ibc: delete packet commitments instead of writing empty values

The IBC spec calls for deletion of packet commitments after a successful acknowledgement, in order to avoid double-acknowledgements.

Previously, our implementation accomplished this deletion by writing an empty byte slice vec![] to the commitment path.

However, this will cause nonexistence proofs by exclusion (the standard NX-proof type used in ics23) of adjacent keys to fail, since ics23 does not support existence proofs of empty values.

This PR changes `delete_packet_commitment` to actually delete the commitment, and introduces a migration for testnet 78 that will delete all of the previously overwritten commitments.

crates/bin/pd/src/migrate/testnet78.rs

@@ -1,4 +1,5 @@
 //! Contains functions related to the migration script of Testnet78.
+use cnidarium::StateRead;
 use cnidarium::{Snapshot, StateDelta, StateWrite, Storage};
 use futures::TryStreamExt as _;
 use futures::{pin_mut, StreamExt};
@@ -89,6 +90,9 @@ pub async fn migrate(
         // Write the new dex parameters (with the execution budget field) to the state.
         update_dex_params(&mut delta).await?;
 
+        // Migrate empty (deleted) packet commitments to be deleted at the tree level
+        delete_empty_deleted_packet_commitments(&mut delta).await?;
+
         // Reset the application height and halt flag.
         delta.ready_to_start();
         delta.put_block_height(0u64);
@@ -151,6 +155,36 @@ pub async fn migrate(
     Ok(())
 }
 
+async fn delete_empty_deleted_packet_commitments(
+    delta: &mut StateDelta<Snapshot>,
+) -> anyhow::Result<()> {
+    let prefix_key = "ibc-data/commitments/";
+    let stream = delta.prefix_raw(&prefix_key);
+
+    let stream_empty_commitments = stream.filter_map(|entry| async {
+        match entry {
+            Ok((key, val)) => {
+                if val.is_empty() {
+                    Some(key)
+                } else {
+                    None
+                }
+            }
+            Err(e) => {
+                tracing::error!(?e, "error reading packet commitment");
+                None
+            }
+        }
+    });
+    pin_mut!(stream_empty_commitments);
+
+    while let Some(key) = stream_empty_commitments.next().await {
+        delta.delete(key);
+    }
+
+    Ok(())
+}
+
 /// Write the updated dex parameters to the chain state.
 async fn update_dex_params(delta: &mut StateDelta<Snapshot>) -> anyhow::Result<()> {
     let mut dex_params = delta

crates/core/component/ibc/src/component/channel.rs

@@ -81,11 +81,10 @@ pub trait StateWriteExt: StateWrite + StateReadExt {
         port_id: &PortId,
         sequence: u64,
     ) {
-        self.put_raw(
+        self.delete(
             IBC_COMMITMENT_PREFIX.apply_string(
                 CommitmentPath::new(port_id, channel_id, sequence.into()).to_string(),
             ),
-            vec![],
         );
     }