A proof-of-concept patch to illustrate the proposed feature

hugo-github-issue-8279.patch

From 666e8b2ce0a000168ee5de0e5b98147e462dab79 Mon Sep 17 00:00:00 2001
From: Robert Schulze <robert@dotless.de>
Date: Tue, 2 Nov 2021 14:38:57 +0100
Subject: [PATCH] --wip-- [skip ci]

---
 hugolib/paths/paths.go |  5 +++++
 hugolib/site.go        | 30 +++++++++++++++++++++++++-----
 hugolib/site_render.go |  8 +++++++-
 langs/config.go        |  2 ++
 langs/language.go      |  1 +
 5 files changed, 40 insertions(+), 6 deletions(-)

diff --git hugolib/paths/paths.go hugolib/paths/paths.go
index 1ab7ae87..8f6be8eb 100644
--- hugolib/paths/paths.go
+++ hugolib/paths/paths.go
@@ -231,6 +231,11 @@ func (p *Paths) GetLanguagePrefix() string {
 	if currentLang == "" || (currentLang == defaultLang && !defaultInSubDir) {
 		return ""
 	}
+
+	if p.Language.LanguagePrefix != "" {
+		return p.Language.LanguagePrefix
+	}
+
 	return currentLang
 }
 
diff --git hugolib/site.go hugolib/site.go
index 96cf0b93..0ea05869 100644
--- hugolib/site.go
+++ hugolib/site.go
@@ -1277,7 +1277,11 @@ func (s *Site) initialize() (err error) {
 func (s *SiteInfo) HomeAbsURL() string {
 	base := ""
 	if s.IsMultiLingual() {
-		base = s.Language().Lang
+		if s.Language().LanguagePrefix != "" {
+			base = s.Language().LanguagePrefix
+		} else {
+			base = s.Language().Lang
+		}
 	}
 	return s.owner.AbsURL(base, false)
 }
@@ -1309,7 +1313,11 @@ func (s *Site) initializeSiteInfo() error {
 
 	languagePrefix := ""
 	if s.multilingualEnabled() && (defaultContentInSubDir || lang.Lang != defaultContentLanguage) {
-		languagePrefix = "/" + lang.Lang
+		if lang.LanguagePrefix != "" {
+			languagePrefix = "/" + lang.LanguagePrefix
+		} else {
+			languagePrefix = "/" + lang.Lang
+		}
 	}
 
 	uglyURLs := func(p page.Page) bool {
@@ -1544,7 +1552,11 @@ func (s *Site) assembleMenus() {
 // get any language code to prefix the target file path with.
 func (s *Site) getLanguageTargetPathLang(alwaysInSubDir bool) string {
 	if s.h.IsMultihost() {
-		return s.Language().Lang
+		if s.Language().LanguagePrefix != "" {
+			return s.Language().LanguagePrefix
+		} else {
+			return s.Language().Lang
+		}
 	}
 
 	return s.getLanguagePermalinkLang(alwaysInSubDir)
@@ -1557,13 +1569,21 @@ func (s *Site) getLanguagePermalinkLang(alwaysInSubDir bool) string {
 	}
 
 	if alwaysInSubDir {
-		return s.Language().Lang
+		if s.Language().LanguagePrefix != "" {
+			return s.Language().LanguagePrefix
+		} else {
+			return s.Language().Lang
+		}
 	}
 
 	isDefault := s.Language().Lang == s.multilingual().DefaultLang.Lang
 
 	if !isDefault || s.Info.defaultContentLanguageInSubdir {
-		return s.Language().Lang
+		if s.Language().LanguagePrefix != "" {
+			return s.Language().LanguagePrefix
+		} else {
+			return s.Language().Lang
+		}
 	}
 
 	return ""
diff --git hugolib/site_render.go hugolib/site_render.go
index 77ece780..e3cd46d5 100644
--- hugolib/site_render.go
+++ hugolib/site_render.go
@@ -388,7 +388,13 @@ func (s *Site) renderMainLanguageRedirect() error {
 	if found {
 		mainLang := s.h.multilingual.DefaultLang
 		if s.Info.defaultContentLanguageInSubdir {
-			mainLangURL := s.PathSpec.AbsURL(mainLang.Lang+"/", false)
+			mainLangPrefix := ""
+			if mainLang.LanguagePrefix != "" {
+				mainLangPrefix = mainLang.LanguagePrefix
+			} else {
+				mainLangPrefix = mainLang.Lang
+			}
+			mainLangURL := s.PathSpec.AbsURL(mainLangPrefix+"/", false)
 			s.Log.Debugf("Write redirect to main language %s: %s", mainLang, mainLangURL)
 			if err := s.publishDestAlias(true, "/", mainLangURL, html, nil); err != nil {
 				return err
diff --git langs/config.go langs/config.go
index f79b7dd0..974b7fea 100644
--- langs/config.go
+++ langs/config.go
@@ -190,6 +190,8 @@ func toSortedLanguages(cfg config.Provider, l map[string]interface{}) (Languages
 				language.LanguageName = cast.ToString(v)
 			case "languagedirection":
 				language.LanguageDirection = cast.ToString(v)
+			case "languageprefix":
+				language.LanguagePrefix = cast.ToString(v)
 			case "weight":
 				language.Weight = cast.ToInt(v)
 			case "contentdir":
diff --git langs/language.go langs/language.go
index c4cba15b..ba0cabd3 100644
--- langs/language.go
+++ langs/language.go
@@ -48,6 +48,7 @@ type Language struct {
 	Lang              string
 	LanguageName      string
 	LanguageDirection string
+	LanguagePrefix    string
 	Title             string
 	Weight            int
 
-- 
2.33.0