backend/rpc: Allow older version of the initialized event

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

subxt/src/backend/unstable/rpc_methods.rs

@@ -11,7 +11,7 @@ use crate::config::BlockHash;
 use crate::{Config, Error};
 use derivative::Derivative;
 use futures::{Stream, StreamExt};
-use serde::{Deserialize, Serialize};
+use serde::{Deserialize, Deserializer, Serialize};
 use std::collections::{HashMap, VecDeque};
 use std::task::Poll;
 
@@ -378,8 +378,7 @@ pub enum FollowEvent<Hash> {
 ///
 /// This is the first event generated by the `follow` subscription
 /// and is submitted only once.
-#[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
-#[serde(rename_all = "camelCase")]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Initialized<Hash> {
     /// The hashes of the last finalized blocks.
     pub finalized_block_hashes: Vec<Hash>,
@@ -392,6 +391,30 @@ pub struct Initialized<Hash> {
     pub finalized_block_runtime: Option<RuntimeEvent>,
 }
 
+impl<'de, Hash: Deserialize<'de>> Deserialize<'de> for Initialized<Hash> {
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        // Custom struct that can deserialize both `finalizedBlockHash` and `finalizedBlockHashes`.
+        #[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
+        #[serde(rename_all = "camelCase")]
+        struct InitializedIR<Hash> {
+            finalized_block_hashes: Option<Vec<Hash>>,
+            finalized_block_hash: Option<Hash>,
+            finalized_block_runtime: Option<RuntimeEvent>,
+        }
+
+        let ir = InitializedIR::deserialize(deserializer)?;
+        let finalized_block_hashes = ir
+            .finalized_block_hashes
+            .or_else(|| ir.finalized_block_hash.map(|hash| vec![hash]))
+            .ok_or_else(|| serde::de::Error::custom("Missing finalized block hashes"))?;
+
+        Ok(Initialized {
+            finalized_block_hashes,
+            finalized_block_runtime: ir.finalized_block_runtime,
+        })
+    }
+}
+
 /// The runtime event generated if the `follow` subscription
 /// has set the `with_runtime` flag.
 #[derive(Debug, Clone, PartialEq, Eq, Deserialize)]