Add multilingual multihost support

This commit adds multihost support when more than one language is configured and `baseURL` is set per language.

Updates #4027

8 files changed, 162 insertions, 33 deletions

diff --git a/hugolib/config.go b/hugolib/config.go
index acfa0704d..db59253cd 100644
--- a/hugolib/config.go
+++ b/hugolib/config.go
@@ -19,6 +19,7 @@ import (
 	"io"
 	"strings"
 
+	"github.com/gohugoio/hugo/config"
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/spf13/afero"
 	"github.com/spf13/viper"
@@ -80,11 +81,34 @@ func LoadConfig(fs afero.Fs, relativeSourcePath, configFilename string) (*viper.
 		helpers.Deprecated("site config", "disableRobotsTXT", "Use disableKinds= [\"robotsTXT\"]", false)
 	}
 
-	loadDefaultSettingsFor(v)
+	if err := loadDefaultSettingsFor(v); err != nil {
+		return v, err
+	}
 
 	return v, nil
 }
 
+func loadLanguageSettings(cfg config.Provider) error {
+	multilingual := cfg.GetStringMap("languages")
+	var (
+		langs helpers.Languages
+		err   error
+	)
+
+	if len(multilingual) == 0 {
+		langs = append(langs, helpers.NewDefaultLanguage(cfg))
+	} else {
+		langs, err = toSortedLanguages(cfg, multilingual)
+		if err != nil {
+			return fmt.Errorf("Failed to parse multilingual config: %s", err)
+		}
+	}
+
+	cfg.Set("languagesSorted", langs)
+
+	return nil
+}
+
 func loadDefaultSettingsFor(v *viper.Viper) error {
 
 	c, err := helpers.NewContentSpec(v)
@@ -154,5 +178,5 @@ func loadDefaultSettingsFor(v *viper.Viper) error {
 	v.SetDefault("debug", false)
 	v.SetDefault("disableFastRender", false)
 
-	return nil
+	return loadLanguageSettings(v)
 }
diff --git a/hugolib/hugo_sites.go b/hugolib/hugo_sites.go
index 6e2340903..e0697507b 100644
--- a/hugolib/hugo_sites.go
+++ b/hugolib/hugo_sites.go
@@ -15,7 +15,6 @@ package hugolib
 
 import (
 	"errors"
-	"fmt"
 	"strings"
 	"sync"
 
@@ -37,9 +36,16 @@ type HugoSites struct {
 
 	multilingual *Multilingual
 
+	// Multihost is set if multilingual and baseURL set on the language level.
+	multihost bool
+
 	*deps.Deps
 }
 
+func (h *HugoSites) IsMultihost() bool {
+	return h != nil && h.multihost
+}
+
 // GetContentPage finds a Page with content given the absolute filename.
 // Returns nil if none found.
 func (h *HugoSites) GetContentPage(filename string) *Page {
@@ -92,6 +98,31 @@ func newHugoSites(cfg deps.DepsCfg, sites ...*Site) (*HugoSites, error) {
 
 	h.Deps = sites[0].Deps
 
+	// The baseURL may be provided at the language level. If that is true,
+	// then every language must have a baseURL. In this case we always render
+	// to a language sub folder, which is then stripped from all the Permalink URLs etc.
+	var baseURLFromLang bool
+
+	for _, s := range sites {
+		burl := s.Language.GetLocal("baseURL")
+		if baseURLFromLang && burl == nil {
+			return h, errors.New("baseURL must be set on all or none of the languages")
+		}
+
+		if burl != nil {
+			baseURLFromLang = true
+		}
+	}
+
+	if baseURLFromLang {
+		for _, s := range sites {
+			// TODO(bep) multihost check
+			s.Info.defaultContentLanguageInSubdir = true
+			s.Cfg.Set("defaultContentLanguageInSubdir", true)
+		}
+		h.multihost = true
+	}
+
 	return h, nil
 }
 
@@ -180,39 +211,19 @@ func createSitesFromConfig(cfg deps.DepsCfg) ([]*Site, error) {
 		sites []*Site
 	)
 
-	multilingual := cfg.Cfg.GetStringMap("languages")
-
-	if len(multilingual) == 0 {
-		l := helpers.NewDefaultLanguage(cfg.Cfg)
-		cfg.Language = l
-		s, err := newSite(cfg)
-		if err != nil {
-			return nil, err
-		}
-		sites = append(sites, s)
-	}
+	languages := getLanguages(cfg.Cfg)
 
-	if len(multilingual) > 0 {
+	for _, lang := range languages {
+		var s *Site
 		var err error
-
-		languages, err := toSortedLanguages(cfg.Cfg, multilingual)
+		cfg.Language = lang
+		s, err = newSite(cfg)
 
 		if err != nil {
-			return nil, fmt.Errorf("Failed to parse multilingual config: %s", err)
+			return nil, err
 		}
 
-		for _, lang := range languages {
-			var s *Site
-			var err error
-			cfg.Language = lang
-			s, err = newSite(cfg)
-
-			if err != nil {
-				return nil, err
-			}
-
-			sites = append(sites, s)
-		}
+		sites = append(sites, s)
 	}
 
 	return sites, nil
@@ -227,7 +238,12 @@ func (h *HugoSites) reset() {
 
 func (h *HugoSites) createSitesFromConfig() error {
 
+	if err := loadLanguageSettings(h.Cfg); err != nil {
+		return err
+	}
+
 	depsCfg := deps.DepsCfg{Fs: h.Fs, Cfg: h.Cfg}
+
 	sites, err := createSitesFromConfig(depsCfg)
 
 	if err != nil {
@@ -286,7 +302,7 @@ type BuildCfg struct {
 
 func (h *HugoSites) renderCrossSitesArtifacts() error {
 
-	if !h.multilingual.enabled() {
+	if !h.multilingual.enabled() || h.IsMultihost() {
 		return nil
 	}
 
diff --git a/hugolib/hugo_sites_build_test.go b/hugolib/hugo_sites_build_test.go
index 96e2c66b2..079f0fcfa 100644
--- a/hugolib/hugo_sites_build_test.go
+++ b/hugolib/hugo_sites_build_test.go
@@ -1269,7 +1269,7 @@ lag:
 		t.Fatalf("Failed to create sites: %s", err)
 	}
 
