Fix auto-creation of root sections in multilingual sites

Fixes #14681

Co-authored-by: Joe Mooring <joe@mooring.com>

hugolib/content_map_page_assembler.go

@@ -497,14 +497,14 @@ func (a *allPagesAssembler) doCreatePages(prefix string, depth int) error {
 
 		isTaxonomy := !a.h.getFirstTaxonomyConfig(s).IsZero()
 		isRootSection := !isTaxonomy && level == 1 && cnh.isBranchNode(n)
-
-		if isRootSection {
-			// This is a root section.
-			a.seenRootSections.SetIfAbsent(cnh.PathInfo(n).Section(), true)
-		} else if !isTaxonomy {
+		if !isTaxonomy {
 			p := cnh.PathInfo(n)
 			rootSection := p.Section()
 			_, err := a.seenRootSections.GetOrCreate(rootSection, func() (bool, error) {
+				if isRootSection {
+					return true, nil
+				}
+
 				// Try to preserve the original casing if possible.
 				sectionUnnormalized := p.Unnormalized().Section()
 				rootSectionPath := a.h.Conf.PathParser().Parse(files.ComponentFolderContent, "/"+sectionUnnormalized+"/_index.md")
@@ -520,6 +520,51 @@ func (a *allPagesAssembler) doCreatePages(prefix string, depth int) error {
 					return true, err
 				}
 				treePages.InsertRaw(rootSectionPath.Base(), rootSectionPages)
+
+				// Collect vectors from descendant pages to create section
+				// pages for all languages that have content in this section.
+				nm, replaced := contentNodeToContentNodesPage(rootSectionPages)
+				if replaced {
+					treePages.InsertRaw(rootSectionPath.Base(), nm)
+				}
+				missingVectors := sitesmatrix.Vectors{}
+				pw.WalkContext.AddEventListener("sitesmatrix", rootSectionPath.Base(),
+					func(e *doctree.Event[contentNode]) {
+						if cnh.isBranchNode(e.Source) && !a.h.getFirstTaxonomyConfig(e.Path).IsZero() {
+							return
+						}
+						n := e.Source
+						e.StopPropagation()
+						n.forEeachContentNode(
+							func(vec sitesmatrix.Vector, nn contentNode) bool {
+								if _, found := nm[vec]; !found {
+									missingVectors[vec] = struct{}{}
+								}
+								return true
+							})
+					},
+				)
+				pw.WalkContext.HooksPost().Push(
+					func() error {
+						if len(missingVectors) > 0 {
+							vec := missingVectors.VectorSample()
+							nm[vec] = &pageMetaSource{
+								pathInfo:            rootSectionPath,
+								sitesMatrixBase:     missingVectors,
+								sitesMatrixBaseOnly: true,
+								pageConfigSource: &pagemeta.PageConfigEarly{
+									Kind: kinds.KindSection,
+								},
+							}
+							_, _, err := transformPages(rootSectionPath.Base(), nm, cascades)
+							if err != nil {
+								return err
+							}
+						}
+						return nil
+					},
+				)
+
 				return true, nil
 			})
 			if err != nil {

hugolib/language_content_dir_test.go

@@ -171,6 +171,65 @@ title: "p4 theme (nl)"
 	b.AssertFileContent("public/en/index.html", `home (en): en: p1 (en)|p2 (en)|p3 (en)|:END`)
 }
 
+// Issue 14681
+func TestPublishMultilingualSectionCreation(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+capitalizeListTitles = false
+pluralizeListTitles = false
+disableKinds = ['rss','sitemap','taxonomy','term']
+
+defaultContentLanguage = "fr"
+defaultContentLanguageInSubdir = true
+
+[languages.fr]
+contentDir = "content/fr"
+weight = 1
+
+[languages.en]
+contentDir = "content/en"
+weight = 2
+
+[languages.de]
+contentDir = "content/de"
+weight = 3
+-- layouts/home.html --
+HOME {{ .Language.Name }}
+-- layouts/page.html --
+{{ .Title }} {{ .Language.Name }}
+-- layouts/section.html --
+{{ .Title }} {{ .Language.Name }}
+-- content/de/s1/p1.md --
+---
+title: p1
+---
+-- content/en/s1/p2.md --
+---
+title: p2
+---
+-- content/fr/s1/p3.md --
+---
+title: p3
+---
+`
+
+	b := Test(t, files)
+
+	b.AssertFileContent("public/de/index.html", "HOME de")
+	b.AssertFileContent("public/de/s1/index.html", "s1 de")
+	b.AssertFileContent("public/de/s1/p1/index.html", "p1 de")
+
+	b.AssertFileContent("public/en/index.html", "HOME en")
+	b.AssertFileContent("public/en/s1/index.html", "s1 en") // fail (file does not exist)
+	b.AssertFileContent("public/en/s1/p2/index.html", "p2 en")
+
+	b.AssertFileContent("public/fr/index.html", "HOME fr")
+	b.AssertFileContent("public/fr/s1/index.html", "s1 fr") // fail (file does not exist)
+	b.AssertFileContent("public/fr/s1/p3/index.html", "p3 fr")
+}
+
 // Issue 13993
 func TestIssue13993(t *testing.T) {
 	t.Parallel()