Add render template hooks for headings

This commit also

* Renames previous types to be non-specific. (e.g. hookedRenderer rather
  than linkRenderer)

Resolves #6713

hugolib/page.go

@@ -375,48 +375,54 @@ func (ps *pageState) initCommonProviders(pp pagePaths) error {
 	return nil
 }
 
-func (p *pageState) createRenderHooks(f output.Format) (*hooks.Render, error) {
-
+func (p *pageState) createRenderHooks(f output.Format) (*hooks.Renderers, error) {
 	layoutDescriptor := p.getLayoutDescriptor()
 	layoutDescriptor.RenderingHook = true
 	layoutDescriptor.LayoutOverride = false
 	layoutDescriptor.Layout = ""
 
+	var renderers hooks.Renderers
+
 	layoutDescriptor.Kind = "render-link"
-	linkTempl, linkTemplFound, err := p.s.Tmpl().LookupLayout(layoutDescriptor, f)
+	templ, templFound, err := p.s.Tmpl().LookupLayout(layoutDescriptor, f)
 	if err != nil {
 		return nil, err
 	}
+	if templFound {
+		renderers.LinkRenderer = hookRenderer{
+			templateHandler: p.s.Tmpl(),
+			Provider:        templ.(tpl.Info),
+			templ:           templ,
+		}
+	}
 
 	layoutDescriptor.Kind = "render-image"
-	imgTempl, imgTemplFound, err := p.s.Tmpl().LookupLayout(layoutDescriptor, f)
+	templ, templFound, err = p.s.Tmpl().LookupLayout(layoutDescriptor, f)
 	if err != nil {
 		return nil, err
 	}
-
-	var linkRenderer hooks.LinkRenderer
-	var imageRenderer hooks.LinkRenderer
-
-	if linkTemplFound {
-		linkRenderer = contentLinkRenderer{
+	if templFound {
+		renderers.ImageRenderer = hookRenderer{
 			templateHandler: p.s.Tmpl(),
-			Provider:        linkTempl.(tpl.Info),
-			templ:           linkTempl,
+			Provider:        templ.(tpl.Info),
+			templ:           templ,
 		}
 	}
 
-	if imgTemplFound {
-		imageRenderer = contentLinkRenderer{
+	layoutDescriptor.Kind = "render-heading"
+	templ, templFound, err = p.s.Tmpl().LookupLayout(layoutDescriptor, f)
+	if err != nil {
+		return nil, err
+	}
+	if templFound {
+		renderers.HeadingRenderer = hookRenderer{
 			templateHandler: p.s.Tmpl(),
-			Provider:        imgTempl.(tpl.Info),
-			templ:           imgTempl,
+			Provider:        templ.(tpl.Info),
+			templ:           templ,
 		}
 	}
 
-	return &hooks.Render{
-		LinkRenderer:  linkRenderer,
-		ImageRenderer: imageRenderer,
-	}, nil
+	return &renderers, nil
 }
 
 func (p *pageState) getLayoutDescriptor() output.LayoutDescriptor {

hugolib/page__per_output.go

@@ -245,7 +245,7 @@ type pageContentOutput struct {
 	placeholdersEnabledInit sync.Once
 
 	// May be nil.
-	renderHooks *hooks.Render
+	renderHooks *hooks.Renderers
 	// Set if there are more than one output format variant
 	renderHooksHaveVariants bool // TODO(bep) reimplement this in another way, consolidate with shortcodes
 

hugolib/site.go

@@ -1650,14 +1650,20 @@ var infoOnMissingLayout = map[string]bool{
 	"404": true,
 }
 
-type contentLinkRenderer struct {
+// hookRenderer is the canonical implementation of all hooks.ITEMRenderer,
+// where ITEM is the thing being hooked.
+type hookRenderer struct {
 	templateHandler tpl.TemplateHandler
 	identity.Provider
 	templ tpl.Template
 }
 
-func (r contentLinkRenderer) Render(w io.Writer, ctx hooks.LinkContext) error {
-	return r.templateHandler.Execute(r.templ, w, ctx)
+func (hr hookRenderer) RenderLink(w io.Writer, ctx hooks.LinkContext) error {
+	return hr.templateHandler.Execute(hr.templ, w, ctx)
+}
+
+func (hr hookRenderer) RenderHeading(w io.Writer, ctx hooks.HeadingContext) error {
+	return hr.templateHandler.Execute(hr.templ, w, ctx)
 }
 
 func (s *Site) renderForTemplate(name, outputFormat string, d interface{}, w io.Writer, templ tpl.Template) (err error) {

markup/converter/converter.go

@@ -126,7 +126,7 @@ type DocumentContext struct {
 type RenderContext struct {
 	Src         []byte
 	RenderTOC   bool
-	RenderHooks *hooks.Render
+	RenderHooks *hooks.Renderers
 }
 
 var (

markup/converter/hooks/hooks.go

@@ -27,13 +27,41 @@ type LinkContext interface {
 	PlainText() string
 }
 
-type Render struct {
-	LinkRenderer  LinkRenderer
-	ImageRenderer LinkRenderer
+type LinkRenderer interface {
+	RenderLink(w io.Writer, ctx LinkContext) error
+	identity.Provider
+}
+
+// HeadingContext contains accessors to all attributes that a HeadingRenderer
+// can use to render a heading.
+type HeadingContext interface {
+	// Page is the page containing the heading.
+	Page() interface{}
+	// Level is the level of the header (i.e. 1 for top-level, 2 for sub-level, etc.).
+	Level() int
+	// Anchor is the HTML id assigned to the heading.
+	Anchor() string
+	// Text is the rendered (HTML) heading text, excluding the heading marker.
+	Text() string
+	// PlainText is the unrendered version of Text.
+	PlainText() string
+}
+
+// HeadingRenderer describes a uniquely identifiable rendering hook.
+type HeadingRenderer interface {
+	// Render writes the renderered content to w using the data in w.
+	RenderHeading(w io.Writer, ctx HeadingContext) error
+	identity.Provider
 }
 
-func (r *Render) Eq(other interface{}) bool {
-	ro, ok := other.(*Render)
+type Renderers struct {
+	LinkRenderer    LinkRenderer
+	ImageRenderer   LinkRenderer
+	HeadingRenderer HeadingRenderer
+}
+
+func (r *Renderers) Eq(other interface{}) bool {
+	ro, ok := other.(*Renderers)
 	if !ok {
 		return false
 	}
@@ -49,10 +77,9 @@ func (r *Render) Eq(other interface{}) bool {
 		return false
 	}
 
-	return true
-}
+	if r.HeadingRenderer.GetIdentity() != ro.HeadingRenderer.GetIdentity() {
+		return false
+	}
 
-type LinkRenderer interface {
-	Render(w io.Writer, ctx LinkContext) error
-	identity.Provider
+	return true
 }