output: Support templates per site/language

This applies to both regular templates and shortcodes. So, if the site language is French and the output format is AMP, this is the (start) of the lookup order for the home page:

1. index.fr.amp.html
2. index.amp.html
3. index.fr.html
4. index.html
5. ...

Fixes #3360

7 files changed, 109 insertions, 40 deletions

diff --git a/hugolib/hugo_sites_build_test.go b/hugolib/hugo_sites_build_test.go
index c343f6087..96e2c66b2 100644
--- a/hugolib/hugo_sites_build_test.go
+++ b/hugolib/hugo_sites_build_test.go
@@ -305,12 +305,12 @@ func doTestMultiSitesBuild(t *testing.T, configTemplate, configSuffix string) {
 	require.True(t, strings.Contains(languageRedirect, "0; url=http://example.com/blog/fr"), languageRedirect)
 
 	// check home page content (including data files rendering)
-	th.assertFileContent("public/en/index.html", "Home Page 1", "Hello", "Hugo Rocks!")
-	th.assertFileContent("public/fr/index.html", "Home Page 1", "Bonjour", "Hugo Rocks!")
+	th.assertFileContent("public/en/index.html", "Default Home Page 1", "Hello", "Hugo Rocks!")
+	th.assertFileContent("public/fr/index.html", "French Home Page 1", "Bonjour", "Hugo Rocks!")
 
 	// check single page content
-	th.assertFileContent("public/fr/sect/doc1/index.html", "Single", "Shortcode: Bonjour")
-	th.assertFileContent("public/en/sect/doc1-slug/index.html", "Single", "Shortcode: Hello")
+	th.assertFileContent("public/fr/sect/doc1/index.html", "Single", "Shortcode: Bonjour", "LingoFrench")
+	th.assertFileContent("public/en/sect/doc1-slug/index.html", "Single", "Shortcode: Hello", "LingoDefault")
 
 	// Check node translations
 	homeEn := enSite.getPage(KindHome)
@@ -1042,7 +1042,14 @@ func createMultiTestSitesForConfig(t *testing.T, siteConfig testSiteConfig, conf
 
 	if err := afero.WriteFile(mf,
 		filepath.Join("layouts", "index.html"),
-		[]byte("{{ $p := .Paginator }}Home Page {{ $p.PageNumber }}: {{ .Title }}|{{ .IsHome }}|{{ i18n \"hello\" }}|{{ .Permalink }}|{{  .Site.Data.hugo.slogan }}"),
+		[]byte("{{ $p := .Paginator }}Default Home Page {{ $p.PageNumber }}: {{ .Title }}|{{ .IsHome }}|{{ i18n \"hello\" }}|{{ .Permalink }}|{{  .Site.Data.hugo.slogan }}"),
+		0755); err != nil {
+		t.Fatalf("Failed to write layout file: %s", err)
+	}
+
+	if err := afero.WriteFile(mf,
+		filepath.Join("layouts", "index.fr.html"),
+		[]byte("{{ $p := .Paginator }}French Home Page {{ $p.PageNumber }}: {{ .Title }}|{{ .IsHome }}|{{ i18n \"hello\" }}|{{ .Permalink }}|{{  .Site.Data.hugo.slogan }}"),
 		0755); err != nil {
 		t.Fatalf("Failed to write layout file: %s", err)
 	}
@@ -1055,6 +1062,21 @@ func createMultiTestSitesForConfig(t *testing.T, siteConfig testSiteConfig, conf
 		t.Fatalf("Failed to write layout file: %s", err)
 	}
 
+	// A shortcode in multiple languages
+	if err := afero.WriteFile(mf,
+		filepath.Join("layouts", "shortcodes", "lingo.html"),
+		[]byte("LingoDefault"),
+		0755); err != nil {
+		t.Fatalf("Failed to write layout file: %s", err)
+	}
+
+	if err := afero.WriteFile(mf,
+		filepath.Join("layouts", "shortcodes", "lingo.fr.html"),
+		[]byte("LingoFrench"),
+		0755); err != nil {
+		t.Fatalf("Failed to write layout file: %s", err)
+	}
+
 	// Add some language files
 	if err := afero.WriteFile(mf,
 		filepath.Join("i18n", "en.yaml"),
@@ -1098,6 +1120,8 @@ publishdate: "2000-01-01"
 
 {{< shortcode >}}
 
+{{< lingo >}}
+
 NOTE: slug should be used as URL
 `)},
 		{Name: filepath.FromSlash("sect/doc1.fr.md"), Content: []byte(`---
@@ -1113,6 +1137,8 @@ publishdate: "2000-01-04"
 
