lib/promutils, app/vmalert-tool/unittest: move promutils.Duration.ParseTime() to app/vmalert-tool/unittest.durationToTime()

The ParseTime() function looks strange, since it converts relative duration to absolute time since Unix Epoch.
In most scenarios such a conversion is used by mistake.

It is better to do not expose such a function for public use and hide it inside the package where it is needed,
e.g. inside app/vmalert-tool/unittest.

This is a follow-up for dc28196237
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2945
Updates https://github.com/VictoriaMetrics/VictoriaMetrics/pull/4789

app/vmalert-tool/unittest/recording.go

@@ -6,6 +6,7 @@ import (
 	"net/url"
 	"reflect"
 	"sort"
+	"time"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/app/vmalert/datasource"
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/promutils"
@@ -29,7 +30,7 @@ func checkMetricsqlCase(cases []metricsqlTestCase, q datasource.QuerierBuilder)
 	queries := q.BuildWithParams(datasource.QuerierParams{QueryParams: url.Values{"nocache": {"1"}, "latency_offset": {"1ms"}}, DataSourceType: "prometheus"})
 Outer:
 	for _, mt := range cases {
-		result, _, err := queries.Query(context.Background(), mt.Expr, mt.EvalTime.ParseTime())
+		result, _, err := queries.Query(context.Background(), mt.Expr, durationToTime(mt.EvalTime))
 		if err != nil {
 			checkErrs = append(checkErrs, fmt.Errorf("    expr: %q, time: %s, err: %w", mt.Expr,
 				mt.EvalTime.Duration().String(), err))
@@ -90,3 +91,10 @@ Outer:
 	}
 	return
 }
+
+func durationToTime(pd *promutils.Duration) time.Time {
+	if pd == nil {
+		return time.Time{}
+	}
+	return time.UnixMilli(pd.Duration().Milliseconds())
+}

lib/promutils/duration.go

@@ -53,11 +53,3 @@ func ParseDuration(s string) (time.Duration, error) {
 	}
 	return time.Duration(ms) * time.Millisecond, nil
 }
-
-// ParseTime returns time for pd.
-func (pd *Duration) ParseTime() time.Time {
-	if pd == nil {
-		return time.Time{}
-	}
-	return time.UnixMilli(pd.Duration().Milliseconds())
-}