fix(base): null attribute deserializes correctly

also add type address de/serialization tests

base/src/addressing.rs

@@ -103,12 +103,14 @@ impl Address {
             UP_UUID => Ok(Address::Uuid(
                 Uuid::from_slice(digest.as_slice()).map_err(UpEndError::from_any)?,
             )),
-            UP_ATTRIBUTE => Ok(Address::Attribute(
-                String::from_utf8(digest)
-                    .map_err(UpEndError::from_any)?
-                    .as_str()
-                    .parse()?,
-            )),
+            UP_ATTRIBUTE => {
+                let attribute = String::from_utf8(digest).map_err(UpEndError::from_any)?;
+                if attribute.is_empty() {
+                    Ok(Address::Attribute(Attribute::null()))
+                } else {
+                    Ok(Address::Attribute(attribute.parse()?))
+                }
+            }
             UP_URL => Ok(Address::Url(
                 Url::parse(&String::from_utf8(digest).map_err(UpEndError::from_any)?)
                     .map_err(UpEndError::from_any)?,
@@ -255,6 +257,9 @@ mod tests {
     use uuid::Uuid;
 
     use crate::addressing::{Address, IDENTITY};
+    use crate::constants::{
+        TYPE_ATTRIBUTE_ADDRESS, TYPE_HASH_ADDRESS, TYPE_URL_ADDRESS, TYPE_UUID_ADDRESS,
+    };
     use crate::hash::{LargeMultihash, UpMultihash};
 
     use super::UpEndError;
@@ -267,6 +272,11 @@ mod tests {
         let encoded = addr.encode()?;
         let decoded = Address::decode(&encoded)?;
         assert_eq!(addr, decoded);
+
+        let addr = &*TYPE_HASH_ADDRESS;
+        let encoded = addr.encode()?;
+        let decoded = Address::decode(&encoded)?;
+        assert_eq!(addr, &decoded);
         Ok(())
     }
 
@@ -276,6 +286,11 @@ mod tests {
         let encoded = addr.encode()?;
         let decoded = Address::decode(&encoded)?;
         assert_eq!(addr, decoded);
+
+        let addr = &*TYPE_UUID_ADDRESS;
+        let encoded = addr.encode()?;
+        let decoded = Address::decode(&encoded)?;
+        assert_eq!(addr, &decoded);
         Ok(())
     }
 
@@ -285,6 +300,11 @@ mod tests {
         let encoded = addr.encode()?;
         let decoded = Address::decode(&encoded)?;
         assert_eq!(addr, decoded);
+
+        let addr = &*TYPE_ATTRIBUTE_ADDRESS;
+        let encoded = addr.encode()?;
+        let decoded = Address::decode(&encoded)?;
+        assert_eq!(addr, &decoded);
         Ok(())
     }
 
@@ -294,6 +314,11 @@ mod tests {
         let encoded = addr.encode()?;
         let decoded = Address::decode(&encoded)?;
         assert_eq!(addr, decoded);
+
+        let addr = &*TYPE_URL_ADDRESS;
+        let encoded = addr.encode()?;
+        let decoded = Address::decode(&encoded)?;
+        assert_eq!(addr, &decoded);
         Ok(())
     }
 }