tpl: Fix the case for a shortcode in a nested folder only

Fixes #13605

Author: bep

Diff for: hugolib/shortcode.go

@@ -677,13 +677,7 @@ Loop:
 
 			// Used to check if the template expects inner content,
 			// so just pick one arbitrarily with the same name.
-			q := tplimpl.TemplateQuery{
-				Path:     "",
-				Name:     sc.name,
-				Category: tplimpl.CategoryShortcode,
-				Consider: nil,
-			}
-			templ := s.s.TemplateStore.LookupShortcode(q)
+			templ := s.s.TemplateStore.LookupShortcodeByName(sc.name)
 			if templ == nil {
 				return nil, fmt.Errorf("%s: template for shortcode %q not found", errorPrefix, sc.name)
 			}

Diff for: tpl/tplimpl/templatestore.go

@@ -122,6 +122,7 @@ func NewStore(opts StoreOptions, siteOpts SiteOptions) (*TemplateStore, error) {
 		treeMain:            doctree.NewSimpleTree[map[nodeKey]*TemplInfo](),
 		treeShortcodes:      doctree.NewSimpleTree[map[string]map[TemplateDescriptor]*TemplInfo](),
 		templatesByPath:     maps.NewCache[string, *TemplInfo](),
+		shortcodesByName:    maps.NewCache[string, *TemplInfo](),
 		cacheLookupPartials: maps.NewCache[string, *TemplInfo](),
 
 		// Note that the funcs passed below is just for name validation.
@@ -419,9 +420,10 @@ type TemplateStore struct {
 	siteOpts   SiteOptions
 	htmlFormat output.Format
 
-	treeMain        *doctree.SimpleTree[map[nodeKey]*TemplInfo]
-	treeShortcodes  *doctree.SimpleTree[map[string]map[TemplateDescriptor]*TemplInfo]
-	templatesByPath *maps.Cache[string, *TemplInfo]
+	treeMain         *doctree.SimpleTree[map[nodeKey]*TemplInfo]
+	treeShortcodes   *doctree.SimpleTree[map[string]map[TemplateDescriptor]*TemplInfo]
+	templatesByPath  *maps.Cache[string, *TemplInfo]
+	shortcodesByName *maps.Cache[string, *TemplInfo]
 
 	dh descriptorHandler
 
@@ -576,6 +578,15 @@ func (s *TemplateStore) LookupPartial(pth string) *TemplInfo {
 	return ti
 }
 
+func (s *TemplateStore) LookupShortcodeByName(name string) *TemplInfo {
+	name = strings.ToLower(name)
+	ti, _ := s.shortcodesByName.Get(name)
+	if ti == nil {
+		return nil
+	}
+	return ti
+}
+
 func (s *TemplateStore) LookupShortcode(q TemplateQuery) *TemplInfo {
 	q.init()
 	k1 := s.key(q.Path)
@@ -1039,6 +1050,7 @@ func (s *TemplateStore) insertShortcode(pi *paths.Path, fi hugofs.FileMetaInfo,
 
 	m1[d] = ti
 
+	s.shortcodesByName.Set(k2, ti)
 	s.setTemplateByPath(pi.Path(), ti)
 
 	if fi != nil {

Diff for: tpl/tplimpl/templatestore_integration_test.go

@@ -1127,6 +1127,28 @@ single.html
 	b.AssertFileContent("public/s3/index.html", "single.html") // fail
 }
 
+func TestIssue13605(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['home','rss','section','sitemap','taxonomy','term']
+-- content/s1/p1.md --
+---
+title: p1
+---
+{{< sc >}}
+-- layouts/s1/_shortcodes/sc.html --
+layouts/s1/_shortcodes/sc.html
+-- layouts/single.html --
+{{ .Content }}
+`
+
+	b := hugolib.Test(t, files)
+
+	b.AssertFileContent("public/s1/p1/index.html", "layouts/s1/_shortcodes/sc.html")
+}
+
 func TestSkipDotFiles(t *testing.T) {
 	t.Parallel()