tpl/time: Add time.In function

Closes #13548

tpl/time/init.go

@@ -29,7 +29,7 @@ func init() {
 		if d.Conf.Language() == nil {
 			panic("Language must be set")
 		}
-		ctx := New(langs.GetTimeFormatter(d.Conf.Language()), langs.GetLocation(d.Conf.Language()))
+		ctx := New(langs.GetTimeFormatter(d.Conf.Language()), langs.GetLocation(d.Conf.Language()), d)
 
 		ns := &internal.TemplateFuncsNamespace{
 			Name: name,

tpl/time/time.go

@@ -18,16 +18,28 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/gohugoio/hugo/cache/dynacache"
 	"github.com/gohugoio/hugo/common/htime"
+	"github.com/gohugoio/hugo/deps"
 
 	"github.com/spf13/cast"
 )
 
 // New returns a new instance of the time-namespaced template functions.
-func New(timeFormatter htime.TimeFormatter, location *time.Location) *Namespace {
+func New(timeFormatter htime.TimeFormatter, location *time.Location, deps *deps.Deps) *Namespace {
+	if deps.MemCache == nil {
+		panic("must provide MemCache")
+	}
+
 	return &Namespace{
 		timeFormatter: timeFormatter,
 		location:      location,
+		deps:          deps,
+		cacheIn: dynacache.GetOrCreatePartition[string, *time.Location](
+			deps.MemCache,
+			"/tmpl/time/in",
+			dynacache.OptionsPartition{Weight: 30, ClearWhen: dynacache.ClearNever},
+		),
 	}
 }
 
@@ -35,6 +47,8 @@ func New(timeFormatter htime.TimeFormatter, location *time.Location) *Namespace
 type Namespace struct {
 	timeFormatter htime.TimeFormatter
 	location      *time.Location
+	deps          *deps.Deps
+	cacheIn       *dynacache.Partition[string, *time.Location]
 }
 
 // AsTime converts the textual representation of the datetime string into
@@ -71,6 +85,21 @@ func (ns *Namespace) Now() time.Time {
 	return htime.Now()
 }
 
+// In returns the time t in the IANA time zone specified by timeZoneName.
+// If timeZoneName is "" or "UTC", the time is returned in UTC.
+// If timeZoneName is "Local", the time is returned in the system's local time zone.
+// Otherwise, timeZoneName must be a valid IANA location name (e.g., "Europe/Oslo").
+func (ns *Namespace) In(timeZoneName string, t time.Time) (time.Time, error) {
+	location, err := ns.cacheIn.GetOrCreate(dynacache.CleanKey(timeZoneName), func(string) (*time.Location, error) {
+		return time.LoadLocation(timeZoneName)
+	})
+	if err != nil {
+		return time.Time{}, err
+	}
+
+	return t.In(location), nil
+}
+
 // ParseDuration parses the duration string s.
 // A duration string is a possibly signed sequence of
 // decimal numbers, each with optional fraction and a unit suffix,

tpl/time/time_test.go

@@ -11,24 +11,31 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package time
+package time_test
 
 import (
 	"strings"
 	"testing"
-	"time"
+	gtime "time"
 
 	qt "github.com/frankban/quicktest"
 
 	"github.com/gohugoio/hugo/common/htime"
+	"github.com/gohugoio/hugo/hugolib"
+	"github.com/gohugoio/hugo/tpl/time"
+
 	translators "github.com/gohugoio/localescompressed"
 )
 
 func TestTimeLocation(t *testing.T) {
 	t.Parallel()
 
-	loc, _ := time.LoadLocation("America/Antigua")
+	b := hugolib.NewIntegrationTestBuilder(
-	ns := New(htime.NewTimeFormatter(translators.GetTranslator("en")), loc)
+		hugolib.IntegrationTestConfig{T: t},
+	).Build()
+
+	loc, _ := gtime.LoadLocation("America/Antigua")
+	ns := time.New(htime.NewTimeFormatter(translators.GetTranslator("en")), loc, b.H.Deps)
 
 	for i, test := range []struct {
 		name     string
@@ -72,7 +79,7 @@ func TestTimeLocation(t *testing.T) {
 				// See https://github.com/gohugoio/hugo/issues/8843#issuecomment-891551447
 				// Drop the location string (last element) when comparing,
 				// as that may change depending on the local locale.
-				timeStr := result.(time.Time).String()
+				timeStr := result.(gtime.Time).String()
 				timeStr = timeStr[:strings.LastIndex(timeStr, " ")]
 				if !strings.HasPrefix(test.expect.(string), timeStr) {
 					t.Errorf("[%d] AsTime got %v but expected %v", i, timeStr, test.expect)
@@ -85,9 +92,14 @@ func TestTimeLocation(t *testing.T) {
 func TestFormat(t *testing.T) {
 	c := qt.New(t)
 
