commonmark: allow configuration of empty href/content behavior

plugin/commonmark/commonmark.go

@@ -76,6 +76,34 @@ func WithHeadingStyle(style headingStyle) OptionFunc {
 	}
 }
 
+// WithLinkEmptyHrefBehavior configures how links with *empty hrefs* are rendered.
+// Take for example:
+//
+//	<a href="">the link content</a>
+//
+// LinkBehaviorRenderAsLink would result in "[the link content]()""
+//
+// LinkBehaviorSkipLink would result in "the link content"
+func WithLinkEmptyHrefBehavior(behavior linkRenderingBehavior) OptionFunc {
+	return func(config *config) {
+		config.LinkEmptyHrefBehavior = behavior
+	}
+}
+
+// WithLinkEmptyContentBehavior configures how links *without content* are rendered.
+// Take for example:
+//
+//	<a href="/page"></a>
+//
+// LinkBehaviorRenderAsLink would result in "[](/page)""
+//
+// LinkBehaviorSkipLink would result in an empty string.
+func WithLinkEmptyContentBehavior(behavior linkRenderingBehavior) OptionFunc {
+	return func(config *config) {
+		config.LinkEmptyContentBehavior = behavior
+	}
+}
+
 // TODO: allow changing the link style once the render logic is implemented
 //
 // "inlined" or "referenced_index" or "referenced_short"

plugin/commonmark/commonmark_test.go

@@ -48,6 +48,7 @@ func TestOptionFunc(t *testing.T) {
 		options  []commonmark.OptionFunc
 		expected string
 	}{
+		// - - - - - - - - - - Italic & Bold - - - - - - - - - - //
 		{
 			desc: "WithEmDelimiter",
 			options: []commonmark.OptionFunc{
@@ -65,6 +66,7 @@ func TestOptionFunc(t *testing.T) {
 			expected: `__bold__`,
 		},
 
+		// - - - - - - - - - - Horizontal Rule - - - - - - - - - - //
 		{
 			desc: "WithHorizontalRule(***)",
 			options: []commonmark.OptionFunc{
@@ -98,6 +100,7 @@ func TestOptionFunc(t *testing.T) {
 			expected: `___`,
 		},
 
+		// - - - - - - - - - - List - - - - - - - - - - //
 		{
 			desc: "WithBulletListMarker(+)",
 			options: []commonmark.OptionFunc{
@@ -124,6 +127,7 @@ func TestOptionFunc(t *testing.T) {
 			expected: "* list a\n\n* list b",
 		},
 
+		// - - - - - - - - - - Code - - - - - - - - - - //
 		{
 			desc: "WithCodeBlockFence",
 			options: []commonmark.OptionFunc{
@@ -133,6 +137,7 @@ func TestOptionFunc(t *testing.T) {
 			expected: "~~~\nhello world\n~~~",
 		},
 
+		// - - - - - - - - - - Heading - - - - - - - - - - //
 		{
 			desc: "WithHeadingStyle(atx)",
 			options: []commonmark.OptionFunc{
@@ -150,6 +155,41 @@ func TestOptionFunc(t *testing.T) {
 			expected: "important\n\\\nheading\n=========",
 		},
 
+		// - - - - - - - - - - Link - - - - - - - - - - //
+		{
+			desc: "WithLinkEmptyHrefBehavior(render)",
+			options: []commonmark.OptionFunc{
+				commonmark.WithLinkEmptyHrefBehavior("render"),
+			},
+			input:    `<a href="">the link content</a>`,
+			expected: "[the link content]()",
+		},
+		{
+			desc: "WithLinkEmptyHrefBehavior(skip)",
+			options: []commonmark.OptionFunc{
+				commonmark.WithLinkEmptyHrefBehavior("skip"),
+			},
+			input:    `<a href="">the link content</a>`,
+			expected: "the link content",
+		},
+		// - - - //
+		{
+			desc: "WithLinkEmptyContentBehavior(render)",
+			options: []commonmark.OptionFunc{
+				commonmark.WithLinkEmptyContentBehavior("render"),
+			},
+			input:    `<a href="/page"></a>`,
+			expected: "[](/page)",
+		},
+		{
+			desc: "WithLinkEmptyContentBehavior(skip)",
+			options: []commonmark.OptionFunc{
+				commonmark.WithLinkEmptyContentBehavior("skip"),
+			},
+			input:    `<a href="/page"></a>`,
+			expected: "",
+		},
+
 		// TODO: handle other link styles
 		// {
 		// 	desc: "WithLinkStyle(LinkInlined)",

