[chore/bugfix] Switch markdown from blackfriday to goldmark (#1267)

Co-authored-by: Autumn! <autumnull@posteo.net>

vendor/github.com/yuin/goldmark/extension/strikethrough.go

@@ -0,0 +1,116 @@
+package extension
+
+import (
+	"github.com/yuin/goldmark"
+	gast "github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/extension/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+type strikethroughDelimiterProcessor struct {
+}
+
+func (p *strikethroughDelimiterProcessor) IsDelimiter(b byte) bool {
+	return b == '~'
+}
+
+func (p *strikethroughDelimiterProcessor) CanOpenCloser(opener, closer *parser.Delimiter) bool {
+	return opener.Char == closer.Char
+}
+
+func (p *strikethroughDelimiterProcessor) OnMatch(consumes int) gast.Node {
+	return ast.NewStrikethrough()
+}
+
+var defaultStrikethroughDelimiterProcessor = &strikethroughDelimiterProcessor{}
+
+type strikethroughParser struct {
+}
+
+var defaultStrikethroughParser = &strikethroughParser{}
+
+// NewStrikethroughParser return a new InlineParser that parses
+// strikethrough expressions.
+func NewStrikethroughParser() parser.InlineParser {
+	return defaultStrikethroughParser
+}
+
+func (s *strikethroughParser) Trigger() []byte {
+	return []byte{'~'}
+}
+
+func (s *strikethroughParser) Parse(parent gast.Node, block text.Reader, pc parser.Context) gast.Node {
+	before := block.PrecendingCharacter()
+	line, segment := block.PeekLine()
+	node := parser.ScanDelimiter(line, before, 2, defaultStrikethroughDelimiterProcessor)
+	if node == nil {
+		return nil
+	}
+	node.Segment = segment.WithStop(segment.Start + node.OriginalLength)
+	block.Advance(node.OriginalLength)
+	pc.PushDelimiter(node)
+	return node
+}
+
+func (s *strikethroughParser) CloseBlock(parent gast.Node, pc parser.Context) {
+	// nothing to do
+}
+
+// StrikethroughHTMLRenderer is a renderer.NodeRenderer implementation that
+// renders Strikethrough nodes.
+type StrikethroughHTMLRenderer struct {
+	html.Config
+}
+
+// NewStrikethroughHTMLRenderer returns a new StrikethroughHTMLRenderer.
+func NewStrikethroughHTMLRenderer(opts ...html.Option) renderer.NodeRenderer {
+	r := &StrikethroughHTMLRenderer{
+		Config: html.NewConfig(),
+	}
+	for _, opt := range opts {
+		opt.SetHTMLOption(&r.Config)
+	}
+	return r
+}
+
+// RegisterFuncs implements renderer.NodeRenderer.RegisterFuncs.
+func (r *StrikethroughHTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(ast.KindStrikethrough, r.renderStrikethrough)
+}
+
+// StrikethroughAttributeFilter defines attribute names which dd elements can have.
+var StrikethroughAttributeFilter = html.GlobalAttributeFilter
+
+func (r *StrikethroughHTMLRenderer) renderStrikethrough(w util.BufWriter, source []byte, n gast.Node, entering bool) (gast.WalkStatus, error) {
+	if entering {
+		if n.Attributes() != nil {
+			_, _ = w.WriteString("<del")
+			html.RenderAttributes(w, n, StrikethroughAttributeFilter)
+			_ = w.WriteByte('>')
+		} else {
+			_, _ = w.WriteString("<del>")
+		}
+	} else {
+		_, _ = w.WriteString("</del>")
+	}
+	return gast.WalkContinue, nil
+}
+
+type strikethrough struct {
+}
+
+// Strikethrough is an extension that allow you to use strikethrough expression like '~~text~~' .
+var Strikethrough = &strikethrough{}
+
+func (e *strikethrough) Extend(m goldmark.Markdown) {
+	m.Parser().AddOptions(parser.WithInlineParsers(
+		util.Prioritized(NewStrikethroughParser(), 500),
+	))
+	m.Renderer().AddOptions(renderer.WithNodeRenderers(
+		util.Prioritized(NewStrikethroughHTMLRenderer(), 500),
+	))
+}