fix: don't set prefix for li element outside list (#45)

Author: wcalandro

testdata/TestCommonmark/list/goldmark.golden

@@ -184,3 +184,4 @@ with two lines.</p>
 <p>before <em>middle</em> after</p>
 </li>
 </ul>
+<p>Not in a list</p>

testdata/TestCommonmark/list/input.html

@@ -163,4 +163,7 @@ <h3>Title</h3>
     <li>before<em>middle</em>after</li>
     <li>before<em>middle</em> after</li>
     <li>before <em>middle</em>after</li>
-</ul>
+</ul>
+
+<!--li not in a list-->
+<li>Not in a list</li>

testdata/TestCommonmark/list/output.asterisks.golden

@@ -102,4 +102,6 @@
 * before _middle_ after
 * before _middle_ after
 * before _middle_ after
-* before _middle_ after
+* before _middle_ after
+
+Not in a list

testdata/TestCommonmark/list/output.dash.golden

@@ -102,4 +102,6 @@
 - before _middle_ after
 - before _middle_ after
 - before _middle_ after
-- before _middle_ after
+- before _middle_ after
+
+Not in a list

testdata/TestCommonmark/list/output.plus.golden

@@ -102,4 +102,6 @@
 + before _middle_ after
 + before _middle_ after
 + before _middle_ after
-+ before _middle_ after
++ before _middle_ after
+
+Not in a list

utils.go

@@ -367,17 +367,19 @@ func getListPrefix(opt *Options, s *goquery.Selection) string {
 	parent := s.Parent()
 	if parent.Is("ul") {
 		return opt.BulletListMarker + " "
-	}
-
-	currentIndex := s.Index() + 1
+	} else if parent.Is("ol") {
+		currentIndex := s.Index() + 1
 
-	lastIndex := parent.Children().Last().Index() + 1
-	maxLength := len(strconv.Itoa(lastIndex))
+		lastIndex := parent.Children().Last().Index() + 1
+		maxLength := len(strconv.Itoa(lastIndex))
 
-	// pad the numbers so that all prefix numbers in the list take up the same space
-	// `%02d.` -> "01. "
-	format := `%0` + strconv.Itoa(maxLength) + `d. `
-	return fmt.Sprintf(format, currentIndex)
+		// pad the numbers so that all prefix numbers in the list take up the same space
+		// `%02d.` -> "01. "
+		format := `%0` + strconv.Itoa(maxLength) + `d. `
+		return fmt.Sprintf(format, currentIndex)
+	}
+	// If the HTML is malformed and the list element isn't in a ul or ol, return no prefix
+	return ""
 }
 
 // countListParents counts how much space is reserved for the prefixes at all the parent lists.