extras: Implement delete extension

With Goldmark v1.7.1 and earlier, the Goldmark "strikethrough" extension was triggered by wrapping text within a pair of double-tilde characters. With Goldmark v1.7.2 and later, to provide full GFM compatibility, the Goldmark "strikethrough" extension is triggered by wrapping text within a pair of single- or double-tilde characters. This change created a conflict with the Hugo Goldmark Extras "subscript" extension. When enabling the Hugo Goldmark Extras "subscript" extension, if you want to render subscript and strikethrough text concurrently, you must: 1. Disable the Goldmark "strikethrough" extension 2. Enable the Hugo Goldmark Extras "delete" extension
gohugoio · Jun 17, 2024 · 4d4fcd0 · 4d4fcd0
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diff --git a/extras/_test/delete.txt b/extras/_test/delete.txt
@@ -0,0 +1,18 @@
+1
+//- - - - - - - - -//
+~~Hi~~ Hello, world!
+//- - - - - - - - -//
+<p><del>Hi</del> Hello, world!</p>
+//= = = = = = = = = = = = = = = = = = = = = = = =//
+
+
+
+2
+//- - - - - - - - -//
+This ~~has a
+
+new paragraph~~.
+//- - - - - - - - -//
+<p>This ~~has a</p>
+<p>new paragraph~~.</p>
+//= = = = = = = = = = = = = = = = = = = = = = = =//
diff --git a/extras/_test/insert.txt b/extras/_test/insert.txt
@@ -1,43 +1,22 @@
 1
 //- - - - - - - - -//
-++Hi++ Hello, world!
+Hello ++,++ world!
 //- - - - - - - - -//
-<p><ins>Hi</ins> Hello, world!</p>
+<p>Hello <ins>,</ins> world!</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
 2
 //- - - - - - - - -//
-This ++has a
+This ++expression is stretched over a
 
-new paragraph++.
+paragraph++.
 //- - - - - - - - -//
-<p>This ++has a</p>
-<p>new paragraph++.</p>
+<p>This ++expression is stretched over a</p>
+<p>paragraph++.</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
 3
 //- - - - - - - - -//
-x ++++foo++ bar++
-//- - - - - - - - -//
-<p>x <ins><ins>foo</ins> bar</ins></p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-4
-//- - - - - - - - -//
-x ++foo ++bar++++
-//- - - - - - - - -//
-<p>x <ins>foo <ins>bar</ins></ins></p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-5
-//- - - - - - - - -//
-x ++++foo++++
-//- - - - - - - - -//
-<p>x <ins><ins>foo</ins></ins></p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-6
-//- - - - - - - - -//
 **++test**++
 
 ++**test++**
@@ -46,7 +25,7 @@ x ++++foo++++
 <p><ins>**test</ins>**</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-7
+4
 //- - - - - - - - -//
 [++link]()++
 

diff --git a/extras/_test/mark.txt b/extras/_test/mark.txt
@@ -17,27 +17,6 @@ new paragraph==.
 
 3
 //- - - - - - - - -//
-x ====foo== bar==
-//- - - - - - - - -//
-<p>x <mark><mark>foo</mark> bar</mark></p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-4
-//- - - - - - - - -//
-x ==foo ==bar====
-//- - - - - - - - -//
-<p>x <mark>foo <mark>bar</mark></mark></p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-5
-//- - - - - - - - -//
-x ====foo====
-//- - - - - - - - -//
-<p>x <mark><mark>foo</mark></mark></p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-6
-//- - - - - - - - -//
 **==test**==
 
 ==**test==**
@@ -46,7 +25,7 @@ x ====foo====
 <p><mark>**test</mark>**</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-7
+4
 //- - - - - - - - -//
 [==link]()==
 

