Implement defer

Closes #8086
Closes #12589

7 files changed, 452 insertions, 23 deletions

diff --git a/tpl/template.go b/tpl/template.go
index 0ab1abf2f..cb8d2b321 100644
--- a/tpl/template.go
+++ b/tpl/template.go
@@ -20,11 +20,13 @@ import (
 	"reflect"
 	"regexp"
 	"strings"
+	"sync"
 	"unicode"
 
 	bp "github.com/gohugoio/hugo/bufferpool"
 	"github.com/gohugoio/hugo/common/hcontext"
 	"github.com/gohugoio/hugo/identity"
+	"github.com/gohugoio/hugo/langs"
 	"github.com/gohugoio/hugo/output/layouts"
 
 	"github.com/gohugoio/hugo/output"
@@ -160,6 +162,11 @@ type TemplateFuncGetter interface {
 	GetFunc(name string) (reflect.Value, bool)
 }
 
+type RenderingContext struct {
+	Site       site
+	SiteOutIdx int
+}
+
 type contextKey string
 
 // Context manages values passed in the context to templates.
@@ -191,6 +198,15 @@ type page interface {
 	IsNode() bool
 }
 
+type site interface {
+	Language() *langs.Language
+}
+
+const (
+	HugoDeferredTemplatePrefix = "__hdeferred/"
+	HugoDeferredTemplateSuffix = "__d="
+)
+
 const hugoNewLinePlaceholder = "___hugonl_"
 
 var stripHTMLReplacerPre = strings.NewReplacer("\n", " ", "</p>", hugoNewLinePlaceholder, "<br>", hugoNewLinePlaceholder, "<br />", hugoNewLinePlaceholder)
@@ -228,3 +244,13 @@ func StripHTML(s string) string {
 
