Make Page an interface

The main motivation of this commit is to add a `page.Page` interface to replace the very file-oriented `hugolib.Page` struct.
This is all a preparation step for issue  #5074, "pages from other data sources".

But this also fixes a set of annoying limitations, especially related to custom output formats, and shortcodes.

Most notable changes:

* The inner content of shortcodes using the `{{%` as the outer-most delimiter will now be sent to the content renderer, e.g. Blackfriday.
  This means that any markdown will partake in the global ToC and footnote context etc.
* The Custom Output formats are now "fully virtualized". This removes many of the current limitations.
* The taxonomy list type now has a reference to the `Page` object.
  This improves the taxonomy template `.Title` situation and make common template constructs much simpler.

See #5074
Fixes #5763
Fixes #5758
Fixes #5090
Fixes #5204
Fixes #4695
Fixes #5607
Fixes #5707
Fixes #5719
Fixes #3113
Fixes #5706
Fixes #5767
Fixes #5723
Fixes #5769
Fixes #5770
Fixes #5771
Fixes #5759
Fixes #5776
Fixes #5777
Fixes #5778

20 files changed, 739 insertions, 205 deletions

diff --git a/tpl/collections/apply_test.go b/tpl/collections/apply_test.go
index 0878844b2..edec3da18 100644
--- a/tpl/collections/apply_test.go
+++ b/tpl/collections/apply_test.go
@@ -1,4 +1,4 @@
-// Copyright 2017 The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -29,6 +29,10 @@ func (templateFinder) Lookup(name string) (tpl.Template, bool) {
 	return nil, false
 }
 
+func (templateFinder) LookupVariant(name string, variants tpl.TemplateVariants) (tpl.Template, bool, bool) {
+	return nil, false, false
+}
+
 func (templateFinder) GetFuncs() map[string]interface{} {
 	return map[string]interface{}{
 		"print": fmt.Sprint,
diff --git a/tpl/collections/collections.go b/tpl/collections/collections.go
index bad65369f..92a61e575 100644
--- a/tpl/collections/collections.go
+++ b/tpl/collections/collections.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -329,13 +329,17 @@ func (ns *Namespace) Group(key interface{}, items interface{}) (interface{}, err
 		return nil, errors.New("nil is not a valid key to group by")
 	}
 
+	if g, ok := items.(collections.Grouper); ok {
+		return g.Group(key, items)
+	}
+
 	in := newSliceElement(items)
 
 	if g, ok := in.(collections.Grouper); ok {
 		return g.Group(key, items)
 	}
 
-	return nil, fmt.Errorf("grouping not supported for type %T", items)
+	return nil, fmt.Errorf("grouping not supported for type %T %T", items, in)
 }
 
 // IsSet returns whether a given array, channel, slice, or map has a key
diff --git a/tpl/collections/collections_test.go b/tpl/collections/collections_test.go
index 0edb8299f..103aee59e 100644
--- a/tpl/collections/collections_test.go
+++ b/tpl/collections/collections_test.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -311,16 +311,16 @@ func TestIn(t *testing.T) {
 	}
 }
 
-type page struct {
+type testPage struct {
 	Title string
 }
 
-func (p page) String() string {
+func (p testPage) String() string {
 	return "p-" + p.Title
 }
 
-type pagesPtr []*page
-type pagesVals []page
+type pagesPtr []*testPage
+type pagesVals []testPage
 
 func TestIntersect(t *testing.T) {
 	t.Parallel()
@@ -328,15 +328,15 @@ func TestIntersect(t *testing.T) {
 	ns := New(&deps.Deps{})
 
 	var (
-		p1 = &page{"A"}
-		p2 = &page{"B"}
-		p3 = &page{"C"}
-		p4 = &page{"D"}
-
-		p1v = page{"A"}
-		p2v = page{"B"}
-		p3v = page{"C"}
-		p4v = page{"D"}
+		p1 = &testPage{"A"}
+		p2 = &testPage{"B"}
+		p3 = &testPage{"C"}
+		p4 = &testPage{"D"}
+
+		p1v = testPage{"A"}
+		p2v = testPage{"B"}
+		p3v = testPage{"C"}
+		p4v = testPage{"D"}
 	)
 
 	for i, test := range []struct {
@@ -672,14 +672,14 @@ func TestUnion(t *testing.T) {
 	ns := New(&deps.Deps{})
 
 	var (
-		p1 = &page{"A"}
-		p2 = &page{"B"}
+		p1 = &testPage{"A"}
+		p2 = &testPage{"B"}
 		//		p3 = &page{"C"}
-		p4 = &page{"D"}
+		p4 = &testPage{"D"}
 
