Implement the new fields for plain list.

src/parser/plain_list.rs

@@ -153,6 +153,7 @@ where
     let mut children = Vec::new();
     let mut first_item_indentation: Option<IndentationLevel> = None;
     let mut first_item_list_type: Option<PlainListType> = None;
+    let contents_begin = remaining;
     let mut remaining = remaining;
 
     // The final list item does not consume trailing blank lines (which instead get consumed by the list). We have three options here:
@@ -196,7 +197,8 @@ where
         )));
     }
 
-    let (remaining, _trailing_ws) =
+    let contents = get_consumed(contents_begin, remaining);
+    let (remaining, post_blank) =
         maybe_consume_trailing_whitespace_if_not_exiting(context, remaining)?;
     let source = get_consumed(input, remaining);
     Ok((
@@ -209,6 +211,8 @@ where
             ),
             list_type: first_item_list_type.expect("Plain lists require at least one element."),
             children: children.into_iter().map(|(_start, item)| item).collect(),
+            contents: Some(Into::<&str>::into(contents)),
+            post_blank: post_blank.map(Into::<&str>::into),
         },
     ))
 }

src/types/greater_element.rs

@@ -13,6 +13,8 @@ pub struct PlainList<'s> {
     pub affiliated_keywords: AffiliatedKeywords<'s>,
     pub list_type: PlainListType,
     pub children: Vec<PlainListItem<'s>>,
+    pub contents: Option<&'s str>, // TODO: Can contents ever be None?
+    pub post_blank: Option<&'s str>,
 }
 
 #[derive(Debug, Copy, Clone)]
@@ -142,11 +144,15 @@ impl<'s> StandardProperties<'s> for PlainList<'s> {
     }
 
     fn get_contents<'b>(&'b self) -> Option<&'s str> {
-        todo!()
+        self.contents
     }
 
     fn get_post_blank(&self) -> PostBlank {
-        todo!()
+        self.post_blank
+            .map(|text| text.lines().count())
+            .unwrap_or(0)
+            .try_into()
+            .expect("Too much post-blank to fit into a PostBlank.")
     }
 }