 	return s
 }
+
+type DeferredExecution struct {
+	Mu           sync.Mutex
+	Ctx          context.Context
+	TemplateName string
+	Data         any
+
+	Executed bool
+	Result   string
+}
diff --git a/tpl/templates/defer_integration_test.go b/tpl/templates/defer_integration_test.go
new file mode 100644
index 000000000..2c2bf0d80
--- /dev/null
+++ b/tpl/templates/defer_integration_test.go
@@ -0,0 +1,202 @@
+// Copyright 2024 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package templates_test
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	qt "github.com/frankban/quicktest"
+
+	"github.com/gohugoio/hugo/hugolib"
+)
+
+const deferFilesCommon = `
+-- hugo.toml --
+disableLiveReload = true
+disableKinds = ["taxonomy", "term", "rss", "sitemap", "robotsTXT", "404", "section"]
+[languages]
+[languages.en]
+weight = 1
+[languages.nn]
+weight = 2
+-- i18n/en.toml --
+[hello]
+other = "Hello"
+-- i18n/nn.toml --
+[hello]
+other = "Hei"
+-- content/_index.en.md --
+---
+title: "Home"
+outputs: ["html", "amp"]
+---
+-- content/_index.nn.md --
+---
+title: "Heim"
+outputs: ["html", "amp"]
+---
+-- assets/mytext.txt --
+Hello.
+-- layouts/baseof.html --
+HTML|{{ block "main" . }}{{ end }}$
+-- layouts/index.html --
+{{ define "main" }}
+EDIT_COUNTER_OUTSIDE_0
+{{ .Store.Set "hello" "Hello" }}
+{{ $data := dict "page" . }}
+{{ with (templates.Defer (dict "data" $data) ) }}
+{{ $mytext := resources.Get "mytext.txt" }}
+REPLACE_ME|Title: {{ .page.Title }}|{{ .page.RelPermalink }}|Hello: {{ T "hello" }}|Hello Store: {{ .page.Store.Get "hello" }}|Mytext: {{ $mytext.Content }}|
+EDIT_COUNTER_DEFER_0
+{{ end }}$
+{{ end }}
+-- layouts/index.amp.html --
+AMP.
+{{ $data := dict "page" . }}
+{{ with (templates.Defer (dict "data" $data) ) }}Title AMP: {{ .page.Title }}|{{ .page.RelPermalink }}|Hello: {{ T "hello" }}{{ end }}$
+
+`
+
+func TestDeferBasic(t *testing.T) {
+	t.Parallel()
+
+	b := hugolib.Test(t, deferFilesCommon)
+
+	b.AssertFileContent("public/index.html", "Title: Home|/|Hello: Hello|Hello Store: Hello|Mytext: Hello.|")
+	b.AssertFileContent("public/amp/index.html", "Title AMP: Home|/amp/|Hello: Hello")
+	b.AssertFileContent("public/nn/index.html", "Title: Heim|/nn/|Hello: Hei")
+	b.AssertFileContent("public/nn/amp/index.html", "Title AMP: Heim|/nn/amp/|Hello: Hei")
+}
+
+func TestDeferRepeatedBuildsEditOutside(t *testing.T) {
+	t.Parallel()
+
+	b := hugolib.TestRunning(t, deferFilesCommon)
+
+	for i := 0; i < 5; i++ {
+		old := fmt.Sprintf("EDIT_COUNTER_OUTSIDE_%d", i)
+		new := fmt.Sprintf("EDIT_COUNTER_OUTSIDE_%d", i+1)
+		b.EditFileReplaceAll("layouts/index.html", old, new).Build()
+		b.AssertFileContent("public/index.html", new)
+	}
+}
+
+func TestDeferRepeatedBuildsEditDefer(t *testing.T) {
+	t.Parallel()
+
+	b := hugolib.TestRunning(t, deferFilesCommon)
+
+	for i := 0; i < 8; i++ {
+		old := fmt.Sprintf("EDIT_COUNTER_DEFER_%d", i)
+		new := fmt.Sprintf("EDIT_COUNTER_DEFER_%d", i+1)
+		b.EditFileReplaceAll("layouts/index.html", old, new).Build()
+		b.AssertFileContent("public/index.html", new)
+	}
+}
+
+func TestDeferErrorParse(t *testing.T) {
+	t.Parallel()
+
+	b, err := hugolib.TestE(t, strings.ReplaceAll(deferFilesCommon, "Title AMP: {{ .page.Title }}", "{{ .page.Title }"))
+
+	b.Assert(err, qt.Not(qt.IsNil))
+	b.Assert(err.Error(), qt.Contains, `index.amp.html:3: unexpected "}" in operand`)
+}
+
+func TestDeferErrorRuntime(t *testing.T) {
+	t.Parallel()
+
+	b, err := hugolib.TestE(t, strings.ReplaceAll(deferFilesCommon, "Title AMP: {{ .page.Title }}", "{{ .page.Titles }}"))
+
+	b.Assert(err, qt.Not(qt.IsNil))
+	b.Assert(err.Error(), qt.Contains, filepath.FromSlash(`/layouts/index.amp.html:3:57`))
+	b.Assert(err.Error(), qt.Contains, `execute of template failed: template: index.amp.html:3:57: executing at <.page.Titles>: can't evaluate field Titles`)
+}
+
+func TestDeferEditDeferBlock(t *testing.T) {
+	t.Parallel()
+
+	b := hugolib.TestRunning(t, deferFilesCommon)
+	b.AssertRenderCountPage(4)
+	b.EditFileReplaceAll("layouts/index.html", "REPLACE_ME", "Edited.").Build()
+	b.AssertFileContent("public/index.html", "Edited.")
+	b.AssertRenderCountPage(2)
+}
+
+//
+
+func TestDeferEditResourceUsedInDeferBlock(t *testing.T) {
+	t.Parallel()
+
+	b := hugolib.TestRunning(t, deferFilesCommon)
+	b.AssertRenderCountPage(4)
+	b.EditFiles("assets/mytext.txt", "Mytext Hello Edited.").Build()
+	b.AssertFileContent("public/index.html", "Mytext Hello Edited.")
+	b.AssertRenderCountPage(2)
+}
+
+func TestDeferMountPublic(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+[module]
+[[module.mounts]]
+source = "content"
+target = "content"
+[[module.mounts]]
+source = "layouts"
+target = "layouts"
+[[module.mounts]]
+source = 'public'
+target = 'assets/public'
+disableWatch = true
+-- layouts/index.html --
+Home.
+{{ $mydata := dict "v1" "v1value" }}
+{{ $json := resources.FromString "mydata/data.json" ($mydata | jsonify ) }}
+{{ $nop := $json.RelPermalink }}
+{{ with (templates.Defer (dict "key" "foo")) }}
+	  {{ $jsonFilePublic := resources.Get "public/mydata/data.json" }}
+	  {{ with  $jsonFilePublic }}
+      {{ $m := $jsonFilePublic | transform.Unmarshal }}
+	  v1: {{ $m.v1 }}
+	  {{ end }}
+{{ end }}
+`
+
+	b := hugolib.Test(t, files)
+
+	b.AssertFileContent("public/index.html", "v1: v1value")
+}
+
+func TestDeferFromContentAdapterShouldFail(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+-- content/_content.gotmpl --
+{{ with (templates.Defer (dict "key" "foo")) }}
+ Foo.
+{{ end }}
+`
+
+	b, err := hugolib.TestE(t, files)
+
+	b.Assert(err, qt.Not(qt.IsNil))
+	b.Assert(err.Error(), qt.Contains, "error calling Defer: this method cannot be called before the site is fully initialized")
+}
diff --git a/tpl/templates/init.go b/tpl/templates/init.go
index ff6acdabd..7bd1f50c5 100644
--- a/tpl/templates/init.go
+++ b/tpl/templates/init.go
@@ -39,6 +39,16 @@ func init() {
 			},
 		)
 
