract month from the provided date and returns its edges.
 func MonthBoundary(t time.Time) (time.Time, time.Time) {
@@ -21,8 +24,11 @@ func DayBoundary(t time.Time) (time.Time, time.Time) {
 
 // PeriodToTime returns time.Time period in format YYYY-MM from string.
 func PeriodToTime(period string) (_ time.Time, err error) {
+	if len(period) < 7 {
+		return time.Time{}, fmt.Errorf("invalid period %q", period)
+	}
+	shortPeriod := period[:7]
 	layout := "2006-01"
-	shortPeriod := period[0:7]
 	result, err := time.Parse(layout, shortPeriod)
 	if err != nil {
 		return time.Time{}, err

private/date/utils_test.go

@@ -48,6 +48,21 @@ func TestPeriodToTime(t *testing.T) {
 	}
 }
 
+func TestPeriodToTime_Invalid(t *testing.T) {
+	testCases := [...]struct {
+		period string
+		error  string
+	}{
+		{"", "invalid period \"\""},
+		{"2020", "invalid period \"2020\""},
+	}
+
+	for _, tc := range testCases {
+		_, err := date.PeriodToTime(tc.period)
+		require.ErrorContains(t, err, tc.error)
+	}
+}
+
 func TestMonthsBetweenDates(t *testing.T) {
 	testCases := [...]struct {
 		from         time.Time