tpl: Refactor time.AsTime location implementation

docs/content/en/functions/time.md

@@ -13,13 +13,13 @@ menu:
 keywords: [dates,time,location]
 signature: ["time INPUT [LOCATION]"]
 workson: []
-hugoversion:
+hugoversion: "v0.77.0"
 relatedfuncs: []
 deprecated: false
 aliases: []
 ---
 
-`time` converts a timestamp string with an optional timezone into a [`time.Time`](https://godoc.org/time#Time) structure so you can access its fields:
+`time` converts a timestamp string with an optional default location into a [`time.Time`](https://godoc.org/time#Time) structure so you can access its fields:
 
 ```
 {{ time "2016-05-28" }} → "2016-05-28T00:00:00Z"
@@ -27,9 +27,11 @@ aliases: []
 {{ mul 1000 (time "2016-05-28T10:30:00.00+10:00").Unix }} → 1464395400000, or Unix time in milliseconds
 ```
 
-## Using Timezone
+## Using Locations
 
-The optional 2nd parameter [LOCATION] argument is a string that references a timezone that is associated with the specified time value. If the time value has an explicit timezone or offset specified, it will take precedence over an explicit [LOCATION].
+The optional `LOCATION` parameter is a string that sets a default location that is associated with the specified time value. If the time value has an explicit timezone or offset specified, it will take precedence over the `LOCATION` parameter.
+
+The list of valid locations may be system dependent, but should include `UTC`, `Local`, or any location in the [IANA Time Zone database](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones).
 
 ```
 {{ time "2020-10-20" }} → 2020-10-20 00:00:00 +0000 UTC
@@ -37,8 +39,6 @@ The optional 2nd parameter [LOCATION] argument is a string that references a tim
 {{ time "2020-01-20" "America/Los_Angeles" }} → 2020-01-20 00:00:00 -0800 PST
 ```
 
-> **Note**: Timezone support via the [LOCATION] parameter is included with Hugo `0.77`.
-
 ## Example: Using `time` to get Month Index
 
 The following example takes a UNIX timestamp---set as `utimestamp: "1489276800"` in a content's front matter---converts the timestamp (string) to an integer using the [`int` function][int], and then uses [`printf`][] to convert the `Month` property of `time` into an index.

tpl/time/time.go

@@ -21,49 +21,7 @@ import (
 	"github.com/spf13/cast"
 )
 
-// New returns a new instance of the time-namespaced template functions.
-func New() *Namespace {
-	return &Namespace{}
-}
-
-// Namespace provides template functions for the "time" namespace.
-type Namespace struct{}
-
-// AsTime converts the textual representation of the datetime string into
-// a time.Time interface.
-func (ns *Namespace) AsTime(v interface{}, args ...interface{}) (interface{}, error) {
-	t, err := cast.ToTimeE(v)
-	if err != nil {
-		return nil, err
-	}
-
-	if len(args) == 0 {
-		return t, nil
-	}
-
-	// Otherwise, if a location is specified, attempt to parse the time using the location specified.
-	// Note: In this case, we require the input variable to be a string for proper parsing.
-	// Note: We can't convert an existing parsed time by using the `Time.In()` as this CONVERTS/MODIFIES
-	//       the resulting time.
-
-	switch givenType := v.(type) {
-	case string:
-		// Good, we only support strings
-		break
-
-	default:
-		return nil, fmt.Errorf("Creating a time instance with location requires a value of type String. Given type: %s", givenType)
-	}
-
-	location, err := _time.LoadLocation(args[0].(string))
-	if err != nil {
-		return nil, err
-	}
-
-	// Note: Cast currently doesn't support time with non-default locations. For now, just inlining this.
-	// Reference: https://github.com/spf13/cast/pull/80
-
-	fmts := []string{
+var timeFormats = []string{
 	_time.RFC3339,
 	"2006-01-02T15:04:05", // iso8601 without timezone
 	_time.RFC1123Z,
@@ -90,14 +48,52 @@ func (ns *Namespace) AsTime(v interface{}, args ...interface{}) (interface{}, er
 	_time.StampNano,
 }
 
-	for _, dateType := range fmts {
-		t, err := _time.ParseInLocation(dateType, v.(string), location)
-		if err == nil {
+// New returns a new instance of the time-namespaced template functions.
+func New() *Namespace {
+	return &Namespace{}
+}
+
+// Namespace provides template functions for the "time" namespace.
+type Namespace struct{}
+
+// AsTime converts the textual representation of the datetime string into
+// a time.Time interface.
+func (ns *Namespace) AsTime(v interface{}, args ...interface{}) (interface{}, error) {
+	if len(args) == 0 {
+		t, err := cast.ToTimeE(v)
+		if err != nil {
+			return nil, err
+		}
+
+		return t, nil
+	}
+
+	timeStr, err := cast.ToStringE(v)
+	if err != nil {
+		return nil, err
+	}
+
+	locStr, err := cast.ToStringE(args[0])
+	if err != nil {
+		return nil, err
+	}
+
+	loc, err := _time.LoadLocation(locStr)
+	if err != nil {
+		return nil, err
+	}
+
+	// Note: Cast currently doesn't support time with non-default locations. For now, just inlining this.
+	// Reference: https://github.com/spf13/cast/pull/80
+
+	for _, dateType := range timeFormats {
+		t, err2 := _time.ParseInLocation(dateType, timeStr, loc)
+		if err2 == nil {
 			return t, nil
 		}
 	}
 
-	return nil, fmt.Errorf("Unable to ParseInLocation using date \"%s\" with timezone \"%s\"", v, location)
+	return nil, fmt.Errorf("Unable to ParseInLocation using date %q with timezone %q", v, loc)
 }
 
 // Format converts the textual representation of the datetime string into