+		ns.AddMethodMapping(ctx.Defer,
+			nil, // No aliases to keep the AST parsing simple.
+			[][2]string{},
+		)
+
+		ns.AddMethodMapping(ctx.DoDefer,
+			[]string{"doDefer"},
+			[][2]string{},
+		)
+
 		return ns
 	}
 
diff --git a/tpl/templates/templates.go b/tpl/templates/templates.go
index 8e40f3443..91e96ed8e 100644
--- a/tpl/templates/templates.go
+++ b/tpl/templates/templates.go
@@ -15,14 +15,24 @@
 package templates
 
 import (
+	"context"
+	"fmt"
+	"strconv"
+	"sync/atomic"
+
 	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/tpl"
+	"github.com/mitchellh/mapstructure"
 )
 
 // New returns a new instance of the templates-namespaced template functions.
 func New(deps *deps.Deps) *Namespace {
-	return &Namespace{
+	ns := &Namespace{
 		deps: deps,
 	}
+
+	return ns
 }
 
 // Namespace provides template functions for the "templates" namespace.
@@ -36,3 +46,59 @@ type Namespace struct {
 func (ns *Namespace) Exists(name string) bool {
 	return ns.deps.Tmpl().HasTemplate(name)
 }
+
+// Defer defers the execution of a template block.
+func (ns *Namespace) Defer(args ...any) (bool, error) {
+	// Prevent defer from being used in content adapters,
+	// that just doesn't work.
+	ns.deps.Site.CheckReady()
+
+	if len(args) != 0 {
+		return false, fmt.Errorf("Defer does not take any arguments")
+	}
+	return true, nil
+}
+
+var defferedIDCounter atomic.Uint64
+
+type DeferOpts struct {
+	// Optional cache key. If set, the deferred block will be executed
+	// once per unique key.
+	Key string
+
+	// Optional data context to use when executing the deferred block.
+	Data any
+}
+
+// DoDefer defers the execution of a template block.
+// For internal use only.
+func (ns *Namespace) DoDefer(ctx context.Context, id string, optsv any) string {
+	var opts DeferOpts
+	if optsv != nil {
+		if err := mapstructure.WeakDecode(optsv, &opts); err != nil {
+			panic(err)
+		}
+	}
+
+	templateName := id
+	var key string
+	if opts.Key != "" {
+		key = helpers.MD5String(opts.Key)
+	} else {
+		key = strconv.FormatUint(defferedIDCounter.Add(1), 10)
+	}
+
+	id = fmt.Sprintf("%s_%s%s", id, key, tpl.HugoDeferredTemplateSuffix)
+
+	_ = ns.deps.BuildState.DeferredExecutions.Executions.GetOrCreate(id,
+		func() *tpl.DeferredExecution {
+			return &tpl.DeferredExecution{
+				TemplateName: templateName,
+				Ctx:          ctx,
+				Data:         opts.Data,
+				Executed:     false,
+			}
+		})
+
+	return id
+}
diff --git a/tpl/tplimpl/template.go b/tpl/tplimpl/template.go
index 63dc29662..04ccdaad2 100644
--- a/tpl/tplimpl/template.go
+++ b/tpl/tplimpl/template.go
@@ -42,6 +42,7 @@ import (
 
