Add legacy deserialization blockstore test

ledger/src/blockstore.rs

@@ -5364,7 +5364,7 @@ pub mod tests {
             shred::{max_ticks_per_n_shreds, ShredFlags, LEGACY_SHRED_DATA_CAPACITY},
         },
         assert_matches::assert_matches,
-        bincode::serialize,
+        bincode::{serialize, Options},
         crossbeam_channel::unbounded,
         rand::{seq::SliceRandom, thread_rng},
         solana_account_decoder::parse_token::UiTokenAmount,
@@ -5832,6 +5832,28 @@ pub mod tests {
         test_insert_data_shreds_slots(true);
     }
 
+    #[test]
+    fn test_index_fallback_deserialize() {
+        use rand::Rng;
+        let ledger_path = get_tmp_ledger_path_auto_delete!();
+        let blockstore = Blockstore::open(ledger_path.path()).unwrap();
+        let slot = rand::thread_rng().gen_range(0..100);
+        let bincode = bincode::DefaultOptions::new()
+            .reject_trailing_bytes()
+            .with_fixint_encoding();
+
+        let mut index_v1 = IndexV1::new(slot);
+        index_v1.data_mut().insert(10);
+
+        blockstore
+            .index_cf
+            .put_bytes(slot, &bincode.serialize(&index_v1).unwrap())
+            .unwrap();
+
+        let index_v2 = blockstore.index_cf.get(slot).unwrap().unwrap();
+        assert!(index_v2.data().contains(10))
+    }
+
     /*
         #[test]
         pub fn test_iteration_order() {

ledger/src/blockstore_meta.rs

@@ -110,6 +110,7 @@ mod serde_compat {
 pub type Index = IndexV2;
 pub type ShredIndex = ShredIndexV2;
 pub type IndexFallback = IndexV1;
+pub type ShredIndexFallback = ShredIndexV1;
 
 #[derive(Clone, Debug, Default, Deserialize, Serialize, PartialEq, Eq)]
 /// Index recording presence/absence of shreds
@@ -277,6 +278,32 @@ impl Index {
     }
 }
 
+#[cfg(test)]
+#[allow(unused)]
+impl IndexFallback {
+    pub(crate) fn new(slot: Slot) -> Self {
+        Self {
+            slot,
+            data: ShredIndexFallback::default(),
+            coding: ShredIndexFallback::default(),
+        }
+    }
+
+    pub fn data(&self) -> &ShredIndexFallback {
+        &self.data
+    }
+    pub fn coding(&self) -> &ShredIndexFallback {
+        &self.coding
+    }
+
+    pub(crate) fn data_mut(&mut self) -> &mut ShredIndexFallback {
+        &mut self.data
+    }
+    pub(crate) fn coding_mut(&mut self) -> &mut ShredIndexFallback {
+        &mut self.coding
+    }
+}
+
 /// Superseded by [`ShredIndexV2`].
 ///
 /// TODO: Remove this once new [`ShredIndexV2`] is fully rolled out