Ensure to digest non-empty snapshot_storages and add asserts

runtime/src/bank.rs

@@ -107,6 +107,21 @@ pub struct BankRc {
     pub(crate) slot: Slot,
 }
 
+#[cfg(RUSTC_WITH_SPECIALIZATION)]
+use solana_sdk::abi_example::AbiExample;
+#[cfg(RUSTC_WITH_SPECIALIZATION)]
+impl AbiExample for BankRc {
+    fn example() -> Self {
+        BankRc {
+            // Set parent to None to cut the recursion into another Bank
+            parent: RwLock::new(None),
+            // AbiExample for Accounts is specially implemented to contain a storage example
+            accounts: AbiExample::example(),
+            slot: AbiExample::example(),
+        }
+    }
+}
+
 impl BankRc {
     pub(crate) fn new(accounts: Accounts, slot: Slot) -> Self {
         Self {
@@ -265,7 +280,9 @@ pub(crate) struct BankFieldsToSerialize<'a> {
 }
 
 /// Manager for the state of all accounts and programs after processing its entries.
-#[derive(Default)]
+/// AbiExample is needed even without Serialize/Deserialize; actual (de-)serializeaion
+/// are implemented elsewhere for versioning
+#[derive(Default, AbiExample)]
 pub struct Bank {
     /// References to accounts, parent and signature status
     pub rc: BankRc,

runtime/src/serde_snapshot/tests.rs

@@ -279,28 +279,24 @@ fn test_bank_serialize_older() {
 #[cfg(all(test, RUSTC_WITH_SPECIALIZATION))]
 mod test_bank_serialize {
     use super::*;
-    use solana_sdk::abi_example::AbiExample;
 
     // These some what long test harness is required to freeze the ABI of
     // Bank's serialization due to versioned nature
-    #[frozen_abi(digest = "9BGkhttaVsELn1zoHMKXLvi3Qty51nY1yz584Fao2Ev9")]
-    #[derive(Default, Serialize)]
+    #[frozen_abi(digest = "6MnT4MzuLHe4Uq96YaF3JF2gL1RvprzQHCaV9TaWgYLe")]
+    #[derive(Serialize, AbiExample)]
     pub struct BankAbiTestWrapperFuture {
         #[serde(serialize_with = "wrapper_future")]
         bank: Bank,
     }
 
-    impl AbiExample for BankAbiTestWrapperFuture {
-        fn example() -> Self {
-            Self::default()
-        }
-    }
-
     pub fn wrapper_future<S>(bank: &Bank, s: S) -> std::result::Result<S::Ok, S::Error>
     where
         S: serde::Serializer,
     {
         let snapshot_storages = bank.rc.accounts.accounts_db.get_snapshot_storages(0);
+        // ensure there is a single snapshot storage example for ABI digesting
+        assert_eq!(snapshot_storages.len(), 1);
+
         (SerializableBankAndStorage::<future::Context> {
             bank,
             snapshot_storages: &snapshot_storages,
@@ -309,24 +305,21 @@ mod test_bank_serialize {
         .serialize(s)
     }
 
-    #[frozen_abi(digest = "HYmXta1fhiHe6hZLGJriMqKx9N2U8YRJY51AGZmxzM5m")]
-    #[derive(Default, Serialize)]
+    #[frozen_abi(digest = "92KVEUQ8PwKe5DgZ6AyDQGAi9pvi7kfHdMBE4hcs5EQ4")]
+    #[derive(Serialize, AbiExample)]
     pub struct BankAbiTestWrapperLegacy {
         #[serde(serialize_with = "wrapper_legacy")]
         bank: Bank,
     }
 
-    impl AbiExample for BankAbiTestWrapperLegacy {
-        fn example() -> Self {
-            Self::default()
-        }
-    }
-
     pub fn wrapper_legacy<S>(bank: &Bank, s: S) -> std::result::Result<S::Ok, S::Error>
     where
         S: serde::Serializer,
     {
         let snapshot_storages = bank.rc.accounts.accounts_db.get_snapshot_storages(0);
+        // ensure there is a single snapshot storage example for ABI digesting
+        assert_eq!(snapshot_storages.len(), 1);
+
         (SerializableBankAndStorage::<legacy::Context> {
             bank,
             snapshot_storages: &snapshot_storages,

sdk/src/abi_digester.rs

@@ -340,7 +340,12 @@ impl Serializer for AbiDigester {
     }
 
     fn serialize_seq(mut self, len: Option<usize>) -> DigestResult {
-        self.update_with_string(format!("seq (elements = {})", len.unwrap()));
+        let len = len.unwrap();
+        assert_eq!(
+            len, 1,
+            "Exactly 1 seq element is needed to generate the ABI digest precisely"
+        );
+        self.update_with_string(format!("seq (elements = {})", len));
         Ok(self.create_child())
     }
 
@@ -367,7 +372,12 @@ impl Serializer for AbiDigester {
     }
 
     fn serialize_map(mut self, len: Option<usize>) -> DigestResult {
-        self.update_with_string(format!("map (entries = {})", len.unwrap()));
+        let len = len.unwrap();
+        assert_eq!(
+            len, 1,
+            "Exactly 1 map entry is needed to generate the ABI digest precisely"
+        );
+        self.update_with_string(format!("map (entries = {})", len));
         Ok(self.create_child())
     }