 	"github.com/gohugoio/hugo/common/herrors"
 	"github.com/gohugoio/hugo/hugofs"
+	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
 
 	htmltemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
 	texttemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"
@@ -194,11 +195,12 @@ func newTemplateNamespace(funcs map[string]any) *templateNamespace {
 	}
 }
 
-func newTemplateState(templ tpl.Template, info templateInfo, id identity.Identity) *templateState {
+func newTemplateState(owner *templateState, templ tpl.Template, info templateInfo, id identity.Identity) *templateState {
 	if id == nil {
 		id = info
 	}
 	return &templateState{
+		owner:     owner,
 		info:      info,
 		typ:       info.resolveType(),
 		Template:  templ,
@@ -260,7 +262,11 @@ func (t *templateExec) ExecuteWithContext(ctx context.Context, templ tpl.Templat
 
 	execErr := t.executor.ExecuteWithContext(ctx, templ, wr, data)
 	if execErr != nil {
-		execErr = t.addFileContext(templ, execErr)
+		owner := templ
+		if ts, ok := templ.(*templateState); ok && ts.owner != nil {
+			owner = ts.owner
+		}
+		execErr = t.addFileContext(owner, execErr)
 	}
 	return execErr
 }
@@ -312,6 +318,9 @@ func (t *templateExec) MarkReady() error {
 		// We only need the clones if base templates are in use.
 		if len(t.needsBaseof) > 0 {
 			err = t.main.createPrototypes()
+			if err != nil {
+				return
+			}
 		}
 	})
 
@@ -369,7 +378,7 @@ type layoutCacheEntry struct {
 func (t *templateHandler) AddTemplate(name, tpl string) error {
 	templ, err := t.addTemplateTo(t.newTemplateInfo(name, tpl), t.main)
 	if err == nil {
-		t.applyTemplateTransformers(t.main, templ)
+		_, err = t.applyTemplateTransformers(t.main, templ)
 	}
 	return err
 }
@@ -390,6 +399,7 @@ func (t *templateHandler) LookupLayout(d layouts.LayoutDescriptor, f output.Form
 		t.layoutTemplateCacheMu.RUnlock()
 		return cacheVal.templ, cacheVal.found, cacheVal.err
 	}
+
 	t.layoutTemplateCacheMu.RUnlock()
 
 	t.layoutTemplateCacheMu.Lock()
@@ -497,13 +507,15 @@ func (t *templateHandler) findLayout(d layouts.LayoutDescriptor, f output.Format
 			return nil, false, err
 		}
 
-		ts := newTemplateState(templ, overlay, identity.Or(base, overlay))
+		ts := newTemplateState(nil, templ, overlay, identity.Or(base, overlay))
 
 		if found {
 			ts.baseInfo = base
 		}
 
-		t.applyTemplateTransformers(t.main, ts)
+		if _, err := t.applyTemplateTransformers(t.main, ts); err != nil {
+			return nil, false, err
+		}
 
 		if err := t.extractPartials(ts.Template); err != nil {
 			return nil, false, err
@@ -674,7 +686,10 @@ func (t *templateHandler) addTemplateFile(name string, fim hugofs.FileMetaInfo)
 	if err != nil {
 		return tinfo.errWithFileContext("parse failed", err)
 	}
-	t.applyTemplateTransformers(t.main, templ)
+
+	if _, err = t.applyTemplateTransformers(t.main, templ); err != nil {
+		return tinfo.errWithFileContext("transform failed", err)
+	}
 
 	return nil
 }
@@ -745,6 +760,12 @@ func (t *templateHandler) applyTemplateTransformers(ns *templateNamespace, ts *t
 		t.transformNotFound[k] = ts
 	}
 
+	for k, v := range c.deferNodes {
+		if err = t.main.addDeferredTemplate(ts, k, v); err != nil {
+			return nil, err
+		}
+	}
+
 	return c, err
 }
 
@@ -858,7 +879,7 @@ func (t *templateHandler) extractPartials(templ tpl.Template) error {
 			continue
 		}
 
-		ts := newTemplateState(templ, templateInfo{name: templ.Name()}, nil)
+		ts := newTemplateState(nil, templ, templateInfo{name: templ.Name()}, nil)
 		ts.typ = templatePartial
 
 		t.main.mu.RLock()
@@ -954,18 +975,18 @@ type templateNamespace struct {
 	*templateStateMap
 }
 
