Implement fixed width area.

src/wasm/fixed_width_area.rs

@@ -7,12 +7,14 @@ use super::to_wasm::ToWasm;
 use super::AdditionalProperties;
 use crate::compare::ElispFact;
 use crate::types::FixedWidthArea;
+use crate::types::GetAffiliatedKeywords;
 use crate::wasm::to_wasm::ToWasmStandardProperties;
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct WasmFixedWidthArea {
     #[serde(flatten)]
     pub(crate) additional_properties: AdditionalProperties,
+    pub(crate) value: String,
 }
 
 to_wasm!(
@@ -21,12 +23,19 @@ to_wasm!(
     original,
     wasm_context,
     { WasmAstNode::FixedWidthArea(original) },
-    { "TODO".into() },
+    { "fixed-width".into() },
     {
+        let additional_properties = original
+            .get_affiliated_keywords()
+            .to_wasm(wasm_context.clone())?;
+
+        let value = original.get_value();
+
         Ok((
             Vec::new(),
             WasmFixedWidthArea {
-                additional_properties: AdditionalProperties::default(),
+                additional_properties,
+                value,
             },
         ))
     }

src/wasm_test/compare.rs

@@ -57,6 +57,7 @@ fn compare_json_value<'b, 's>(
         (serde_json::Value::Object(w), Token::TextWithProperties(e)) if is_plain_text(w) => {
             compare_plain_text(source, e, w)
         }
+        (serde_json::Value::Null, Token::Atom("nil")) => Ok(WasmDiffResult::default()),
         (serde_json::Value::Null, Token::Atom(_)) => todo!(),
         (serde_json::Value::Null, Token::List(_)) => todo!(),
         (serde_json::Value::Null, Token::TextWithProperties(_)) => todo!(),
@@ -213,7 +214,7 @@ fn compare_ast_node<'e, 's, 'w>(
             (emacs_standard_properties.post_blank, "post-blank"),
         ] {
             match (emacs_value, wasm_standard_properties.get(wasm_name)) {
-                (None, None) => {}
+                (None, None) | (None, Some(serde_json::Value::Null)) => {}
                 (None, Some(_)) => {
                     layer.status.push(WasmDiffStatus::Bad(
                         format!(