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{T: t},
+	).Build()
+
 	c.Run("UTC", func(c *qt.C) {
 		c.Parallel()
-		ns := New(htime.NewTimeFormatter(translators.GetTranslator("en")), time.UTC)
+
+		ns := time.New(htime.NewTimeFormatter(translators.GetTranslator("en")), gtime.UTC, b.H.Deps)
 
 		for i, test := range []struct {
 			layout string
@@ -95,15 +107,15 @@ func TestFormat(t *testing.T) {
 			expect any
 		}{
 			{"Monday, Jan 2, 2006", "2015-01-21", "Wednesday, Jan 21, 2015"},
-			{"Monday, Jan 2, 2006", time.Date(2015, time.January, 21, 0, 0, 0, 0, time.UTC), "Wednesday, Jan 21, 2015"},
+			{"Monday, Jan 2, 2006", gtime.Date(2015, gtime.January, 21, 0, 0, 0, 0, gtime.UTC), "Wednesday, Jan 21, 2015"},
 			{"This isn't a date layout string", "2015-01-21", "This isn't a date layout string"},
 			// The following test case gives either "Tuesday, Jan 20, 2015" or "Monday, Jan 19, 2015" depending on the local time zone
-			{"Monday, Jan 2, 2006", 1421733600, time.Unix(1421733600, 0).Format("Monday, Jan 2, 2006")},
+			{"Monday, Jan 2, 2006", 1421733600, gtime.Unix(1421733600, 0).Format("Monday, Jan 2, 2006")},
 			{"Monday, Jan 2, 2006", 1421733600.123, false},
-			{time.RFC3339, time.Date(2016, time.March, 3, 4, 5, 0, 0, time.UTC), "2016-03-03T04:05:00Z"},
+			{gtime.RFC3339, gtime.Date(2016, gtime.March, 3, 4, 5, 0, 0, gtime.UTC), "2016-03-03T04:05:00Z"},
-			{time.RFC1123, time.Date(2016, time.March, 3, 4, 5, 0, 0, time.UTC), "Thu, 03 Mar 2016 04:05:00 UTC"},
+			{gtime.RFC1123, gtime.Date(2016, gtime.March, 3, 4, 5, 0, 0, gtime.UTC), "Thu, 03 Mar 2016 04:05:00 UTC"},
-			{time.RFC3339, "Thu, 03 Mar 2016 04:05:00 UTC", "2016-03-03T04:05:00Z"},
+			{gtime.RFC3339, "Thu, 03 Mar 2016 04:05:00 UTC", "2016-03-03T04:05:00Z"},
-			{time.RFC1123, "2016-03-03T04:05:00Z", "Thu, 03 Mar 2016 04:05:00 UTC"},
+			{gtime.RFC1123, "2016-03-03T04:05:00Z", "Thu, 03 Mar 2016 04:05:00 UTC"},
 			// Custom layouts, as introduced in Hugo 0.87.
 			{":date_medium", "2015-01-21", "Jan 21, 2015"},
 		} {
@@ -128,9 +140,9 @@ func TestFormat(t *testing.T) {
 	c.Run("TZ America/Los_Angeles", func(c *qt.C) {
 		c.Parallel()
 
-		loc, err := time.LoadLocation("America/Los_Angeles")
+		loc, err := gtime.LoadLocation("America/Los_Angeles")
 		c.Assert(err, qt.IsNil)
-		ns := New(htime.NewTimeFormatter(translators.GetTranslator("en")), loc)
+		ns := time.New(htime.NewTimeFormatter(translators.GetTranslator("en")), loc, b.H.Deps)
 
 		d, err := ns.Format(":time_full", "2020-03-09T11:00:00")
 
@@ -142,28 +154,32 @@ func TestFormat(t *testing.T) {
 func TestDuration(t *testing.T) {
 	t.Parallel()
 
