Add support for list item checkboxes (e.g. [X])

see https://orgmode.org/manual/Checkboxes.html
We're deviating from Org mode regarding the assigned css classes but the chosen
classes feel better than (on, off, trans) and it's not like the export matches
1:1 otherwise.

org/html.go

@@ -34,6 +34,12 @@ var listTags = map[string][]string{
 	"descriptive": []string{"<dl>", "</dl>"},
 }
 
+var listItemStatuses = map[string]string{
+	" ": "unchecked",
+	"-": "indeterminate",
+	"X": "checked",
+}
+
 func NewHTMLWriter() *HTMLWriter {
 	return &HTMLWriter{
 		htmlEscape:            true,
@@ -283,13 +289,22 @@ func (w *HTMLWriter) writeList(l List) {
 }
 
 func (w *HTMLWriter) writeListItem(li ListItem) {
-	w.WriteString("<li>\n")
+	if li.Status != "" {
+		w.WriteString(fmt.Sprintf("<li class=\"%s\">\n", listItemStatuses[li.Status]))
+	} else {
+		w.WriteString("<li>\n")
+	}
 	w.writeNodes(li.Children...)
 	w.WriteString("</li>\n")
 }
 
 func (w *HTMLWriter) writeDescriptiveListItem(di DescriptiveListItem) {
-	w.WriteString("<dt>\n")
+	if di.Status != "" {
+		w.WriteString(fmt.Sprintf("<dt class=\"%s\">\n", listItemStatuses[di.Status]))
+	} else {
+		w.WriteString("<dt>\n")
+	}
+
 	if len(di.Term) != 0 {
 		w.writeNodes(di.Term...)
 	} else {

org/list.go

@@ -14,11 +14,13 @@ type List struct {
 
 type ListItem struct {
 	Bullet   string
+	Status   string
 	Children []Node
 }
 
 type DescriptiveListItem struct {
 	Bullet  string
+	Status  string
 	Term    []Node
 	Details []Node
 }
@@ -26,6 +28,7 @@ type DescriptiveListItem struct {
 var unorderedListRegexp = regexp.MustCompile(`^(\s*)([-]|[+]|[*])\s(.*)`)
 var orderedListRegexp = regexp.MustCompile(`^(\s*)(([0-9]+|[a-zA-Z])[.)])\s+(.*)`)
 var descriptiveListItemRegexp = regexp.MustCompile(`\s::(\s|$)`)
+var listItemStatusRegexp = regexp.MustCompile(`\[( |X|-)\]\s`)
 
 func lexList(line string) (token, bool) {
 	if m := unorderedListRegexp.FindStringSubmatch(line); m != nil {
@@ -79,12 +82,16 @@ func (d *Document) parseList(i int, parentStop stopFn) (int, Node) {
 
 func (d *Document) parseListItem(l List, i int, parentStop stopFn) (int, Node) {
 	start, nodes, bullet := i, []Node{}, d.tokens[i].matches[2]
-	minIndent, dterm, content := d.tokens[i].lvl+len(bullet), "", d.tokens[i].content
+	minIndent, dterm, content, status := d.tokens[i].lvl+len(bullet), "", d.tokens[i].content, ""
+	if m := listItemStatusRegexp.FindStringSubmatch(content); m != nil {
+		status, content = m[1], content[len("[ ] "):]
+	}
 	if l.Kind == "descriptive" {
 		if m := descriptiveListItemRegexp.FindStringIndex(content); m != nil {
 			dterm, content = content[:m[0]], content[m[1]:]
 		}
 	}
+
 	d.tokens[i] = tokenize(strings.Repeat(" ", minIndent) + content)
 	stop := func(d *Document, i int) bool {
 		if parentStop(d, i) {
@@ -99,7 +106,7 @@ func (d *Document) parseListItem(l List, i int, parentStop stopFn) (int, Node) {
 		nodes = append(nodes, node)
 	}
 	if l.Kind == "descriptive" {
-		return i - start, DescriptiveListItem{bullet, d.parseInline(dterm), nodes}
+		return i - start, DescriptiveListItem{bullet, status, d.parseInline(dterm), nodes}
 	}
-	return i - start, ListItem{bullet, nodes}
+	return i - start, ListItem{bullet, status, nodes}
 }