 {{< shortcode >}}
 
+{{< lingo >}}
+
 NOTE: should be in the 'en' Page's 'Translations' field.
 NOTE: date is after "doc3"
 `)},
diff --git a/hugolib/page.go b/hugolib/page.go
index cf0a2144c..0f44b8b99 100644
--- a/hugolib/page.go
+++ b/hugolib/page.go
@@ -250,6 +250,7 @@ func (p *Page) createLayoutDescriptor() output.LayoutDescriptor {
 	return output.LayoutDescriptor{
 		Kind:    p.Kind,
 		Type:    p.Type(),
+		Lang:    p.Lang(),
 		Layout:  p.Layout,
 		Section: section,
 	}
diff --git a/hugolib/shortcode.go b/hugolib/shortcode.go
index 150d82c44..3cf472f82 100644
--- a/hugolib/shortcode.go
+++ b/hugolib/shortcode.go
@@ -157,6 +157,7 @@ func (sc shortcode) String() string {
 // Note that in the below, OutputFormat may be empty.
 // We will try to look for the most specific shortcode template available.
 type scKey struct {
+	Lang                 string
 	OutputFormat         string
 	Suffix               string
 	ShortcodePlaceholder string
@@ -166,8 +167,8 @@ func newScKey(m media.Type, shortcodeplaceholder string) scKey {
 	return scKey{Suffix: m.Suffix, ShortcodePlaceholder: shortcodeplaceholder}
 }
 
-func newScKeyFromOutputFormat(o output.Format, shortcodeplaceholder string) scKey {
-	return scKey{Suffix: o.MediaType.Suffix, OutputFormat: o.Name, ShortcodePlaceholder: shortcodeplaceholder}
+func newScKeyFromLangAndOutputFormat(lang string, o output.Format, shortcodeplaceholder string) scKey {
+	return scKey{Lang: lang, Suffix: o.MediaType.Suffix, OutputFormat: o.Name, ShortcodePlaceholder: shortcodeplaceholder}
 }
 
 func newDefaultScKey(shortcodeplaceholder string) scKey {
@@ -251,10 +252,11 @@ const innerCleanupExpand = "$1"
 func prepareShortcodeForPage(placeholder string, sc shortcode, parent *ShortcodeWithPage, p *Page) map[scKey]func() (string, error) {
 
 	m := make(map[scKey]func() (string, error))
+	lang := p.Lang()
 
 	for _, f := range p.outputFormats {
 		// The most specific template will win.
-		key := newScKeyFromOutputFormat(f, placeholder)
+		key := newScKeyFromLangAndOutputFormat(lang, f, placeholder)
 		m[key] = func() (string, error) {
 			return renderShortcode(key, sc, nil, p), nil
 		}
@@ -371,9 +373,11 @@ func (s *shortcodeHandler) updateDelta() bool {
 
 func (s *shortcodeHandler) contentShortcodesForOutputFormat(f output.Format) map[scKey]func() (string, error) {
 	contentShortcodesForOuputFormat := make(map[scKey]func() (string, error))
+	lang := s.p.Lang()
+
 	for shortcodePlaceholder := range s.shortcodes {
 
-		key := newScKeyFromOutputFormat(f, shortcodePlaceholder)
+		key := newScKeyFromLangAndOutputFormat(lang, f, shortcodePlaceholder)
 		renderFn, found := s.contentShortcodes[key]
 
 		if !found {
@@ -390,7 +394,7 @@ func (s *shortcodeHandler) contentShortcodesForOutputFormat(f output.Format) map
 		if !found {
 			panic(fmt.Sprintf("Shortcode %q could not be found", shortcodePlaceholder))
 		}
-		contentShortcodesForOuputFormat[newScKeyFromOutputFormat(f, shortcodePlaceholder)] = renderFn
+		contentShortcodesForOuputFormat[newScKeyFromLangAndOutputFormat(lang, f, shortcodePlaceholder)] = renderFn
 	}
 
 	return contentShortcodesForOuputFormat
@@ -676,12 +680,19 @@ func getShortcodeTemplateForTemplateKey(key scKey, shortcodeName string, t tpl.T
 
 	suffix := strings.ToLower(key.Suffix)
 	outFormat := strings.ToLower(key.OutputFormat)
+	lang := strings.ToLower(key.Lang)
 
 	if outFormat != "" && suffix != "" {
+		if lang != "" {
+			names = append(names, fmt.Sprintf("%s.%s.%s.%s", shortcodeName, lang, outFormat, suffix))
+		}
 		names = append(names, fmt.Sprintf("%s.%s.%s", shortcodeName, outFormat, suffix))
 	}
 
 	if suffix != "" {
+		if lang != "" {
+			names = append(names, fmt.Sprintf("%s.%s.%s", shortcodeName, lang, suffix))
+		}
 		names = append(names, fmt.Sprintf("%s.%s", shortcodeName, suffix))
 	}
 