plugin/commonmark/options.go

@@ -27,6 +27,15 @@ const (
 	HeadingStyleSetext headingStyle = "setext"
 )
 
+type linkRenderingBehavior string
+
+const (
+	// LinkBehaviorRenderAsLink renders the element as a link
+	LinkBehaviorRenderAsLink linkRenderingBehavior = "render"
+	// LinkBehaviorSkipLink skips link rendering and falls back to the other rules (e.g. paragraph)
+	LinkBehaviorSkipLink linkRenderingBehavior = "skip"
+)
+
 // config to customize the output. You can change stuff like
 // the character that is used for strong text.
 type config struct {
@@ -73,6 +82,9 @@ type config struct {
 	//
 	// default: inlined
 	LinkStyle linkStyle
+
+	LinkEmptyHrefBehavior    linkRenderingBehavior
+	LinkEmptyContentBehavior linkRenderingBehavior
 }
 
 func fillInDefaultConfig(cfg *config) config {
@@ -104,6 +116,12 @@ func fillInDefaultConfig(cfg *config) config {
 		cfg.HeadingStyle = "atx"
 	}
 
+	if cfg.LinkEmptyHrefBehavior == "" {
+		cfg.LinkEmptyHrefBehavior = LinkBehaviorRenderAsLink
+	}
+	if cfg.LinkEmptyContentBehavior == "" {
+		cfg.LinkEmptyContentBehavior = LinkBehaviorRenderAsLink
+	}
 	if cfg.LinkStyle == "" {
 		cfg.LinkStyle = LinkStyleInlined
 	}

plugin/commonmark/render_link.go

@@ -53,6 +53,12 @@ func (c *commonmark) renderLink(ctx converter.Context, w converter.Writer, n *ht
 	href = strings.TrimSpace(href)
 	href = ctx.AssembleAbsoluteURL(ctx, "a", href)
 
+	if href == "" && c.config.LinkEmptyHrefBehavior == LinkBehaviorSkipLink {
+		// There is *no href* for the link. Now we have two options:
+		// Continue rendering as a link OR skip to let other renderers take over.
+		return converter.RenderTryNext
+	}
+
 	title := dom.GetAttributeOr(n, "title", "")
 	title = strings.ReplaceAll(title, "\n", " ")
 
@@ -66,12 +72,14 @@ func (c *commonmark) renderLink(ctx converter.Context, w converter.Writer, n *ht
 	ctx.RenderChildNodes(ctx, &buf, n)
 	content := buf.Bytes()
 
-	if bytes.TrimFunc(content, marker.IsSpace) == nil {
+	if len(bytes.TrimFunc(content, marker.IsSpace)) == 0 {
 		// Fallback to the title
 		content = []byte(l.title)
 	}
-	if bytes.TrimSpace(content) == nil {
-		return converter.RenderSuccess
+	if len(bytes.TrimSpace(content)) == 0 && c.config.LinkEmptyContentBehavior == LinkBehaviorSkipLink {
+		// There is *no content* inside the link. Now we have two options:
+		// Continue rendering as a link OR skip to let other renderers take over.
+		return converter.RenderTryNext
 	}
 
 	if l.href == "" {

plugin/commonmark/testdata/GoldenFiles/link.out.md

@@ -14,6 +14,16 @@
 
 <!--no content-->
 
+[](/no_content)
+
+[](/no_content)
+
+[](/no_content)
+
+[](/no_content)
+
+[](/no_content)
+
 <!--no content but fallback-->
 
 [link title](/no_content "link title")