-func (t templateNamespace) Clone() *templateNamespace {
-	t.mu.Lock()
-	defer t.mu.Unlock()
-
-	t.templateStateMap = &templateStateMap{
-		templates: make(map[string]*templateState),
+func (t *templateNamespace) getPrototypeText() *texttemplate.Template {
+	if t.prototypeTextClone != nil {
+		return t.prototypeTextClone
 	}
+	return t.prototypeText
+}
 
-	t.prototypeText = texttemplate.Must(t.prototypeText.Clone())
-	t.prototypeHTML = htmltemplate.Must(t.prototypeHTML.Clone())
-
-	return &t
+func (t *templateNamespace) getPrototypeHTML() *htmltemplate.Template {
+	if t.prototypeHTMLClone != nil {
+		return t.prototypeHTMLClone
+	}
+	return t.prototypeHTML
 }
 
 func (t *templateNamespace) Lookup(name string) (tpl.Template, bool) {
@@ -996,12 +1017,46 @@ func (t *templateNamespace) newTemplateLookup(in *templateState) func(name strin
 			return templ
 		}
 		if templ, found := findTemplateIn(name, in); found {
-			return newTemplateState(templ, templateInfo{name: templ.Name()}, nil)
+			return newTemplateState(nil, templ, templateInfo{name: templ.Name()}, nil)
 		}
 		return nil
 	}
 }
 
+func (t *templateNamespace) addDeferredTemplate(owner *templateState, name string, n *parse.ListNode) error {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	if _, found := t.templates[name]; found {
+		return nil
+	}
+
+	var templ tpl.Template
+
+	if owner.isText() {
+		prototype := t.getPrototypeText()
+		tt, err := prototype.New(name).Parse("")
+		if err != nil {
+			return fmt.Errorf("failed to parse empty text template %q: %w", name, err)
+		}
+		tt.Tree.Root = n
+		templ = tt
+	} else {
+		prototype := t.getPrototypeHTML()
+		tt, err := prototype.New(name).Parse("")
+		if err != nil {
+			return fmt.Errorf("failed to parse empty HTML template %q: %w", name, err)
+		}
+		tt.Tree.Root = n
+		templ = tt
+	}
+
+	dts := newTemplateState(owner, templ, templateInfo{name: name}, nil)
+	t.templates[name] = dts
+
+	return nil
+}
+
 func (t *templateNamespace) parse(info templateInfo) (*templateState, error) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
@@ -1014,7 +1069,7 @@ func (t *templateNamespace) parse(info templateInfo) (*templateState, error) {
 			return nil, err
 		}
 
-		ts := newTemplateState(templ, info, nil)
+		ts := newTemplateState(nil, templ, info, nil)
 
 		t.templates[info.name] = ts
 
@@ -1028,7 +1083,7 @@ func (t *templateNamespace) parse(info templateInfo) (*templateState, error) {
 		return nil, err
 	}
 
-	ts := newTemplateState(templ, info, nil)
+	ts := newTemplateState(nil, templ, info, nil)
 
 	t.templates[info.name] = ts
 
@@ -1040,6 +1095,9 @@ var _ tpl.IsInternalTemplateProvider = (*templateState)(nil)
 type templateState struct {
 	tpl.Template
 
+	// Set for deferred templates.
+	owner *templateState
+
 	typ       templateType
 	parseInfo tpl.ParseInfo
 	id        identity.Identity
diff --git a/tpl/tplimpl/template_ast_transformers.go b/tpl/tplimpl/template_ast_transformers.go
index 92558a903..ab6cf7b07 100644
--- a/tpl/tplimpl/template_ast_transformers.go
+++ b/tpl/tplimpl/template_ast_transformers.go
@@ -17,6 +17,7 @@ import (
 	"errors"
 	"fmt"
 
+	"github.com/gohugoio/hugo/helpers"
 	htmltemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/htmltemplate"
 	texttemplate "github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate"
 
@@ -38,6 +39,7 @@ const (
 type templateContext struct {
 	visited          map[string]bool
 	templateNotFound map[string]bool
+	deferNodes       map[string]*parse.ListNode
 	lookupFn         func(name string) *templateState
 
 	// The last error encountered.
@@ -77,6 +79,7 @@ func newTemplateContext(
 		lookupFn:         lookupFn,
 		visited:          make(map[string]bool),
 		templateNotFound: make(map[string]bool),
+		deferNodes:       make(map[string]*parse.ListNode),
 	}
 }
 
