Handle nil in object tree.

src/wasm_test/compare.rs

@@ -566,7 +566,6 @@ fn compare_object_tree<'e, 's, 'w>(
     }
 
     for (emacs_attribute, wasm_attribute) in emacs.iter().zip(wasm_attributes.iter()) {
-        let emacs_attribute = emacs_attribute.as_list()?;
         let wasm_attribute = wasm_attribute
             .as_array()
             .ok_or("Wasm middle layer in object tree should be a list.")?;
@@ -580,6 +579,16 @@ fn compare_object_tree<'e, 's, 'w>(
             ));
             return Ok(result);
         }
+        if let Ok("nil") = emacs_attribute.as_atom() {
+            if let Some(serde_json::Value::Null) = wasm_attribute.first() {
+                if let Some(serde_json::Value::Array(w)) = wasm_attribute.get(1) {
+                    if w.is_empty() {
+                        continue;
+                    }
+                }
+            }
+        }
+        let emacs_attribute = emacs_attribute.as_list()?;
         if let Some(serde_json::Value::Null) = wasm_attribute.first() {
             // If optval is null then the emacs array should only contain 1 value.
             if emacs_attribute.len() != 1 {
@@ -622,19 +631,26 @@ fn compare_object_tree<'e, 's, 'w>(
                 .ok_or("first value in wasm object tree should be a list.")?;
             let emacs_val = emacs_attribute
                 .first()
-                .ok_or("If-statement proves this will be Some.")?
-                .as_list()?;
+                .ok_or("If-statement proves this will be Some.")?;
             let wasm_val = wasm_attribute
                 .get(1)
                 .expect("If-statement proves this will be Some.")
                 .as_array()
                 .ok_or("2nd value in wasm object tree should be a list.")?;
             result.extend(wasm_compare_list(source, emacs_optval, wasm_optval.iter())?)?;
-            result.extend(wasm_compare_list(
-                source,
-                emacs_val.iter(),
-                wasm_val.iter(),
-            )?)?;
+            if let Ok("nil") = emacs_val.as_atom() {
+                result.extend(wasm_compare_list(
+                    source,
+                    std::iter::empty(),
+                    wasm_val.iter(),
+                )?)?;
+            } else {
+                result.extend(wasm_compare_list(
+                    source,
+                    emacs_val.as_list()?.iter(),
+                    wasm_val.iter(),
+                )?)?;
+            }
         }
     }