feat(extension/tasklist): Preserve TaskList item source positions to …

…allow Tasks to be Accomplished later.

extension/ast/tasklist.go

@@ -2,12 +2,18 @@ package ast
 
 import (
 	"fmt"
+
 	gast "github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
 )
 
 // A TaskCheckBox struct represents a checkbox of a task list.
 type TaskCheckBox struct {
 	gast.BaseInline
+
+	// Segment is a position in a source text.
+	Segment text.Segment
+
 	IsChecked bool
 }
 
@@ -33,3 +39,11 @@ func NewTaskCheckBox(checked bool) *TaskCheckBox {
 		IsChecked: checked,
 	}
 }
+
+// NewTaskCheckBoxSegment returns a new TaskCheckBox node with the given source position.
+func NewTaskCheckBoxSegment(checked bool, segment text.Segment) *TaskCheckBox {
+	return &TaskCheckBox{
+		IsChecked: checked,
+		Segment:   segment,
+	}
+}

extension/tasklist.go

@@ -47,15 +47,16 @@ func (s *taskCheckBoxParser) Parse(parent gast.Node, block text.Reader, pc parse
 	if _, ok := parent.Parent().(*gast.ListItem); !ok {
 		return nil
 	}
-	line, _ := block.PeekLine()
+	line, lineSegment := block.PeekLine()
 	m := taskListRegexp.FindSubmatchIndex(line)
 	if m == nil {
 		return nil
 	}
 	value := line[m[2]:m[3]][0]
 	block.Advance(m[1])
 	checked := value == 'x' || value == 'X'
-	return ast.NewTaskCheckBox(checked)
+	segment := text.NewSegment(lineSegment.Start+m[2], lineSegment.Start+m[3])
+	return ast.NewTaskCheckBoxSegment(checked, segment)
 }
 
 func (s *taskCheckBoxParser) CloseBlock(parent gast.Node, pc parser.Context) {