-		p1v = page{"A"}
+		p1v = testPage{"A"}
 		//p2v = page{"B"}
-		p3v = page{"C"}
+		p3v = testPage{"C"}
 		//p4v = page{"D"}
 	)
 
diff --git a/tpl/template.go b/tpl/template.go
index 3225814c0..07152166a 100644
--- a/tpl/template.go
+++ b/tpl/template.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -21,6 +21,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/gohugoio/hugo/output"
+
 	"github.com/gohugoio/hugo/common/herrors"
 
 	"github.com/gohugoio/hugo/hugofs"
@@ -37,7 +39,8 @@ import (
 )
 
 var (
-	_ TemplateExecutor = (*TemplateAdapter)(nil)
+	_ TemplateExecutor     = (*TemplateAdapter)(nil)
+	_ TemplateInfoProvider = (*TemplateAdapter)(nil)
 )
 
 // TemplateHandler manages the collection of templates.
@@ -53,17 +56,47 @@ type TemplateHandler interface {
 	RebuildClone()
 }
 
+// TemplateVariants describes the possible variants of a template.
+// All of these may be empty.
+type TemplateVariants struct {
+	Language     string
+	OutputFormat output.Format
+}
+
 // TemplateFinder finds templates.
 type TemplateFinder interface {
+	TemplateLookup
+	TemplateLookupVariant
+}
+
+type TemplateLookup interface {
 	Lookup(name string) (Template, bool)
 }
 
+type TemplateLookupVariant interface {
+	// TODO(bep) this currently only works for shortcodes.
+	// We may unify and expand this variant pattern to the
+	// other templates, but we need this now for the shortcodes to
+	// quickly determine if a shortcode has a template for a given
+	// output format.
+	// It returns the template, if it was found or not and if there are
+	// alternative representations (output format, language).
+	// We are currently only interested in output formats, so we should improve
+	// this for speed.
+	LookupVariant(name string, variants TemplateVariants) (Template, bool, bool)
+}
+
 // Template is the common interface between text/template and html/template.
 type Template interface {
 	Execute(wr io.Writer, data interface{}) error
 	Name() string
 }
 
+// TemplateInfoProvider provides some contextual information about a template.
+type TemplateInfoProvider interface {
+	TemplateInfo() Info
+}
+
 // TemplateParser is used to parse ad-hoc templates, e.g. in the Resource chain.
 type TemplateParser interface {
 	Parse(name, tpl string) (Template, error)
@@ -92,6 +125,8 @@ type TemplateAdapter struct {
 	Template
 	Metrics metrics.Provider
 
+	Info Info
+
 	// The filesystem where the templates are stored.
 	Fs afero.Fs
 
@@ -133,6 +168,10 @@ func (t *TemplateAdapter) Execute(w io.Writer, data interface{}) (execErr error)
 	return
 }
 
+func (t *TemplateAdapter) TemplateInfo() Info {
+	return t.Info
+}
+
 // The identifiers may be truncated in the log, e.g.
 // "executing "main" at <$scaled.SRelPermalin...>: can't evaluate field SRelPermalink in type *resource.Image"
 var identifiersRe = regexp.MustCompile("at \\<(.*?)(\\.{3})?\\>:")
diff --git a/tpl/template_info.go b/tpl/template_info.go
new file mode 100644
index 000000000..8568f46f0
--- /dev/null
+++ b/tpl/template_info.go
@@ -0,0 +1,35 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tpl
+
+// Increments on breaking changes.
+const TemplateVersion = 2
+
+// Info holds some info extracted from a parsed template.
+type Info struct {
+
+	// Set for shortcode templates with any {{ .Inner }}
+	IsInner bool
+
+	// Config extracted from template.
+	Config Config
+}
+
+type Config struct {
+	Version int
+}
+
+var DefaultConfig = Config{
+	Version: TemplateVersion,
+}
diff --git a/tpl/tplimpl/ace.go b/tpl/tplimpl/ace.go
index 6fb4ca439..7a1f849f4 100644
--- a/tpl/tplimpl/ace.go
+++ b/tpl/tplimpl/ace.go
@@ -1,4 +1,4 @@
-// Copyright 2017-present The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -14,7 +14,6 @@
 package tplimpl
 
 import (
-	"html/template"
 	"path/filepath"
 
 	"strings"
@@ -52,15 +51,15 @@ func (t *templateHandler) addAceTemplate(name, basePath, innerPath string, baseC
 		return err
 	}
 
-	if err := applyTemplateTransformersToHMLTTemplate(templ); err != nil {
+	isShort := isShortcode(name)
+
+	info, err := applyTemplateTransformersToHMLTTemplate(isShort, templ)
+	if err != nil {
 		return err
 	}
 
