tpl/collections: Fix apply when function have Context as first arg

As introduced in `partial` and `partialCached` in Hugo 0.93.0.

Fixes #9585

tpl/collections/apply.go

@@ -14,16 +14,18 @@
 package collections
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"reflect"
 	"strings"
 
+	"github.com/gohugoio/hugo/common/hreflect"
 	"github.com/gohugoio/hugo/tpl"
 )
 
 // Apply takes a map, array, or slice and returns a new slice with the function fname applied over it.
-func (ns *Namespace) Apply(seq interface{}, fname string, args ...interface{}) (interface{}, error) {
+func (ns *Namespace) Apply(ctx context.Context, seq interface{}, fname string, args ...interface{}) (interface{}, error) {
 	if seq == nil {
 		return make([]interface{}, 0), nil
 	}
@@ -43,15 +45,13 @@ func (ns *Namespace) Apply(seq interface{}, fname string, args ...interface{}) (
 		return nil, errors.New("can't find function " + fname)
 	}
 
-	// fnv := reflect.ValueOf(fn)
-
 	switch seqv.Kind() {
 	case reflect.Array, reflect.Slice:
 		r := make([]interface{}, seqv.Len())
 		for i := 0; i < seqv.Len(); i++ {
 			vv := seqv.Index(i)
 
-			vvv, err := applyFnToThis(fnv, vv, args...)
+			vvv, err := applyFnToThis(ctx, fnv, vv, args...)
 			if err != nil {
 				return nil, err
 			}
@@ -65,7 +65,12 @@ func (ns *Namespace) Apply(seq interface{}, fname string, args ...interface{}) (
 	}
 }
 
-func applyFnToThis(fn, this reflect.Value, args ...interface{}) (reflect.Value, error) {
+func applyFnToThis(ctx context.Context, fn, this reflect.Value, args ...interface{}) (reflect.Value, error) {
+	num := fn.Type().NumIn()
+	if num > 0 && fn.Type().In(0).Implements(hreflect.ContextInterface) {
+		args = append([]interface{}{ctx}, args...)
+	}
+
 	n := make([]reflect.Value, len(args))
 	for i, arg := range args {
 		if arg == "." {
@@ -75,8 +80,6 @@ func applyFnToThis(fn, this reflect.Value, args ...interface{}) (reflect.Value,
 		}
 	}
 
-	num := fn.Type().NumIn()
-
 	if fn.Type().IsVariadic() {
 		num--
 	}