Add matching serializer for app_hash field of block::Header struct (

#188)

* Add matching serializer for `app_hash` field of `block::Header` struct

Closes #187

* Add serialization roundtrip test for `block::Header`

tendermint/src/block/header.rs

@@ -59,7 +59,10 @@ pub struct Header {
     pub consensus_hash: Hash,
 
     /// State after txs from the previous block
-    #[serde(deserialize_with = "serializers::parse_hex")]
+    #[serde(
+        serialize_with = "serializers::serialize_hex",
+        deserialize_with = "serializers::parse_hex"
+    )]
     pub app_hash: Vec<u8>,
 
     /// Root hash of all results from the txs from the previous block
@@ -94,3 +97,15 @@ pub struct Version {
     )]
     pub app: u64,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::Header;
+    use crate::test::test_serialization_roundtrip;
+
+    #[test]
+    fn serialization_roundtrip() {
+        let json_data = include_str!("../../tests/support/serialization/block/header.json");
+        test_serialization_roundtrip::<Header>(json_data);
+    }
+}

tendermint/src/lib.rs

@@ -50,6 +50,9 @@ pub mod validator;
 mod version;
 pub mod vote;
 
+#[cfg(test)]
+mod test;
+
 pub use crate::genesis::Genesis;
 pub use crate::{
     block::Block,

tendermint/src/test.rs

@@ -0,0 +1,27 @@
+use serde::{de::DeserializeOwned, Serialize};
+use std::fmt::Debug;
+
+/// Test that a struct `T` can be:
+///
+/// - parsed out of the provided JSON data
+/// - serialized back to JSON
+/// - parsed back from the serialized JSON of the previous step
+/// - that the two parsed structs are equal according to their `PartialEq` impl
+pub fn test_serialization_roundtrip<T>(json_data: &str)
+where
+    T: Debug + PartialEq + Serialize + DeserializeOwned,
+{
+    let parsed0 = serde_json::from_str::<T>(json_data);
+    assert!(parsed0.is_ok());
+    let parsed0 = parsed0.unwrap();
+
+    let serialized = serde_json::to_string(&parsed0);
+    assert!(serialized.is_ok());
+    let serialized = serialized.unwrap();
+
+    let parsed1 = serde_json::from_str::<T>(&serialized);
+    assert!(parsed1.is_ok());
+    let parsed1 = parsed1.unwrap();
+
+    assert_eq!(parsed0, parsed1);
+}

tendermint/tests/support/serialization/block/header.json

@@ -0,0 +1,27 @@
+{
+  "version": {
+    "block": "10",
+    "app": "0"
+  },
+  "chain_id": "cosmoshub-1",
+  "height": "15",
+  "time": "2019-03-13T23:09:34.503701042Z",
+  "num_txs": "2",
+  "total_txs": "4",
+  "last_block_id": {
+    "hash": "42C70F10EF1835CED7248114514B4EF3D06F0D7FD24F6486E3315DEE310D305C",
+    "parts": {
+      "total": "1",
+      "hash": "F51D1B8E6ED859CE23F6B0539E0101653ED4025B13DAA3E76FCC779D5FD96ABE"
+    }
+  },
+  "last_commit_hash": "C499C138BCABA4D40D68A1446F6E5DE1965E07DF17EEACE1A69C1C9B1B8AC5AB",
+  "data_hash": "AC6A27A91A6EF9057D1A33F7944DD9EDD5FC1A3CA49E04EF0801A17FF01B4412",
+  "validators_hash": "EB25B1ACF639219180EB77AFC67E75A51A7CA0D666123E514B6882EC38868652",
+  "next_validators_hash": "EB25B1ACF639219180EB77AFC67E75A51A7CA0D666123E514B6882EC38868652",
+  "consensus_hash": "29C5629148426FB74676BE07F40F2ED79674A67F5833E4C9CCBF759C9372E99C",
+  "app_hash": "0A5826D21A3B0B341C843A0E4946AC787EC9B42A7DC1BEAA344C03C43943B179",
+  "last_results_hash": "",
+  "evidence_hash": "",
+  "proposer_address": "CC05882978FC5FDD6A7721687E14C0299AE004B8"
+}