Add js.Batch

Fixes #12626
Closes #7499
Closes #9978
Closes #12879
Closes #13113
Fixes #13116

8 files changed, 83 insertions, 20 deletions

diff --git a/tpl/debug/debug.go b/tpl/debug/debug.go
index ae1acf5eb..fd676f0e2 100644
--- a/tpl/debug/debug.go
+++ b/tpl/debug/debug.go
@@ -41,7 +41,7 @@ func New(d *deps.Deps) *Namespace {
 
 	l := d.Log.InfoCommand("timer")
 
-	d.BuildEndListeners.Add(func() {
+	d.BuildEndListeners.Add(func(...any) bool {
 		type data struct {
 			Name     string
 			Count    int
@@ -84,6 +84,8 @@ func New(d *deps.Deps) *Namespace {
 		}
 
 		ns.timers = make(map[string][]*timer)
+
+		return false
 	})
 
 	return ns
diff --git a/tpl/fmt/fmt.go b/tpl/fmt/fmt.go
index e9c18360a..264cb1435 100644
--- a/tpl/fmt/fmt.go
+++ b/tpl/fmt/fmt.go
@@ -30,8 +30,9 @@ func New(d *deps.Deps) *Namespace {
 		logger: d.Log,
 	}
 
-	d.BuildStartListeners.Add(func() {
+	d.BuildStartListeners.Add(func(...any) bool {
 		ns.logger.Reset()
+		return false
 	})
 
 	return ns
diff --git a/tpl/js/init.go b/tpl/js/init.go
index 69d7c7275..97e76c33d 100644
--- a/tpl/js/init.go
+++ b/tpl/js/init.go
@@ -24,7 +24,10 @@ const name = "js"
 
 func init() {
 	f := func(d *deps.Deps) *internal.TemplateFuncsNamespace {
-		ctx := New(d)
+		ctx, err := New(d)
+		if err != nil {
+			panic(err)
+		}
 
 		ns := &internal.TemplateFuncsNamespace{
 			Name:    name,
diff --git a/tpl/js/js.go b/tpl/js/js.go
index c68e0af92..b686b76a7 100644
--- a/tpl/js/js.go
+++ b/tpl/js/js.go
@@ -1,4 +1,4 @@
-// Copyright 2020 The Hugo Authors. All rights reserved.
+// 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.
@@ -17,29 +17,47 @@ package js
 import (
 	"errors"
 
+	"github.com/gohugoio/hugo/common/maps"
 	"github.com/gohugoio/hugo/deps"
+	"github.com/gohugoio/hugo/internal/js/esbuild"
 	"github.com/gohugoio/hugo/resources"
 	"github.com/gohugoio/hugo/resources/resource"
+	"github.com/gohugoio/hugo/resources/resource_factories/create"
 	"github.com/gohugoio/hugo/resources/resource_transformers/babel"
-	"github.com/gohugoio/hugo/resources/resource_transformers/js"
+	jstransform "github.com/gohugoio/hugo/resources/resource_transformers/js"
 	"github.com/gohugoio/hugo/tpl/internal/resourcehelpers"
 )
 
 // New returns a new instance of the js-namespaced template functions.
-func New(deps *deps.Deps) *Namespace {
-	if deps.ResourceSpec == nil {
-		return &Namespace{}
+func New(d *deps.Deps) (*Namespace, error) {
+	if d.ResourceSpec == nil {
+		return &Namespace{}, nil
 	}
-	return &Namespace{
-		client:      js.New(deps.BaseFs.Assets, deps.ResourceSpec),
-		babelClient: babel.New(deps.ResourceSpec),
+
+	batcherClient, err := esbuild.NewBatcherClient(d)
+	if err != nil {
+		return nil, err
 	}
+
+	return &Namespace{
+		d:                 d,
+		jsTransformClient: jstransform.New(d.BaseFs.Assets, d.ResourceSpec),
+		jsBatcherClient:   batcherClient,
+		jsBatcherStore:    maps.NewCache[string, esbuild.Batcher](),
+		createClient:      create.New(d.ResourceSpec),
+		babelClient:       babel.New(d.ResourceSpec),
+	}, nil
 }
 
 // Namespace provides template functions for the "js" namespace.
 type Namespace struct {
-	client      *js.Client
-	babelClient *babel.Client
+	d *deps.Deps
+
+	jsTransformClient *jstransform.Client
+	createClient      *create.Client
+	babelClient       *babel.Client
+	jsBatcherClient   *esbuild.BatcherClient
+	jsBatcherStore    *maps.Cache[string, esbuild.Batcher]
 }
 
 // Build processes the given Resource with ESBuild.
@@ -65,7 +83,24 @@ func (ns *Namespace) Build(args ...any) (resource.Resource, error) {
 		m = map[string]any{"targetPath": targetPath}
 	}
 