diff --git a/extras/_test/subscript.txt b/extras/_test/subscript.txt
@@ -40,23 +40,30 @@ x~i~ + x~j~
 <p><sub>foo bar</sub></p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-7: Mixed subscript and strikethrough
-//- - - - - - - - -//
-~~x~foobar~~~
-//- - - - - - - - -//
-<p><del>x<sub>foobar</sub></del></p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-8: Tildes in the middle and text before
+7: Tildes in the middle and text before
 //- - - - - - - - -//
 text H~2~O
 //- - - - - - - - -//
 <p>text H<sub>2</sub>O</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-9: Tildes in the middle and text after
+8: Tildes in the middle and text after
 //- - - - - - - - -//
 H~2~O text
 //- - - - - - - - -//
 <p>H<sub>2</sub>O text</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
+
+9: Check for a direct conflict with strikethrough
+//- - - - - - - - -//
+~~foobar~~
+//- - - - - - - - -//
+<p><del>foobar</del></p>
+//= = = = = = = = = = = = = = = = = = = = = = = =//
+
+10: Mixed subscript and strikethrough will not work as expected!
+//- - - - - - - - -//
+~~x~foobar~~~
+//- - - - - - - - -//
+<p>~~x~foobar~~~</p>
+//= = = = = = = = = = = = = = = = = = = = = = = =//
diff --git a/extras/_test/superscript.txt b/extras/_test/superscript.txt
@@ -1,4 +1,4 @@
-1: Surrounded by cares
+1: Surrounded by carets
 //- - - - - - - - -//
 ^foo^
 //- - - - - - - - -//
@@ -19,49 +19,42 @@ x^2^ + x^5^
 <p>x<sup>2</sup> + x<sup>5</sup></p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-4: Escaped care
+4: Escaped caret
 //- - - - - - - - -//
 ^foo\^
 //- - - - - - - - -//
 <p>^foo^</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-5: : Cares surround text with a non-breaking space entity
+5: Carets surround text with a non-breaking space entity
 //- - - - - - - - -//
 ^foo&nbsp;bar^
 //- - - - - - - - -//
 <p><sup>foo bar</sup></p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-6: Cares surround text Surround with a non-breaking space (UTF-8)
+6: Carets surround text Surround with a non-breaking space (UTF-8)
 //- - - - - - - - -//
 ^foo bar^
 //- - - - - - - - -//
 <p><sup>foo bar</sup></p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-7: Cares in the middle and text before
+7: Carets in the middle and text before
 //- - - - - - - - -//
 text C^foo^C
 //- - - - - - - - -//
 <p>text C<sup>foo</sup>C</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-8: Cares in the middle and text after
+8: Carets in the middle and text after
 //- - - - - - - - -//
 C^foo^C text
 //- - - - - - - - -//
 <p>C<sup>foo</sup>C text</p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
 
-9: Wrong markers in LaTeX style notation should be left untouched
-//- - - - - - - - -//
-x^2 + x^3
-//- - - - - - - - -//
-<p>x^2 + x^3</p>
-//= = = = = = = = = = = = = = = = = = = = = = = =//
-
-10: Footnote markers should be left untouched
+9: Footnote markers should be left untouched
 //- - - - - - - - -//
 text[^1] text[^2]
 //- - - - - - - - -//

diff --git a/extras/ast.go b/extras/ast.go
@@ -54,6 +54,16 @@ var markTag = inlineTag{
 	RenderPriority:    550,
 }
 
+var deleteTag = inlineTag{
+	TagKind:           kindDelete,
+	Char:              '~',
+	Number:            2,
+	Html:              "del",
+	WhitespaceAllowed: false,
+	ParsePriority:     400,
+	RenderPriority:    400,
+}
+
 type inlineTagNode struct {
 	ast.BaseInline
 
@@ -73,6 +83,7 @@ var (
 	kindSubscript   = ast.NewNodeKind("Subscript")
 	kindInsert      = ast.NewNodeKind("Insert")
 	kindMark        = ast.NewNodeKind("Mark")
+	kindDelete      = ast.NewNodeKind("Delete")
 )
 
 func (n *inlineTagNode) Kind() ast.NodeKind {

diff --git a/extras/inline.go b/extras/inline.go
@@ -48,35 +48,15 @@ func (s *inlineTagParser) Parse(_ ast.Node, block text.Reader, pc parser.Context
 	before := block.PrecendingCharacter()
 	line, segment := block.PeekLine()
 	node := parser.ScanDelimiter(line, before, s.Number, newInlineTagDelimiterProcessor(s.inlineTag))
-	if node == nil {
+	if node == nil || node.OriginalLength > 2 || before == rune(s.Char) {
 		return nil
 	}
-	if !s.WhitespaceAllowed && node.CanOpen && hasSpace(line) {
-		if !(node.CanClose && pc.LastDelimiter() != nil && pc.LastDelimiter().Char == node.Char) {
-			return nil
-		}
-	}
 	node.Segment = segment.WithStop(segment.Start + node.OriginalLength)
 	block.Advance(node.OriginalLength)
 	pc.PushDelimiter(node)
 	return node
 }
 
-// Check if there is an ordinary white space in the line before the next marker
-func hasSpace(line []byte) bool {
-	marker := line[0]
-	for i := 1; i < len(line); i++ {
-		c := line[i]
-		if c == marker {
-			break
-		}
-		if util.IsSpace(c) {
-			return true
-		}
-	}
-	return false
-}
-
 type inlineTagHTMLRenderer struct {
 	htmlTag string
 	tagKind ast.NodeKind
@@ -133,6 +113,7 @@ type Config struct {
 	Subscript   SubscriptConfig
 	Insert      InsertConfig
 	Mark        MarkConfig
+	Delete      DeleteConfig
 }
 