-	if strings.Contains(name, "shortcodes") {
-		// We need to keep track of one ot the output format's shortcode template
-		// without knowing the rendering context.
-		clone := template.Must(templ.Clone())
-		t.html.t.AddParseTree(withoutExt, clone.Tree)
+	if isShort {
+		t.addShortcodeVariant(name, info, templ)
 	}
 
 	return nil
diff --git a/tpl/tplimpl/embedded/generate/generate.go b/tpl/tplimpl/embedded/generate/generate.go
index 76a167a99..a48e00756 100644
--- a/tpl/tplimpl/embedded/generate/generate.go
+++ b/tpl/tplimpl/embedded/generate/generate.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -63,7 +63,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	fmt.Fprint(file, `// Copyright 2018 The Hugo Authors. All rights reserved.
+	fmt.Fprint(file, `// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/tpl/tplimpl/embedded/templates.autogen.go b/tpl/tplimpl/embedded/templates.autogen.go
index ed9ba35ac..d55e5b307 100644
--- a/tpl/tplimpl/embedded/templates.autogen.go
+++ b/tpl/tplimpl/embedded/templates.autogen.go
@@ -1,4 +1,4 @@
-// Copyright 2018 The Hugo Authors. All rights reserved.
+// Copyright 2019 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -19,7 +19,13 @@ package embedded
 // EmbeddedTemplates represents all embedded templates.
 var EmbeddedTemplates = [][2]string{
 	{`_default/robots.txt`, `User-agent: *`},
-	{`_default/rss.xml`, `<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
+	{`_default/rss.xml`, `{{- $pages := .Data.Pages -}}
+{{- $limit := .Site.Config.Services.RSS.Limit -}}
+{{- if ge $limit 1 -}}
+{{- $pages = $pages | first $limit -}}
+{{- end -}}
+{{- printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>" | safeHTML }}
+<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
   <channel>
     <title>{{ if eq  .Title  .Site.Title }}{{ .Site.Title }}{{ else }}{{ with .Title }}{{.}} on {{ end }}{{ .Site.Title }}{{ end }}</title>
     <link>{{ .Permalink }}</link>
@@ -33,7 +39,7 @@ var EmbeddedTemplates = [][2]string{
     {{ with .OutputFormats.Get "RSS" }}
 	{{ printf "<atom:link href=%q rel=\"self\" type=%q />" .Permalink .MediaType | safeHTML }}
     {{ end }}
-    {{ range .Data.Pages }}
+    {{ range $pages }}
     <item>
       <title>{{ .Title }}</title>
       <link>{{ .Permalink }}</link>
@@ -45,7 +51,8 @@ var EmbeddedTemplates = [][2]string{
     {{ end }}
   </channel>
 </rss>`},
-	{`_default/sitemap.xml`, `<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
+	{`_default/sitemap.xml`, `{{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>" | safeHTML }}
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
   xmlns:xhtml="http://www.w3.org/1999/xhtml">
   {{ range .Data.Pages }}
   <url>
@@ -55,18 +62,19 @@ var EmbeddedTemplates = [][2]string{
     <priority>{{ .Sitemap.Priority }}</priority>{{ end }}{{ if .IsTranslated }}{{ range .Translations }}
     <xhtml:link
                 rel="alternate"
-                hreflang="{{ .Lang }}"
+                hreflang="{{ .Language.Lang }}"
                 href="{{ .Permalink }}"
                 />{{ end }}
     <xhtml:link
                 rel="alternate"
-                hreflang="{{ .Lang }}"
+                hreflang="{{ .Language.Lang }}"
                 href="{{ .Permalink }}"
                 />{{ end }}
   </url>
   {{ end }}
 </urlset>`},
-	{`_default/sitemapindex.xml`, `<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+	{`_default/sitemapindex.xml`, `{{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>" | safeHTML }}
+<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
 	{{ range . }}
 	<sitemap>
 	   	<loc>{{ .SitemapAbsURL }}</loc>
@@ -77,7 +85,7 @@ var EmbeddedTemplates = [][2]string{
 	{{ end }}
 </sitemapindex>
 `},
-	{`disqus.html`, `{{- $pc := .Page.Site.Config.Privacy.Disqus -}}
+	{`disqus.html`, `{{- $pc := .Site.Config.Privacy.Disqus -}}
 {{- if not $pc.Disable -}}