org/org.go

@@ -203,6 +203,9 @@ func (w *OrgWriter) writeListItem(li ListItem) {
 	liWriter.writeNodes(li.Children...)
 	content := strings.TrimPrefix(liWriter.String(), liWriter.indent)
 	w.WriteString(w.indent + li.Bullet)
+	if li.Status != "" {
+		w.WriteString(fmt.Sprintf(" [%s]", li.Status))
+	}
 	if len(content) > 0 && content[0] == '\n' {
 		w.WriteString(content)
 	} else {
@@ -212,6 +215,9 @@ func (w *OrgWriter) writeListItem(li ListItem) {
 
 func (w *OrgWriter) writeDescriptiveListItem(di DescriptiveListItem) {
 	w.WriteString(w.indent + di.Bullet)
+	if di.Status != "" {
+		w.WriteString(fmt.Sprintf(" [%s]", di.Status))
+	}
 	indent := w.indent + strings.Repeat(" ", len(di.Bullet)+1)
 	if len(di.Term) != 0 {
 		term := w.nodesAsString(di.Term...)

org/testdata/headlines.html

@@ -2,14 +2,14 @@
 Simple Headline <code class="statistic">[1/2]</code>
 </h1>
 <ul>
-<li>
+<li class="checked">
 <p>
-[X] checked
+checked
 </p>
 </li>
-<li>
+<li class="unchecked">
 <p>
-[ ] unchecked
+unchecked
 </p>
 </li>
 <li>

org/testdata/lists.html

@@ -1,5 +1,5 @@
 <ul>
-<li>
+<li class="unchecked">
 <p>
 unordered list item 1
 </p>
@@ -9,22 +9,22 @@ unordered list item 1
 unordered list item 2 - with <code>inline</code> <em>markup</em>
 </p>
 <ol>
-<li>
+<li class="indeterminate">
 <p>
 ordered sublist item 1
 </p>
 <ol>
-<li>
+<li class="checked">
 <p>
 ordered sublist item 1
 </p>
 </li>
-<li>
+<li class="unchecked">
 <p>
 ordered sublist item 2
 </p>
 </li>
-<li>
+<li class="checked">
 <p>
 ordered sublist item 3
 </p>
@@ -38,7 +38,7 @@ ordered sublist item 2
 </li>
 </ol>
 </li>
-<li>
+<li class="checked">
 <p>
 unordered list item 3 - and a <a href="https://example.com">link</a>
 and some lines of text
@@ -95,20 +95,20 @@ that spans multiple lines
 descriptive lists
 </p>
 <dl>
-<dt>
+<dt class="unchecked">
 term<dd>
 <p>
 details
 continued details
 </p>
 <dd>
-<dt>
+<dt class="unchecked">
 ?<dd>
 <p>
 details without a term
 </p>
 <dd>
-<dt>
+<dt class="checked">
 term<dd>
 <p>
 details on a new line

org/testdata/lists.org

@@ -1,11 +1,11 @@
-- unordered list item 1
+- [ ] unordered list item 1
 - unordered list item 2 - with ~inline~ /markup/
-  1. ordered sublist item 1
-     a) ordered sublist item 1
-     b) ordered sublist item 2
-     c) ordered sublist item 3
+  1. [-] ordered sublist item 1
+     a) [X] ordered sublist item 1
+     b) [ ] ordered sublist item 2
+     c) [X] ordered sublist item 3
   2. ordered sublist item 2
-- unordered list item 3 - and a [[https://example.com][link]]
+- [X] unordered list item 3 - and a [[https://example.com][link]]
   and some lines of text
   1. and another subitem
      #+BEGIN_SRC sh
@@ -24,10 +24,10 @@
 
 
 descriptive lists
-- term :: details
+- [ ] term :: details
           continued details
-- details without a term
-- term ::
+- [ ] details without a term
+- [X] term ::
           details on a new line
 - term ::