-	ns := New(htime.NewTimeFormatter(translators.GetTranslator("en")), time.UTC)
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{T: t},
+	).Build()
+
+	ns := time.New(htime.NewTimeFormatter(translators.GetTranslator("en")), gtime.UTC, b.H.Deps)
 
 	for i, test := range []struct {
 		unit   any
 		num    any
 		expect any
 	}{
-		{"nanosecond", 10, 10 * time.Nanosecond},
+		{"nanosecond", 10, 10 * gtime.Nanosecond},
-		{"ns", 10, 10 * time.Nanosecond},
+		{"ns", 10, 10 * gtime.Nanosecond},
-		{"microsecond", 20, 20 * time.Microsecond},
+		{"microsecond", 20, 20 * gtime.Microsecond},
-		{"us", 20, 20 * time.Microsecond},
+		{"us", 20, 20 * gtime.Microsecond},
-		{"µs", 20, 20 * time.Microsecond},
+		{"µs", 20, 20 * gtime.Microsecond},
-		{"millisecond", 20, 20 * time.Millisecond},
+		{"millisecond", 20, 20 * gtime.Millisecond},
-		{"ms", 20, 20 * time.Millisecond},
+		{"ms", 20, 20 * gtime.Millisecond},
-		{"second", 30, 30 * time.Second},
+		{"second", 30, 30 * gtime.Second},
-		{"s", 30, 30 * time.Second},
+		{"s", 30, 30 * gtime.Second},
-		{"minute", 20, 20 * time.Minute},
+		{"minute", 20, 20 * gtime.Minute},
-		{"m", 20, 20 * time.Minute},
+		{"m", 20, 20 * gtime.Minute},
-		{"hour", 20, 20 * time.Hour},
+		{"hour", 20, 20 * gtime.Hour},
-		{"h", 20, 20 * time.Hour},
+		{"h", 20, 20 * gtime.Hour},
 		{"hours", 20, false},
-		{"hour", "30", 30 * time.Hour},
+		{"hour", "30", 30 * gtime.Hour},
 	} {
 		result, err := ns.Duration(test.unit, test.num)
 		if b, ok := test.expect.(bool); ok && !b {
@@ -181,3 +197,74 @@ func TestDuration(t *testing.T) {
 		}
 	}
 }
+
+func TestIn(t *testing.T) {
+	t.Parallel()
+
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{T: t},
+	).Build()
+
+	ns := time.New(htime.NewTimeFormatter(translators.GetTranslator("en")), gtime.UTC, b.H.Deps)
+
+	in := gtime.Date(2025, gtime.March, 31, 15, 0, 0, 0, gtime.UTC)
+
+	tests := []struct {
+		name    string
+		tzn     string // time zone name
+		want    string
+		wantErr bool
+	}{
+		{name: "A", tzn: "America/Denver", want: "2025-03-31T09:00:00-06:00", wantErr: false},
+		{name: "B", tzn: "Australia/Adelaide", want: "2025-04-01T01:30:00+10:30", wantErr: false},
+		{name: "C", tzn: "Europe/Oslo", want: "2025-03-31T17:00:00+02:00", wantErr: false},
+		{name: "D", tzn: "UTC", want: "2025-03-31T15:00:00+00:00", wantErr: false},
+		{name: "E", tzn: "", want: "2025-03-31T15:00:00+00:00", wantErr: false},
+		{name: "F", tzn: "InvalidTimeZoneName", want: "0001-01-01T00:00:00+00:00", wantErr: true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := ns.In(tt.tzn, in)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("time.In() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			got := result.Format("2006-01-02T15:04:05-07:00")
+			if got != tt.want {
+				t.Errorf("time.In() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+// For benchmark tests below.
+var timeZoneNames []string = []string{"America/New_York", "Europe/Oslo", "Australia/Sydney", "UTC", "Local"}
+
+func BenchmarkInWithCaching(b *testing.B) {
+	bb := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{T: b},
+	).Build()
+
+	ns := time.New(htime.NewTimeFormatter(translators.GetTranslator("en")), gtime.UTC, bb.H.Deps)
+
+	for i := 0; i < b.N; i++ {
+		timeZoneName := timeZoneNames[i%len(timeZoneNames)]
+		_, err := ns.In(timeZoneName, gtime.Now())
+		if err != nil {
+			b.Fatalf("Error during benchmark: %v", err)
+		}
+	}
+}
+
+func BenchmarkInWithoutCaching(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		timeZoneName := timeZoneNames[i%len(timeZoneNames)]
+		location, err := gtime.LoadLocation(timeZoneName)
+		if err != nil {
+			b.Fatalf("Error during benchmark: %v", err)
+		}
+
+		_ = gtime.Now().In(location)
+	}
+}