Add a page template func

Fixes #9339

resources/errorResource.go

@@ -135,3 +135,7 @@ func (e *errorResource) DecodeImage() (image.Image, error) {
 func (e *errorResource) Transform(...ResourceTransformation) (ResourceTransformer, error) {
 	panic(e.ResourceError)
 }
+
+func (e *errorResource) TransformWithContext(context.Context, ...ResourceTransformation) (ResourceTransformer, error) {
+	panic(e.ResourceError)
+}

resources/page/pagegroup.go

@@ -159,12 +159,7 @@ func (p Pages) GroupBy(ctx context.Context, key string, order ...string) (PagesG
 		case reflect.StructField:
 			fv = ppv.Elem().FieldByName(key)
 		case reflect.Method:
-			var args []reflect.Value
-			fn := hreflect.GetMethodByName(ppv, key)
-			if fn.Type().NumIn() > 0 && fn.Type().In(0).Implements(hreflect.ContextInterface) {
-				args = []reflect.Value{reflect.ValueOf(ctx)}
-			}
-			fv = fn.Call(args)[0]
+			fv = hreflect.CallMethodByName(ctx, key, ppv)[0]
 		}
 		if !fv.IsValid() {
 			continue

resources/resource.go

@@ -104,6 +104,7 @@ type ResourceTransformer interface {
 
 type Transformer interface {
 	Transform(...ResourceTransformation) (ResourceTransformer, error)
+	TransformWithContext(context.Context, ...ResourceTransformation) (ResourceTransformer, error)
 }
 
 func NewFeatureNotAvailableTransformer(key string, elements ...any) ResourceTransformation {

resources/resource_transformers/templates/execute_as_template.go

@@ -15,6 +15,7 @@
 package templates
 
 import (
+	"context"
 	"fmt"
 
 	"github.com/gohugoio/hugo/helpers"
@@ -61,11 +62,11 @@ func (t *executeAsTemplateTransform) Transform(ctx *resources.ResourceTransforma
 
 	ctx.OutPath = t.targetPath
 
-	return t.t.Tmpl().Execute(templ, ctx.To, t.data)
+	return t.t.Tmpl().ExecuteWithContext(ctx.Ctx, templ, ctx.To, t.data)
 }
 
-func (c *Client) ExecuteAsTemplate(res resources.ResourceTransformer, targetPath string, data any) (resource.Resource, error) {
-	return res.Transform(&executeAsTemplateTransform{
+func (c *Client) ExecuteAsTemplate(ctx context.Context, res resources.ResourceTransformer, targetPath string, data any) (resource.Resource, error) {
+	return res.TransformWithContext(ctx, &executeAsTemplateTransform{
 		rs:         c.rs,
 		targetPath: helpers.ToSlashTrimLeading(targetPath),
 		t:          c.t,

resources/transform.go

@@ -69,6 +69,7 @@ func newResourceAdapter(spec *Spec, lazyPublish bool, target transformableResour
 	return &resourceAdapter{
 		resourceTransformations: &resourceTransformations{},
 		resourceAdapterInner: &resourceAdapterInner{
+			ctx:         context.TODO(),
 			spec:        spec,
 			publishOnce: po,
 			target:      target,
@@ -84,6 +85,9 @@ type ResourceTransformation interface {
 }
 
 type ResourceTransformationCtx struct {
+	// The context that started the transformation.
+	Ctx context.Context
+
 	// The content to transform.
 	From io.Reader
 
@@ -180,6 +184,7 @@ func (r *resourceAdapter) Data() any {
 func (r resourceAdapter) cloneTo(targetPath string) resource.Resource {
 	newtTarget := r.target.cloneTo(targetPath)
 	newInner := &resourceAdapterInner{
+		ctx:    r.ctx,
 		spec:   r.spec,
 		target: newtTarget.(transformableResource),
 	}
@@ -278,11 +283,17 @@ func (r *resourceAdapter) Title() string {
 }
 
 func (r resourceAdapter) Transform(t ...ResourceTransformation) (ResourceTransformer, error) {
+	return r.TransformWithContext(context.Background(), t...)
+}
+
+func (r resourceAdapter) TransformWithContext(ctx context.Context, t ...ResourceTransformation) (ResourceTransformer, error) {
+
 	r.resourceTransformations = &resourceTransformations{
 		transformations: append(r.transformations, t...),
 	}
 
 	r.resourceAdapterInner = &resourceAdapterInner{
+		ctx:         ctx,
 		spec:        r.spec,
 		publishOnce: &publishOnce{},
 		target:      r.target,
@@ -377,6 +388,7 @@ func (r *resourceAdapter) transform(publish, setContent bool) error {
 	defer bp.PutBuffer(b2)
 
 	tctx := &ResourceTransformationCtx{
+		Ctx:                   r.ctx,
 		Data:                  make(map[string]any),
 		OpenResourcePublisher: r.target.openPublishFileForWriting,
 	}
@@ -599,6 +611,9 @@ func (r *resourceAdapter) initTransform(publish, setContent bool) {
 }
 
 type resourceAdapterInner struct {
+	// The context that started this transformation.
+	ctx context.Context
+
 	target transformableResource
 
 	spec *Spec