-	if len(sites.Sites) != 4 {
+	if len(sites.Sites) == 0 {
 		t.Fatalf("Got %d sites", len(sites.Sites))
 	}
 
diff --git a/hugolib/hugo_sites_multihost_test.go b/hugolib/hugo_sites_multihost_test.go
new file mode 100644
index 000000000..864d52c71
--- /dev/null
+++ b/hugolib/hugo_sites_multihost_test.go
@@ -0,0 +1,72 @@
+package hugolib
+
+import (
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMultihosts(t *testing.T) {
+	t.Parallel()
+
+	var multiSiteTOMLConfigTemplate = `
+paginate = 1
+disablePathToLower = true
+defaultContentLanguage = "{{ .DefaultContentLanguage }}"
+defaultContentLanguageInSubdir = {{ .DefaultContentLanguageInSubdir }}
+
+[permalinks]
+other = "/somewhere/else/:filename"
+
+[Taxonomies]
+tag = "tags"
+
+[Languages]
+[Languages.en]
+baseURL = "https://example.com"
+weight = 10
+title = "In English"
+languageName = "English"
+
+[Languages.fr]
+baseURL = "https://example.fr"
+weight = 20
+title = "Le Français"
+languageName = "Français"
+
+[Languages.nn]
+baseURL = "https://example.no"
+weight = 30
+title = "På nynorsk"
+languageName = "Nynorsk"
+
+`
+
+	siteConfig := testSiteConfig{Fs: afero.NewMemMapFs(), DefaultContentLanguage: "fr", DefaultContentLanguageInSubdir: false}
+	sites := createMultiTestSites(t, siteConfig, multiSiteTOMLConfigTemplate)
+	fs := sites.Fs
+	cfg := BuildCfg{Watching: true}
+	th := testHelper{sites.Cfg, fs, t}
+	assert := require.New(t)
+
+	err := sites.Build(cfg)
+	assert.NoError(err)
+
+	th.assertFileContent("public/en/sect/doc1-slug/index.html", "Hello")
+
+	s1 := sites.Sites[0]
+
+	s1h := s1.getPage(KindHome)
+	assert.True(s1h.IsTranslated())
+	assert.Len(s1h.Translations(), 2)
+	assert.Equal("https://example.com/", s1h.Permalink())
+
+	s2 := sites.Sites[1]
+	s2h := s2.getPage(KindHome)
+	assert.Equal("https://example.fr/", s2h.Permalink())
+
+	th.assertFileContentStraight("public/fr/index.html", "French Home Page")
+	th.assertFileContentStraight("public/en/index.html", "Default Home Page")
+
+}
diff --git a/hugolib/multilingual.go b/hugolib/multilingual.go
index e0245fa2b..589df66e0 100644
--- a/hugolib/multilingual.go
+++ b/hugolib/multilingual.go
@@ -47,6 +47,14 @@ func (ml *Multilingual) Language(lang string) *helpers.Language {
 	return ml.langMap[lang]
 }
 
+func getLanguages(cfg config.Provider) helpers.Languages {
+	if cfg.IsSet("languagesSorted") {
+		return cfg.Get("languagesSorted").(helpers.Languages)
+	}
+
+	return helpers.Languages{helpers.NewDefaultLanguage(cfg)}
+}
+
 func newMultiLingualFromSites(cfg config.Provider, sites ...*Site) (*Multilingual, error) {
 	languages := make(helpers.Languages, len(sites))
 
diff --git a/hugolib/page.go b/hugolib/page.go
index d928b92f9..7da77f192 100644
--- a/hugolib/page.go
+++ b/hugolib/page.go
@@ -1754,6 +1754,11 @@ func (p *Page) shouldAddLanguagePrefix() bool {
 		return false
 	}
 
+	if p.s.owner.IsMultihost() {
+		// TODO(bep) multihost check vs lang below
+		return true
+	}
+
 	if p.Lang() == "" {
 		return false
 	}
diff --git a/hugolib/page_paths.go b/hugolib/page_paths.go
index e18e0f10e..993ad0780 100644
--- a/hugolib/page_paths.go
+++ b/hugolib/page_paths.go
@@ -257,6 +257,10 @@ func (p *Page) createRelativePermalinkForOutputFormat(f output.Format) string {
 		tp = strings.TrimSuffix(tp, f.BaseFilename())
 	}
 
+	if p.s.owner.IsMultihost() {
+		tp = strings.TrimPrefix(tp, helpers.FilePathSeparator+p.s.Info.Language.Lang)
+	}
+
 	return p.s.PathSpec.URLizeFilename(tp)
 }
 
diff --git a/hugolib/site_render.go b/hugolib/site_render.go
index 4118f3eef..b4d688bda 100644
--- a/hugolib/site_render.go
+++ b/hugolib/site_render.go
@@ -387,7 +387,7 @@ func (s *Site) renderAliases() error {
 		}
 	}
 
-	if s.owner.multilingual.enabled() {
+	if s.owner.multilingual.enabled() && !s.owner.IsMultihost() {
 		mainLang := s.owner.multilingual.DefaultLang
 		if s.Info.defaultContentLanguageInSubdir {
 			mainLangURL := s.PathSpec.AbsURL(mainLang.Lang, false)