-	return ns.client.Process(r, m)
+	return ns.jsTransformClient.Process(r, m)
+}
+
+// Batch creates a new Batcher with the given ID.
+// Repeated calls with the same ID will return the same Batcher.
+// The ID will be used to name the root directory of the batch.
+// Forward slashes in the ID is allowed.
+func (ns *Namespace) Batch(id string) (esbuild.Batcher, error) {
+	if err := esbuild.ValidateBatchID(id, true); err != nil {
+		return nil, err
+	}
+	b, err := ns.jsBatcherStore.GetOrCreate(id, func() (esbuild.Batcher, error) {
+		return ns.jsBatcherClient.New(id)
+	})
+	if err != nil {
+		return nil, err
+	}
+	return b, nil
 }
 
 // Babel processes the given Resource with Babel.
diff --git a/tpl/partials/partials.go b/tpl/partials/partials.go
index 8de312fd8..4441b5fa5 100644
--- a/tpl/partials/partials.go
+++ b/tpl/partials/partials.go
@@ -81,8 +81,9 @@ func New(deps *deps.Deps) *Namespace {
 
 	cache := &partialCache{cache: lru}
 	deps.BuildStartListeners.Add(
-		func() {
+		func(...any) bool {
 			cache.clear()
+			return false
 		})
 
 	return &Namespace{
diff --git a/tpl/tplimpl/embedded/templates/_hugo/build/js/batch-esm-runner.gotmpl b/tpl/tplimpl/embedded/templates/_hugo/build/js/batch-esm-runner.gotmpl
new file mode 100644
index 000000000..e1b3b9bc3
--- /dev/null
+++ b/tpl/tplimpl/embedded/templates/_hugo/build/js/batch-esm-runner.gotmpl
@@ -0,0 +1,16 @@
+{{ range $i, $e := .Scripts -}}
+  {{ printf "import { %s as Script%d } from %q;" .Export $i .Import }}
+{{ end -}}
+{{ range $i, $e := .Runners }}
+  {{ printf "import { %s as Run%d } from %q;" .Export $i .Import }}
+{{ end }}
+{{/*  */}}
+let scripts = [];
+{{ range $i, $e := .Scripts -}}
+  scripts.push({{ .RunnerJSON $i }});
+{{ end -}}
+{{/*  */}}
+{{ range $i, $e := .Runners }}
+  {{ $id := printf "Run%d" $i }}
+  {{ $id }}(scripts);
+{{ end }}
diff --git a/tpl/tplimpl/template.go b/tpl/tplimpl/template.go
index fd07db68e..9e2af046d 100644
--- a/tpl/tplimpl/template.go
+++ b/tpl/tplimpl/template.go
@@ -695,13 +695,13 @@ func (t *templateHandler) applyBaseTemplate(overlay, base templateInfo) (tpl.Tem
 		if !base.IsZero() {
 			templ, err = templ.Parse(base.template)
 			if err != nil {
-				return nil, base.errWithFileContext("parse failed", err)
+				return nil, base.errWithFileContext("text: base: parse failed", err)
 			}
 		}
 
 		templ, err = texttemplate.Must(templ.Clone()).Parse(overlay.template)
 		if err != nil {
-			return nil, overlay.errWithFileContext("parse failed", err)
+			return nil, overlay.errWithFileContext("text: overlay: parse failed", err)
 		}
 
 		// The extra lookup is a workaround, see
@@ -720,13 +720,13 @@ func (t *templateHandler) applyBaseTemplate(overlay, base templateInfo) (tpl.Tem
 	if !base.IsZero() {
 		templ, err = templ.Parse(base.template)
 		if err != nil {
-			return nil, base.errWithFileContext("parse failed", err)
+			return nil, base.errWithFileContext("html: base: parse failed", err)
 		}
 	}
 
 	templ, err = htmltemplate.Must(templ.Clone()).Parse(overlay.template)
 	if err != nil {
-		return nil, overlay.errWithFileContext("parse failed", err)
+		return nil, overlay.errWithFileContext("html: overlay: parse failed", err)
 	}
 
 	// The extra lookup is a workaround, see
diff --git a/tpl/tplimpl/template_funcs.go b/tpl/tplimpl/template_funcs.go
index 3daba74a0..d73d4d336 100644
--- a/tpl/tplimpl/template_funcs.go
+++ b/tpl/tplimpl/template_funcs.go
@@ -251,6 +251,9 @@ func newTemplateExecuter(d *deps.Deps) (texttemplate.Executer, map[string]reflec
 }
 
 func createFuncMap(d *deps.Deps) map[string]any {
+	if d.TmplFuncMap != nil {
+		return d.TmplFuncMap
+	}
 	funcMap := template.FuncMap{}
 
 	nsMap := make(map[string]any)
@@ -292,5 +295,7 @@ func createFuncMap(d *deps.Deps) map[string]any {
 		}
 	}
 
-	return funcMap
+	d.TmplFuncMap = funcMap
+
+	return d.TmplFuncMap
 }