markup/goldmark: Support extras extension

Enables inclusion of these HTML elements in Markdown:

- Inserted Text (++inserted++)
- Mark Text (==marked==)
- Subscript (H~2~O)
- Superscript (1^st^)

markup/goldmark/convert.go

@@ -17,6 +17,7 @@ package goldmark
 import (
 	"bytes"
 
+	"github.com/gohugoio/hugo-goldmark-extensions/extras"
 	"github.com/gohugoio/hugo-goldmark-extensions/passthrough"
 	"github.com/gohugoio/hugo/markup/goldmark/hugocontext"
 	"github.com/yuin/goldmark/util"
@@ -113,6 +114,15 @@ func newMarkdown(pcfg converter.ProviderConfig) goldmark.Markdown {
 
 	extensions = append(extensions, images.New(cfg.Parser.WrapStandAloneImageWithinParagraph))
 
+	extensions = append(extensions, extras.New(
+		extras.Config{
+			Insert:      extras.InsertConfig{Enable: cfg.Extensions.Extras.Insert.Enable},
+			Mark:        extras.MarkConfig{Enable: cfg.Extensions.Extras.Mark.Enable},
+			Subscript:   extras.SubscriptConfig{Enable: cfg.Extensions.Extras.Subscript.Enable},
+			Superscript: extras.SuperscriptConfig{Enable: cfg.Extensions.Extras.Superscript.Enable},
+		},
+	))
+
 	if mcfg.Highlight.CodeFences {
 		extensions = append(extensions, codeblocks.New())
 	}

markup/goldmark/goldmark_config/config.go

@@ -49,6 +49,20 @@ var Default = Config{
 			EastAsianLineBreaksStyle: "simple",
 			EscapedSpace:             false,
 		},
+		Extras: Extras{
+			Superscript: Superscript{
+				Enable: false,
+			},
+			Subscript: Subscript{
+				Enable: false,
+			},
+			Insert: Insert{
+				Enable: false,
+			},
+			Mark: Mark{
+				Enable: false,
+			},
+		},
 		Passthrough: Passthrough{
 			Enable: false,
 			Delimiters: DelimitersConfig{
@@ -112,6 +126,7 @@ type Extensions struct {
 	Typographer    Typographer
 	Footnote       bool
 	DefinitionList bool
+	Extras         Extras
 	Passthrough    Passthrough
 
 	// GitHub flavored markdown
@@ -150,7 +165,32 @@ type Typographer struct {
 	Apostrophe string
 }
 
-// Passthrough hold passthrough configuration.
+// Extras holds extras configuration.
+// github.com/hugoio/hugo-goldmark-extensions/extras
+type Extras struct {
+	Insert      Insert
+	Mark        Mark
+	Subscript   Subscript
+	Superscript Superscript
+}
+
+type Insert struct {
+	Enable bool
+}
+
+type Mark struct {
+	Enable bool
+}
+
+type Subscript struct {
+	Enable bool
+}
+
+type Superscript struct {
+	Enable bool
+}
+
+// Passthrough holds passthrough configuration.
 // github.com/hugoio/hugo-goldmark-extensions/passthrough
 type Passthrough struct {
 	// Whether to enable the extension

markup/goldmark/goldmark_integration_test.go

@@ -744,3 +744,53 @@ a^*=x-b^*
 %!%
 	`)
 }
+
+func TestExtrasExtension(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+[markup.goldmark.extensions.extras.insert]
+enable = false
+[markup.goldmark.extensions.extras.mark]
+enable = false
+[markup.goldmark.extensions.extras.subscript]
+enable = false
+[markup.goldmark.extensions.extras.superscript]
+enable = false
+-- layouts/index.html --
+{{ .Content }}
+-- content/_index.md --
+---
+title: home
+---
+++insert++
+
+==mark==
+
+H~2~0
+
+1^st^
+`
+
+	b := hugolib.Test(t, files)
+
+	b.AssertFileContent("public/index.html",
+		"<p>++insert++</p>",
+		"<p>==mark==</p>",
+		"<p>H~2~0</p>",
+		"<p>1^st^</p>",
+	)
+
+	files = strings.ReplaceAll(files, "enable = false", "enable = true")
+
+	b = hugolib.Test(t, files)
+
+	b.AssertFileContent("public/index.html",
+		"<p><ins>insert</ins></p>",
+		"<p><mark>mark</mark></p>",
+		"<p>H<sub>2</sub>0</p>",
+		"<p>1<sup>st</sup></p>",
+	)
+}