 {{ if .Site.DisqusShortname }}<div id="disqus_thread"></div>
 <script type="application/javascript">
diff --git a/tpl/tplimpl/embedded/templates/_default/rss.xml b/tpl/tplimpl/embedded/templates/_default/rss.xml
index abba0b28a..675ecd43c 100644
--- a/tpl/tplimpl/embedded/templates/_default/rss.xml
+++ b/tpl/tplimpl/embedded/templates/_default/rss.xml
@@ -1,3 +1,9 @@
+{{- $pages := .Data.Pages -}}
+{{- $limit := .Site.Config.Services.RSS.Limit -}}
+{{- if ge $limit 1 -}}
+{{- $pages = $pages | first $limit -}}
+{{- end -}}
+{{- printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>" | safeHTML }}
 <rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
   <channel>
     <title>{{ if eq  .Title  .Site.Title }}{{ .Site.Title }}{{ else }}{{ with .Title }}{{.}} on {{ end }}{{ .Site.Title }}{{ end }}</title>
@@ -12,7 +18,7 @@
     {{ with .OutputFormats.Get "RSS" }}
 	{{ printf "<atom:link href=%q rel=\"self\" type=%q />" .Permalink .MediaType | safeHTML }}
     {{ end }}
-    {{ range .Data.Pages }}
+    {{ range $pages }}
     <item>
       <title>{{ .Title }}</title>
       <link>{{ .Permalink }}</link>
diff --git a/tpl/tplimpl/embedded/templates/_default/sitemap.xml b/tpl/tplimpl/embedded/templates/_default/sitemap.xml
index e0a2b189d..f5b44c410 100644
--- a/tpl/tplimpl/embedded/templates/_default/sitemap.xml
+++ b/tpl/tplimpl/embedded/templates/_default/sitemap.xml
@@ -1,3 +1,4 @@
+{{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>" | safeHTML }}
 <urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
   xmlns:xhtml="http://www.w3.org/1999/xhtml">
   {{ range .Data.Pages }}
@@ -8,12 +9,12 @@
     <priority>{{ .Sitemap.Priority }}</priority>{{ end }}{{ if .IsTranslated }}{{ range .Translations }}
     <xhtml:link
                 rel="alternate"
-                hreflang="{{ .Lang }}"
+                hreflang="{{ .Language.Lang }}"
                 href="{{ .Permalink }}"
                 />{{ end }}
     <xhtml:link
                 rel="alternate"
-                hreflang="{{ .Lang }}"
+                hreflang="{{ .Language.Lang }}"
                 href="{{ .Permalink }}"
                 />{{ end }}
   </url>
diff --git a/tpl/tplimpl/embedded/templates/_default/sitemapindex.xml b/tpl/tplimpl/embedded/templates/_default/sitemapindex.xml
index 4cd289fe9..60724c7b8 100644
--- a/tpl/tplimpl/embedded/templates/_default/sitemapindex.xml
+++ b/tpl/tplimpl/embedded/templates/_default/sitemapindex.xml
@@ -1,3 +1,4 @@
+{{ printf "<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\" ?>" | safeHTML }}
 <sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
 	{{ range . }}
 	<sitemap>
diff --git a/tpl/tplimpl/embedded/templates/disqus.html b/tpl/tplimpl/embedded/templates/disqus.html
index 178d84caf..ab51bb5c0 100644
--- a/tpl/tplimpl/embedded/templates/disqus.html
+++ b/tpl/tplimpl/embedded/templates/disqus.html
@@ -1,4 +1,4 @@
-{{- $pc := .Page.Site.Config.Privacy.Disqus -}}
+{{- $pc := .Site.Config.Privacy.Disqus -}}
 {{- if not $pc.Disable -}}
 {{ if .Site.DisqusShortname }}<div id="disqus_thread"></div>
 <script type="application/javascript">
diff --git a/tpl/tplimpl/shortcodes.go b/tpl/tplimpl/shortcodes.go
new file mode 100644
index 000000000..8577fbeed
--- /dev/null
+++ b/tpl/tplimpl/shortcodes.go
@@ -0,0 +1,148 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tplimpl
+
+import (
+	"strings"
+
+	"github.com/gohugoio/hugo/tpl"
+)
+
+// Currently lang, outFormat, suffix
+const numTemplateVariants = 3
+
+type shortcodeVariant struct {
+
+	// The possible variants: lang, outFormat, suffix
+	// gtag
+	// gtag.html
+	// gtag.no.html
+	// gtag.no.amp.html
+	// A slice of length numTemplateVariants.
+	variants []string
+
+	info  tpl.Info
+	templ tpl.Template
+}
+
+type shortcodeTemplates struct {
+	variants []shortcodeVariant
+}
+
+func (s *shortcodeTemplates) indexOf(variants []string) int {
