Starting a new macro for comparing fields.

This will help us assert that all fields are tested and that only expected fields are present.

src/compare/macros.rs

@@ -0,0 +1,59 @@
+/// Create iterators for ast nodes where it only has to iterate over children
+macro_rules! compare_properties {
+    ($emacs:expr, $($emacs_field:expr),+) => {
+        {
+            let mut this_status = DiffStatus::Good;
+            let mut message: Option<String> = None;
+            let children = $emacs.as_list()?;
+            let attributes_child = children
+            .iter()
+            .nth(1)
+            .ok_or("Should have an attributes child.")?;
+            let attributes_map = attributes_child.as_map()?;
+            let mut emacs_keys: BTreeSet<&str> = attributes_map.keys().map(|s| *s).collect();
+            $(
+            match $emacs_field {
+                EmacsField::Required(name) if emacs_keys.contains(name) => {
+                    emacs_keys.remove(name);
+                },
+                EmacsField::Optional(name) if emacs_keys.contains(name) => {
+                    emacs_keys.remove(name);
+                },
+                EmacsField::Required(name) => {
+                    this_status = DiffStatus::Bad;
+                    message = Some(format!(
+                        "Emacs token lacks required field: {}",
+                        name
+                    ));
+                },
+                EmacsField::Optional(_name) => {},
+            }
+            ),+
+
+            if !emacs_keys.is_empty() {
+                let unexpected_keys: Vec<&str> = emacs_keys.into_iter().collect();
+                let unexpected_keys = unexpected_keys.join(", ");
+                this_status = DiffStatus::Bad;
+                message = Some(format!(
+                    "Emacs token had extra field(s): {}",
+                    unexpected_keys
+                ));
+            }
+
+            $(
+            println!("{:?}", $emacs_field);
+            ),+
+
+            match this_status {
+                DiffStatus::Good => {
+                    Ok(None)
+                },
+                _ => {
+                    Ok(Some((this_status, message)))
+                }
+            }
+        }
+    };
+}
+
+pub(crate) use compare_properties;