*: Add Serialize and Deserialize to PeerId gossipsub MessageId and kad Key (#2408)

Co-authored-by: Max Inden <mail@max-inden.de>

core/src/lib.rs

@@ -35,6 +35,9 @@
 //!   define how to upgrade each individual substream to use a protocol.
 //!   See the `upgrade` module.
 
+#[cfg(feature = "serde")]
+extern crate _serde as serde;
+
 mod keys_proto {
     include!(concat!(env!("OUT_DIR"), "/keys_proto.rs"));
 }

core/src/peer_id.rs

@@ -24,6 +24,9 @@ use rand::Rng;
 use std::{convert::TryFrom, fmt, str::FromStr};
 use thiserror::Error;
 
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
 /// Public keys with byte-lengths smaller than `MAX_INLINE_KEY_LENGTH` will be
 /// automatically used as the peer id using an identity multihash.
 const MAX_INLINE_KEY_LENGTH: usize = 42;
@@ -164,6 +167,60 @@ impl From<PeerId> for Vec<u8> {
     }
 }
 
+#[cfg(feature = "serde")]
+impl Serialize for PeerId {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: _serde::Serializer,
+    {
+        if serializer.is_human_readable() {
+            serializer.serialize_str(&self.to_base58())
+        } else {
+            serializer.serialize_bytes(&self.to_bytes()[..])
+        }
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> Deserialize<'de> for PeerId {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        use serde::de::*;
+
+        struct PeerIdVisitor;
+
+        impl<'de> Visitor<'de> for PeerIdVisitor {
+            type Value = PeerId;
+
+            fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                write!(f, "valid peer id")
+            }
+
+            fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+            where
+                E: Error,
+            {
+                PeerId::from_bytes(v).map_err(|_| Error::invalid_value(Unexpected::Bytes(v), &self))
+            }
+
+            fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+            where
+                E: Error,
+            {
+                PeerId::from_str(v).map_err(|_| Error::invalid_value(Unexpected::Str(v), &self))
+            }
+        }
+
+        if deserializer.is_human_readable() {
+            deserializer.deserialize_str(PeerIdVisitor)
+        } else {
+            deserializer.deserialize_bytes(PeerIdVisitor)
+        }
+    }
+}
+
 #[derive(Debug, Error)]
 pub enum ParseError {
     #[error("base-58 decode error: {0}")]