@@ -116,9 +119,14 @@ const (
 	// "range" over a one-element slice so we can shift dot to the
 	// partial's argument, Arg, while allowing Arg to be falsy.
 	partialReturnWrapperTempl = `{{ $_hugo_dot := $ }}{{ $ := .Arg }}{{ range (slice .Arg) }}{{ $_hugo_dot.Set ("PLACEHOLDER") }}{{ end }}`
+
+	doDeferTempl = `{{ doDefer ("PLACEHOLDER1") ("PLACEHOLDER2") }}`
 )
 
-var partialReturnWrapper *parse.ListNode
+var (
+	partialReturnWrapper *parse.ListNode
+	doDefer              *parse.ListNode
+)
 
 func init() {
 	templ, err := texttemplate.New("").Parse(partialReturnWrapperTempl)
@@ -126,6 +134,12 @@ func init() {
 		panic(err)
 	}
 	partialReturnWrapper = templ.Tree.Root
+
+	templ, err = texttemplate.New("").Funcs(texttemplate.FuncMap{"doDefer": func(string, string) string { return "" }}).Parse(doDeferTempl)
+	if err != nil {
+		panic(err)
+	}
+	doDefer = templ.Tree.Root
 }
 
 // wrapInPartialReturnWrapper copies and modifies the parsed nodes of a
@@ -158,6 +172,7 @@ func (c *templateContext) applyTransformations(n parse.Node) (bool, error) {
 	case *parse.IfNode:
 		c.applyTransformationsToNodes(x.Pipe, x.List, x.ElseList)
 	case *parse.WithNode:
+		c.handleDefer(x)
 		c.applyTransformationsToNodes(x.Pipe, x.List, x.ElseList)
 	case *parse.RangeNode:
 		c.applyTransformationsToNodes(x.Pipe, x.List, x.ElseList)
@@ -191,6 +206,58 @@ func (c *templateContext) applyTransformations(n parse.Node) (bool, error) {
 	return true, c.err
 }
 
+func (c *templateContext) handleDefer(withNode *parse.WithNode) {
+	if len(withNode.Pipe.Cmds) != 1 {
+		return
+	}
+	cmd := withNode.Pipe.Cmds[0]
+	if len(cmd.Args) != 1 {
+		return
+	}
+	idArg := cmd.Args[0]
+
+	p, ok := idArg.(*parse.PipeNode)
+	if !ok {
+		return
+	}
+
+	if len(p.Cmds) != 1 {
+		return
+	}
+
+	cmd = p.Cmds[0]
+
+	if len(cmd.Args) != 2 {
+		return
+	}
+
+	idArg = cmd.Args[0]
+
+	id, ok := idArg.(*parse.ChainNode)
+	if !ok || len(id.Field) != 1 || id.Field[0] != "Defer" {
+		return
+	}
+	if id2, ok := id.Node.(*parse.IdentifierNode); !ok || id2.Ident != "templates" {
+		return
+	}
+
+	deferArg := cmd.Args[1]
+	cmd.Args = []parse.Node{idArg}
+
+	l := doDefer.CopyList()
+	n := l.Nodes[0].(*parse.ActionNode)
+
+	inner := withNode.List.CopyList()
+	innerHash := helpers.MD5String(inner.String())
+	deferredID := tpl.HugoDeferredTemplatePrefix + innerHash
+
+	c.deferNodes[deferredID] = inner
+	withNode.List = l
+
+	n.Pipe.Cmds[0].Args[1].(*parse.PipeNode).Cmds[0].Args[0].(*parse.StringNode).Text = deferredID
+	n.Pipe.Cmds[0].Args[2] = deferArg
+}
+
 func (c *templateContext) applyTransformationsToNodes(nodes ...parse.Node) {
 	for _, node := range nodes {
 		c.applyTransformations(node)
diff --git a/tpl/tplimpl/template_ast_transformers_test.go b/tpl/tplimpl/template_ast_transformers_test.go
index bd889b832..630415dac 100644
--- a/tpl/tplimpl/template_ast_transformers_test.go
+++ b/tpl/tplimpl/template_ast_transformers_test.go
@@ -47,7 +47,7 @@ func TestTransformRecursiveTemplate(t *testing.T) {
 }
 
 func newTestTemplate(templ tpl.Template) *templateState {
-	return newTemplateState(
+	return newTemplateState(nil,
 		templ,
 		templateInfo{
 			name: templ.Name(),