tpl: updates cast.ToTruth to conform to hreflect.IsTruthful

Concession from review, where cast.ToTruth should behave exactly like hreflect.IsTruthful.
Additionally, cast.ToBool always returns a bool with nil error.

docs/content/en/functions/truth.md

@@ -20,23 +20,21 @@ aliases: []
 
 Useful for turning different types into booleans based on their [truthy-ness](https://developer.mozilla.org/en-US/docs/Glossary/Truthy).
 
-It follows the same rules as [`bool`](/functions/bool), but with increased flexibility.
-
 ```
 {{ truth "true" }} → true
-{{ truth "false" }} → false
+{{ truth "false" }} → true
 
 {{ truth "TRUE" }} → true
-{{ truth "FALSE" }} → false
+{{ truth "FALSE" }} → true
 
 {{ truth "t" }} → true
-{{ truth "f" }} → false
+{{ truth "f" }} → true
 
 {{ truth "T" }} → true
-{{ truth "F" }} → false
+{{ truth "F" }} → true
 
 {{ truth "1" }} → true
-{{ truth "0" }} → false
+{{ truth "0" }} → true
 
 {{ truth 1 }} → true
 {{ truth 0 }} → false

tpl/cast/cast.go

@@ -17,6 +17,7 @@ package cast
 import (
 	"html/template"
 
+	"github.com/gohugoio/hugo/common/hreflect"
 	_cast "github.com/spf13/cast"
 )
 
@@ -49,23 +50,18 @@ func (ns *Namespace) ToFloat(v any) (float64, error) {
 // ToBool converts v to a boolean.
 func (ns *Namespace) ToBool(v any) (bool, error) {
 	v = convertTemplateToString(v)
-	return _cast.ToBoolE(v)
+	result, err := _cast.ToBoolE(v)
+	if err != nil {
+		return false, nil
+	}
+	return result, nil
 }
 
 // ToTruth yields the same behavior as ToBool when possible.
 // If the cast is unsuccessful, ToTruth converts v to a boolean using the JavaScript [definition of truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy).
 // Accordingly, it never yields an error, but maintains the signature of other cast methods for consistency.
 func (ns *Namespace) ToTruth(v any) (bool, error) {
-	result, err := ns.ToBool(v)
-	if err != nil {
-		switch v {
-		case "", "nil", "null", "undefined", "NaN":
-			return false, nil
-		default:
-			return true, nil
-		}
-	}
-	return result, nil
+	return hreflect.IsTruthful(v), nil
 }
 
 func convertTemplateToString(v any) any {

tpl/cast/cast_test.go

@@ -144,10 +144,8 @@ func TestToBool(t *testing.T) {
 		{false, false, nil},
 		{nil, false, nil},
 
-		// error cases
-		{"cheese", nil, false},
-		{"", nil, false},
-		{1.67, nil, false},
+		{"cheese", false, nil},
+		{"", false, nil},
 	} {
 		errMsg := qt.Commentf("[%d] %v", i, test.v)
 
@@ -173,15 +171,15 @@ func TestToTruth(t *testing.T) {
 		expect any
 	}{
 		{"true", true},
-		{"false", false},
+		{"false", true},
 		{"TRUE", true},
-		{"FALSE", false},
+		{"FALSE", true},
 		{"t", true},
-		{"f", false},
+		{"f", true},
 		{"T", true},
-		{"F", false},
+		{"F", true},
 		{"1", true},
-		{"0", false},
+		{"0", true},
 		{1, true},
 		{0, false},
 		{"cheese", true},
@@ -194,9 +192,9 @@ func TestToTruth(t *testing.T) {
 		{template.JSStr("6"), true},
 		{t, true},
 		{nil, false},
-		{"null", false},
-		{"undefined", false},
-		{"NaN", false},
+		{"null", true},
+		{"undefined", true},
+		{"NaN", true},
 	} {
 		errMsg := qt.Commentf("[%d] %v", i, test.v)