diff --git a/hugolib/shortcode_test.go b/hugolib/shortcode_test.go
index 42da9e465..3d355f947 100644
--- a/hugolib/shortcode_test.go
+++ b/hugolib/shortcode_test.go
@@ -837,8 +837,8 @@ func TestReplaceShortcodeTokens(t *testing.T) {
 func TestScKey(t *testing.T) {
 	require.Equal(t, scKey{Suffix: "xml", ShortcodePlaceholder: "ABCD"},
 		newScKey(media.XMLType, "ABCD"))
-	require.Equal(t, scKey{Suffix: "html", OutputFormat: "AMP", ShortcodePlaceholder: "EFGH"},
-		newScKeyFromOutputFormat(output.AMPFormat, "EFGH"))
+	require.Equal(t, scKey{Lang: "en", Suffix: "html", OutputFormat: "AMP", ShortcodePlaceholder: "EFGH"},
+		newScKeyFromLangAndOutputFormat("en", output.AMPFormat, "EFGH"))
 	require.Equal(t, scKey{Suffix: "html", ShortcodePlaceholder: "IJKL"},
 		newDefaultScKey("IJKL"))
 
diff --git a/output/docshelper.go b/output/docshelper.go
index 1df45726c..c45e956e6 100644
--- a/output/docshelper.go
+++ b/output/docshelper.go
@@ -44,6 +44,7 @@ func createLayoutExamples() interface{} {
 		f              Format
 	}{
 		{`AMP home, with theme "demoTheme".`, LayoutDescriptor{Kind: "home"}, true, "", AMPFormat},
+		{`AMP home, French language".`, LayoutDescriptor{Kind: "home", Lang: "fr"}, false, "", AMPFormat},
 		{"JSON home, no theme.", LayoutDescriptor{Kind: "home"}, false, "", JSONFormat},
 		{fmt.Sprintf(`CSV regular, "layout: %s" in front matter.`, demoLayout), LayoutDescriptor{Kind: "page", Layout: demoLayout}, false, "", CSVFormat},
 		{fmt.Sprintf(`JSON regular, "type: %s" in front matter.`, demoType), LayoutDescriptor{Kind: "page", Type: demoType}, false, "", JSONFormat},
diff --git a/output/layout.go b/output/layout.go
index cacb92b80..6c054b6c4 100644
--- a/output/layout.go
+++ b/output/layout.go
@@ -26,6 +26,7 @@ type LayoutDescriptor struct {
 	Type    string
 	Section string
 	Kind    string
+	Lang    string
 	Layout  string
 }
 
@@ -55,31 +56,33 @@ func NewLayoutHandler(hasTheme bool) *LayoutHandler {
 
 const (
 
+	// TODO(bep) variations reduce to 1 "."
+
 	// The RSS templates doesn't map easily into the regular pages.
-	layoutsRSSHome         = `NAME.SUFFIX _default/NAME.SUFFIX _internal/_default/rss.xml`
-	layoutsRSSSection      = `section/SECTION.NAME.SUFFIX _default/NAME.SUFFIX NAME.SUFFIX _internal/_default/rss.xml`
-	layoutsRSSTaxonomy     = `taxonomy/SECTION.NAME.SUFFIX _default/NAME.SUFFIX NAME.SUFFIX _internal/_default/rss.xml`
-	layoutsRSSTaxonomyTerm = `taxonomy/SECTION.terms.NAME.SUFFIX _default/NAME.SUFFIX NAME.SUFFIX _internal/_default/rss.xml`
+	layoutsRSSHome         = `VARIATIONS _default/VARIATIONS _internal/_default/rss.xml`
+	layoutsRSSSection      = `section/SECTION.VARIATIONS _default/VARIATIONS VARIATIONS _internal/_default/rss.xml`
+	layoutsRSSTaxonomy     = `taxonomy/SECTION.VARIATIONS _default/VARIATIONS VARIATIONS _internal/_default/rss.xml`
+	layoutsRSSTaxonomyTerm = `taxonomy/SECTION.terms.VARIATIONS _default/VARIATIONS VARIATIONS _internal/_default/rss.xml`
 