+L:
+	for i, v1 := range s.variants {
+		for i, v2 := range v1.variants {
+			if v2 != variants[i] {
+				continue L
+			}
+		}
+		return i
+	}
+	return -1
+}
+
+func (s *shortcodeTemplates) fromVariants(variants tpl.TemplateVariants) (shortcodeVariant, bool) {
+	return s.fromVariantsSlice([]string{
+		variants.Language,
+		strings.ToLower(variants.OutputFormat.Name),
+		variants.OutputFormat.MediaType.Suffix(),
+	})
+}
+
+// Get the most specific template given a full name, e.g  gtag.no.amp.html.
+func (s *shortcodeTemplates) fromName(name string) (shortcodeVariant, bool) {
+	return s.fromVariantsSlice(templateVariants(name))
+}
+
+func (s *shortcodeTemplates) fromVariantsSlice(variants []string) (shortcodeVariant, bool) {
+	var (
+		bestMatch       shortcodeVariant
+		bestMatchWeight int
+	)
+
+	for _, variant := range s.variants {
+		w := s.compareVariants(variants, variant.variants)
+		if bestMatchWeight == 0 || w > bestMatchWeight {
+			bestMatch = variant
+			bestMatchWeight = w
+		}
+	}
+
+	return bestMatch, true
+}
+
+// calculate a weight for two string slices of same lenght.
+// higher value means "better match".
+func (s *shortcodeTemplates) compareVariants(a, b []string) int {
+
+	weight := 0
+	for i, av := range a {
+		bv := b[i]
+		if av == bv {
+			weight++
+		} else {
+			weight--
+		}
+	}
+	return weight
+}
+
+func templateVariants(name string) []string {
+	_, variants := templateNameAndVariants(name)
+	return variants
+}
+
+func templateNameAndVariants(name string) (string, []string) {
+
+	variants := make([]string, numTemplateVariants)
+
+	parts := strings.Split(name, ".")
+
+	if len(parts) <= 1 {
+		// No variants.
+		return name, variants
+	}
+
+	name = parts[0]
+	parts = parts[1:]
+	lp := len(parts)
+	start := len(variants) - lp
+
+	for i, j := start, 0; i < len(variants); i, j = i+1, j+1 {
+		variants[i] = parts[j]
+	}
+
+	if lp > 1 && lp < len(variants) {
+		for i := lp - 1; i > 0; i-- {
+			variants[i-1] = variants[i]
+		}
+	}
+
+	if lp == 1 {
+		// Suffix only. Duplicate it into the output format field to
+		// make HTML win over AMP.
+		variants[len(variants)-2] = variants[len(variants)-1]
+	}
+
+	return name, variants
+}
+
+func isShortcode(name string) bool {
+	return strings.Contains(name, "shortcodes/")
+}
+
+func isInternal(name string) bool {
+	return strings.HasPrefix(name, "_internal/")
+}
diff --git a/tpl/tplimpl/shortcodes_test.go b/tpl/tplimpl/shortcodes_test.go
new file mode 100644
index 000000000..6909feda7
--- /dev/null
+++ b/tpl/tplimpl/shortcodes_test.go
@@ -0,0 +1,94 @@
+// Copyright 2019 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tplimpl
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestShortcodesTemplate(t *testing.T) {
+
+	t.Run("isShortcode", func(t *testing.T) {
+		assert := require.New(t)
+		assert.True(isShortcode("shortcodes/figures.html"))
+		assert.True(isShortcode("_internal/shortcodes/figures.html"))
+		assert.False(isShortcode("shortcodes\\figures.html"))
+		assert.False(isShortcode("myshortcodes"))
+
+	})
+
+	t.Run("variantsFromName", func(t *testing.T) {
+		assert := require.New(t)
+		assert.Equal([]string{"", "html", "html"}, templateVariants("figure.html"))
+		assert.Equal([]string{"no", "no", "html"}, templateVariants("figure.no.html"))
+		assert.Equal([]string{"no", "amp", "html"}, templateVariants("figure.no.amp.html"))
+		assert.Equal([]string{"amp", "amp", "html"}, templateVariants("figure.amp.html"))
+
+		name, variants := templateNameAndVariants("figure.html")
+		assert.Equal("figure", name)
+		assert.Equal([]string{"", "html", "html"}, variants)
+
+	})
+
+	t.Run("compareVariants", func(t *testing.T) {
+		assert := require.New(t)
+		var s *shortcodeTemplates
+
+		tests := []struct {
+			name     string
+			name1    string
+			name2    string
+			expected int
+		}{
+			{"Same suffix", "figure.html", "figure.html", 3},