Change Display for ChannelId to avoid allocation, add unit test

Author: optout21

lightning/src/ln/channel.rs

@@ -674,7 +674,7 @@ impl ToHex for ChannelId {
 
 impl fmt::Display for ChannelId {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		f.write_str(&self.to_hex())
+		crate::util::logger::DebugBytes(&self.data).fmt(f)
 	}
 }
 
@@ -7601,6 +7601,12 @@ mod tests {
 		assert_eq!(channel_id_2.bytes(), &data);
 	}
 
+	#[test]
+	fn test_channel_id_display() {
+		let channel_id = ChannelId::from_bytes([42; 32]);
+		assert_eq!(format!("{}", &channel_id), "2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a2a");
+	}
+
 	#[test]
 	fn test_max_funding_satoshis_no_wumbo() {
 		assert_eq!(TOTAL_BITCOIN_SUPPLY_SATOSHIS, 21_000_000 * 100_000_000);