-	layoutsHome    = "index.NAME.SUFFIX index.SUFFIX _default/list.NAME.SUFFIX _default/list.SUFFIX"
+	layoutsHome    = "index.VARIATIONS _default/list.VARIATIONS"
 	layoutsSection = `
-section/SECTION.NAME.SUFFIX section/SECTION.SUFFIX
-SECTION/list.NAME.SUFFIX SECTION/list.SUFFIX
-_default/section.NAME.SUFFIX _default/section.SUFFIX
-_default/list.NAME.SUFFIX _default/list.SUFFIX
-indexes/SECTION.NAME.SUFFIX indexes/SECTION.SUFFIX
-_default/indexes.NAME.SUFFIX _default/indexes.SUFFIX
+section/SECTION.VARIATIONS
+SECTION/list.VARIATIONS
+_default/section.VARIATIONS
+_default/list.VARIATIONS
+indexes/SECTION.VARIATIONS
+_default/indexes.VARIATIONS
 `
 	layoutsTaxonomy = `
-taxonomy/SECTION.NAME.SUFFIX taxonomy/SECTION.SUFFIX
-indexes/SECTION.NAME.SUFFIX indexes/SECTION.SUFFIX 
-_default/taxonomy.NAME.SUFFIX _default/taxonomy.SUFFIX
-_default/list.NAME.SUFFIX _default/list.SUFFIX
+taxonomy/SECTION.VARIATIONS
+indexes/SECTION.VARIATIONS 
+_default/taxonomy.VARIATIONS
+_default/list.VARIATIONS
 `
 	layoutsTaxonomyTerm = `
-taxonomy/SECTION.terms.NAME.SUFFIX taxonomy/SECTION.terms.SUFFIX
-_default/terms.NAME.SUFFIX _default/terms.SUFFIX
-indexes/indexes.NAME.SUFFIX indexes/indexes.SUFFIX
+taxonomy/SECTION.terms.VARIATIONS
+_default/terms.VARIATIONS
+indexes/indexes.VARIATIONS
 `
 )
 
@@ -185,14 +188,41 @@ func resolveListTemplate(d LayoutDescriptor, f Format,
 }
 
 func resolveTemplate(templ string, d LayoutDescriptor, f Format) []string {
-	delim := "."
-	if f.MediaType.Delimiter == "" {
-		delim = ""
+
+	// VARIATIONS will be replaced with
+	// .lang.name.suffix
+	// .name.suffix
+	// .lang.suffix
+	// .suffix
+	var replacementValues []string
+
+	name := strings.ToLower(f.Name)
+
+	if d.Lang != "" {
+		replacementValues = append(replacementValues, fmt.Sprintf("%s.%s.%s", d.Lang, name, f.MediaType.Suffix))
+	}
+
+	replacementValues = append(replacementValues, fmt.Sprintf("%s.%s", name, f.MediaType.Suffix))
+
+	if d.Lang != "" {
+		replacementValues = append(replacementValues, fmt.Sprintf("%s.%s", d.Lang, f.MediaType.Suffix))
+	}
+
+	isRSS := f.Name == RSSFormat.Name
+
+	if !isRSS {
+		replacementValues = append(replacementValues, f.MediaType.Suffix)
+	}
+
+	var layouts []string
+
+	templFields := strings.Fields(templ)
+
+	for _, field := range templFields {
+		for _, replacements := range replacementValues {
+			layouts = append(layouts, replaceKeyValues(field, "VARIATIONS", replacements, "SECTION", d.Section))
+		}
 	}
-	layouts := strings.Fields(replaceKeyValues(templ,
-		".SUFFIX", delim+f.MediaType.Suffix,
-		"NAME", strings.ToLower(f.Name),
-		"SECTION", d.Section))
 
 	return filterDotLess(layouts)
 }
@@ -201,9 +231,7 @@ func filterDotLess(layouts []string) []string {
 	var filteredLayouts []string
 
 	for _, l := range layouts {
-		// This may be constructed, but media types can be suffix-less, but can contain
-		// a delimiter.
-		l = strings.TrimSuffix(l, ".")
+		l = strings.Trim(l, ".")
 		// If media type has no suffix, we have "index" type of layouts in this list, which
 		// doesn't make much sense.
 		if strings.Contains(l, ".") {
diff --git a/output/layout_test.go b/output/layout_test.go
index 9d4d2f6d5..6fb958c9d 100644
--- a/output/layout_test.go
+++ b/output/layout_test.go
@@ -59,6 +59,8 @@ func TestLayout(t *testing.T) {
 	}{
 		{"Home", LayoutDescriptor{Kind: "home"}, true, "", ampType,
 			[]string{"index.amp.html", "index.html", "_default/list.amp.html", "_default/list.html", "theme/index.amp.html", "theme/index.html"}},
+		{"Home, french language", LayoutDescriptor{Kind: "home", Lang: "fr"}, true, "", ampType,
+			[]string{"index.fr.amp.html", "index.amp.html", "index.fr.html", "index.html", "_default/list.fr.amp.html", "_default/list.amp.html", "_default/list.fr.html", "_default/list.html", "theme/index.fr.amp.html", "theme/index.amp.html", "theme/index.fr.html"}},
 		{"Home, no ext or delim", LayoutDescriptor{Kind: "home"}, true, "", noExtDelimFormat,
 			[]string{"index.nem", "_default/list.nem"}},
 		{"Home, no ext", LayoutDescriptor{Kind: "home"}, true, "", noExt,