markup/highlight: Add support to linkable line anchors on Chroma

Fixes #7622

markup/highlight/config.go

@@ -50,6 +50,10 @@ type Config struct {
 	LineNos            bool
 	LineNumbersInTable bool
 
+	// When set, add links to line numbers
+	AnchorLineNos bool
+	LineAnchors   string
+
 	// Start the line numbers from this value (default is 1).
 	LineNoStart int
 
@@ -63,12 +67,17 @@ type Config struct {
 }
 
 func (cfg Config) ToHTMLOptions() []html.Option {
+	var lineAnchors string
+	if cfg.LineAnchors != "" {
+		lineAnchors = cfg.LineAnchors + "-"
+	}
 	var options = []html.Option{
 		html.TabWidth(cfg.TabWidth),
 		html.WithLineNumbers(cfg.LineNos),
 		html.BaseLineNumber(cfg.LineNoStart),
 		html.LineNumbersInTable(cfg.LineNumbersInTable),
 		html.WithClasses(!cfg.NoClasses),
+		html.LinkableLineNumbers(cfg.AnchorLineNos, lineAnchors),
 	}
 
 	if cfg.Hl_Lines != "" {

markup/highlight/highlight_test.go

@@ -79,6 +79,21 @@ User-Agent: foo
 		c.Assert(result, qt.Not(qt.Contains), "class=\"lnt\"")
 	})
 
+	c.Run("Highlight lines, linenumbers default on, anchorlinenumbers default on", func(c *qt.C) {
+		cfg := DefaultConfig
+		cfg.NoClasses = false
+		cfg.LineNos = true
+		cfg.AnchorLineNos = true
+		h := New(cfg)
+
+		result, _ := h.Highlight(lines, "bash", "")
+		c.Assert(result, qt.Contains, "<span class=\"lnt\" id=\"2\">2\n</span>")
+		result, _ = h.Highlight(lines, "bash", "lineanchors=test")
+		c.Assert(result, qt.Contains, "<span class=\"lnt\" id=\"test-2\">2\n</span>")
+		result, _ = h.Highlight(lines, "bash", "anchorlinenos=false,hl_lines=2")
+		c.Assert(result, qt.Not(qt.Contains), "id=\"2\"")
+	})
+
 	c.Run("Highlight lines, linenumbers default on, linenumbers in table default off", func(c *qt.C) {
 		cfg := DefaultConfig
 		cfg.NoClasses = false