Add code to compare drawers.

src/compare/diff.rs

@@ -11,6 +11,7 @@ use crate::parser::Paragraph;
 use crate::parser::PlainList;
 use crate::parser::PlainListItem;
 use crate::parser::Section;
+use crate::parser::Drawer;
 
 #[derive(Debug)]
 pub struct DiffResult {
@@ -218,7 +219,7 @@ fn compare_element<'s>(
         Element::GreaterBlock(obj) => compare_greater_block(source, emacs, obj),
         Element::FootnoteDefinition(obj) => compare_footnote_definition(source, emacs, obj),
         Element::Comment(obj) => compare_comment(source, emacs, obj),
-        Element::Drawer(obj) => todo!(),
+        Element::Drawer(obj) => compare_drawer(source, emacs, obj),
     }
 }
 
@@ -497,3 +498,48 @@ fn compare_comment<'s>(
         children: child_status,
     })
 }
+
+fn compare_drawer<'s>(
+    source: &'s str,
+    emacs: &'s Token<'s>,
+    rust: &'s Drawer<'s>,
+) -> Result<DiffResult, Box<dyn std::error::Error>> {
+    let children = emacs.as_list()?;
+    let first_child = children
+        .first()
+        .ok_or("Should have at least one child.")?
+        .as_atom()?;
+    if first_child != "drawer" {
+        return Err("Drawer should correspond to a drawer cell.".into());
+    }
+    let mut child_status = Vec::new();
+    let mut this_status = DiffStatus::Good;
+
+    let attributes_child = children
+        .iter()
+        .nth(1)
+        .ok_or("Should have an attributes child.")?;
+    let attributes_map = attributes_child.as_map()?;
+    let begin = attributes_map
+        .get(":begin")
+        .ok_or("Missing :begin attribute.")?
+        .as_atom()?;
+    let end = attributes_map
+        .get(":end")
+        .ok_or("Missing :end attribute.")?
+        .as_atom()?;
+    let (rust_begin, rust_end) = get_offsets(source, rust);
+    if (rust_begin + 1).to_string() != begin || (rust_end + 1).to_string() != end {
+        this_status = DiffStatus::Bad;
+    }
+
+    for (emacs_child, rust_child) in children.iter().skip(2).zip(rust.children.iter()) {
+        child_status.push(compare_element(source, emacs_child, rust_child)?);
+    }
+
+    Ok(DiffResult {
+        status: this_status,
+        name: "drawer".to_owned(),
+        children: child_status,
+    })
+}