 // SuperscriptConfig configures the superscript extension.
@@ -155,6 +136,10 @@ type MarkConfig struct {
 	Enable bool
 }
 
+type DeleteConfig struct {
+	Enable bool
+}
+
 // New returns a new inline tag extension.
 
 func New(config Config) goldmark.Extender {
@@ -185,4 +170,7 @@ func (tag *inlineExtension) Extend(md goldmark.Markdown) {
 	if tag.conf.Mark.Enable {
 		addTag(markTag)
 	}
+	if tag.conf.Delete.Enable {
+		addTag(deleteTag)
+	}
 }
diff --git a/extras/inline_test.go b/extras/inline_test.go
@@ -5,7 +5,6 @@ import (
 	"testing"
 
 	"github.com/gohugoio/hugo-goldmark-extensions/extras"
-	"github.com/yuin/goldmark/extension"
 	"github.com/yuin/goldmark/text"
 
 	"github.com/yuin/goldmark"
@@ -17,11 +16,17 @@ func buildGoldmarkWithInlineTag(conf extras.Config) goldmark.Markdown {
 }
 
 var (
-	markdown                = goldmark.New()
-	markdownWithSuperscript = buildGoldmarkWithInlineTag(extras.Config{Superscript: extras.SuperscriptConfig{Enable: true}})
-	markdownWithSubscript   = buildGoldmarkWithInlineTag(extras.Config{Subscript: extras.SubscriptConfig{Enable: true}})
-	markdownWithInsert      = buildGoldmarkWithInlineTag(extras.Config{Insert: extras.InsertConfig{Enable: true}})
-	markdownWithMark        = buildGoldmarkWithInlineTag(extras.Config{Mark: extras.MarkConfig{Enable: true}})
+	markdown                       = goldmark.New()
+	markdownWithSuperscript        = buildGoldmarkWithInlineTag(extras.Config{Superscript: extras.SuperscriptConfig{Enable: true}})
+	markdownWithSubscript          = buildGoldmarkWithInlineTag(extras.Config{Subscript: extras.SubscriptConfig{Enable: true}})
+	markdownWithInsert             = buildGoldmarkWithInlineTag(extras.Config{Insert: extras.InsertConfig{Enable: true}})
+	markdownWithMark               = buildGoldmarkWithInlineTag(extras.Config{Mark: extras.MarkConfig{Enable: true}})
+	markdownWithDelete             = buildGoldmarkWithInlineTag(extras.Config{Delete: extras.DeleteConfig{Enable: true}})
+	markdownWithDeleteAndSubscript = goldmark.New(
+		goldmark.WithExtensions(
+			extras.New(extras.Config{Subscript: extras.SubscriptConfig{Enable: true}}),
+			extras.New(extras.Config{Delete: extras.DeleteConfig{Enable: true}}),
+		))
 )
 
 func TestSuperscript(t *testing.T) {
@@ -62,9 +67,7 @@ This formula contains one superscript: f(x) = x^2^ .`
 }
 
 func TestSubscript(t *testing.T) {
-	markdown := goldmark.New(
-		goldmark.WithExtensions(extras.New(extras.Config{Subscript: extras.SubscriptConfig{Enable: true}}), extension.Strikethrough))
-	testutil.DoTestCaseFile(markdown, "_test/subscript.txt", t, testutil.ParseCliCaseArg()...)
+	testutil.DoTestCaseFile(markdownWithDeleteAndSubscript, "_test/subscript.txt", t, testutil.ParseCliCaseArg()...)
 }
 
 func TestSubscriptDump(t *testing.T) {
@@ -175,3 +178,40 @@ Add some marked text: ==marked==. Amazing.`
 		}
 	})
 }
+
+func TestDelete(t *testing.T) {
+	testutil.DoTestCaseFile(markdownWithDelete, "_test/delete.txt", t, testutil.ParseCliCaseArg()...)
+}
+
+func TestDeleteDump(t *testing.T) {
+	input := "Delete some text: ~~deleted~~. Amazing."
+	root := markdownWithDelete.Parser().Parse(text.NewReader([]byte(input)))
+	root.Dump([]byte(input), 0)
+}
+
+func BenchmarkWithAndWithoutDelete(b *testing.B) {
+	const input = `
+## Delete text
+
+Delete some text: ~~deleted~~. Amazing.`
+
+	b.Run("without delete extension", func(b *testing.B) {
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			var buf bytes.Buffer
+			if err := markdown.Convert([]byte(input), &buf); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+
+	b.Run("with delete extension", func(b *testing.B) {
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			var buf bytes.Buffer
+			if err := markdownWithMark.Convert([]byte(input), &buf); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}