markup/goldmark: Enhance footnote extension with backlinkHTML option

This commit introduces a new option, backlinkHTML, to the Goldmark
footnote extension. This allows users to the set custom text for
footnote backlink anchors.

Closes #11434

docs/data/docs.yaml

@@ -1239,6 +1239,7 @@ config:
           superscript:
             enable: false
         footnote:
+          backlinkHTML: '↩︎'
           enable: true
           enableAutoIDPrefix: false
         linkify: true

markup/goldmark/convert.go

@@ -177,14 +177,17 @@ func newMarkdown(pcfg converter.ProviderConfig) goldmark.Markdown {
 	}
 
 	if cfg.Extensions.Footnote.Enable {
+		opts := []extension.FootnoteOption{}
+		opts = append(opts, extension.WithFootnoteBacklinkHTML(cfg.Extensions.Footnote.BacklinkHTML))
 		if cfg.Extensions.Footnote.EnableAutoIDPrefix {
-			extensions = append(extensions, extension.NewFootnote(extension.WithFootnoteIDPrefixFunction(func(n ast.Node) []byte {
-				documentID := n.OwnerDocument().Meta()["documentID"].(string)
-				return []byte("h" + documentID)
-			})))
-		} else {
-			extensions = append(extensions, extension.Footnote)
+			opts = append(opts,
+				extension.WithFootnoteIDPrefixFunction(func(n ast.Node) []byte {
+					documentID := n.OwnerDocument().Meta()["documentID"].(string)
+					return []byte("h" + documentID)
+				}))
 		}
+		f := extension.NewFootnote(opts...)
+		extensions = append(extensions, f)
 	}
 
 	if cfg.Extensions.CJK.Enable {

markup/goldmark/goldmark_config/config.go

@@ -43,6 +43,7 @@ var Default = Config{
 		Footnote: Footnote{
 			Enable:             true,
 			EnableAutoIDPrefix: false,
+			BacklinkHTML:       "↩︎",
 		},
 		DefinitionList:  true,
 		Table:           true,
@@ -173,6 +174,7 @@ type Extensions struct {
 type Footnote struct {
 	Enable             bool
 	EnableAutoIDPrefix bool
+	BacklinkHTML       string
 }
 
 // Typographer holds typographer configuration.

markup/goldmark/goldmark_integration_test.go

@@ -971,6 +971,7 @@ disableKinds = ['home','rss','section','sitemap','taxonomy','term']
 [markup.goldmark.extensions.footnote]
 enable = false
 enableAutoIDPrefix = false
+TBD = 'back'
 -- layouts/all.html --
 {{ .Content }}
 -- content/p1.md --
@@ -1000,6 +1001,8 @@ foo[^1] and bar[^2]
 {{ end }}
 `
 
+	// test enableAutoIDPrefix
+
 	want := "<p>foo[^1] and bar[^2]</p>\n<p>[^1]: footnote one\n[^2]: footnote two</p>"
 	b := hugolib.Test(t, files)
 	b.AssertFileContent("public/p1/index.html", want)
@@ -1029,4 +1032,12 @@ foo[^1] and bar[^2]
 	b.AssertFileContent("public/p4/index.html",
 		"<p>foo<sup id=\"ha35b794ad6e8626cfnref:1\"><a href=\"#ha35b794ad6e8626cfn:1\" class=\"footnote-ref\" role=\"doc-noteref\">1</a></sup> and bar<sup id=\"ha35b794ad6e8626cfnref:2\"><a href=\"#ha35b794ad6e8626cfn:2\" class=\"footnote-ref\" role=\"doc-noteref\">2</a></sup></p>\n<div class=\"footnotes\" role=\"doc-endnotes\">\n<hr>\n<ol>\n<li id=\"ha35b794ad6e8626cfn:1\">\n<p>footnote one&#160;<a href=\"#ha35b794ad6e8626cfnref:1\" class=\"footnote-backref\" role=\"doc-backlink\">&#x21a9;&#xfe0e;</a></p>\n</li>\n<li id=\"ha35b794ad6e8626cfn:2\">\n<p>footnote two&#160;<a href=\"#ha35b794ad6e8626cfnref:2\" class=\"footnote-backref\" role=\"doc-backlink\">&#x21a9;&#xfe0e;</a></p>\n</li>\n</ol>\n</div>",
 	)
+
+	// test backlinkHTML
+
+	files = strings.ReplaceAll(files, "TBD", "backlinkHTML")
+	b = hugolib.Test(t, files)
+	b.AssertFileContent("public/p1/index.html",
+		"<p>foo<sup id=\"hb5cdcabc9e678612fnref:1\"><a href=\"#hb5cdcabc9e678612fn:1\" class=\"footnote-ref\" role=\"doc-noteref\">1</a></sup> and bar<sup id=\"hb5cdcabc9e678612fnref:2\"><a href=\"#hb5cdcabc9e678612fn:2\" class=\"footnote-ref\" role=\"doc-noteref\">2</a></sup></p>\n<div class=\"footnotes\" role=\"doc-endnotes\">\n<hr>\n<ol>\n<li id=\"hb5cdcabc9e678612fn:1\">\n<p>footnote one&#160;<a href=\"#hb5cdcabc9e678612fnref:1\" class=\"footnote-backref\" role=\"doc-backlink\">back</a></p>\n</li>\n<li id=\"hb5cdcabc9e678612fn:2\">\n<p>footnote two&#160;<a href=\"#hb5cdcabc9e678612fnref:2\" class=\"footnote-backref\" role=\"doc-backlink\">back</a></p>\n</li>\n</ol>\n</div>",
+	)
 }