Prep v0.16.0 release: allow working with old V9 storage hashers (#68)

* Accomodate a breaking change and allow old V9 storage hashers to work properly

* Prep 0.16.0 release

Author: jsdw

CHANGELOG.md

@@ -4,6 +4,10 @@ The format is based on [Keep a Changelog].
 
 [Keep a Changelog]: http://keepachangelog.com/en/1.0.0/
 
+## 0.16.0 (2025-11-26)
+
+- Add a flag to `StorageInfo` which can be set in order to tell `frame-decode` to use the old version of V9 storage hashers when decoding storage keys. We need to manually toggle this flag when using metadata produced by runtimes prior to [this change](https://github.com/paritytech/substrate/commit/bbb363f4320b4a72e059c0fca96af42296d5a6bf#diff-aa7bc120d701816def0f2a5eb469212d2b7021d2fc9d3b284f843f3f8089e91a), which altered the storage hashers (and thus their encoding/decoding). Kusama prior to spec version 1032 is one such case when this needs to be toggled.
+
 ## 0.15.0 (2025-11-20)
 
 - Update to `scale-info-legacy` 0.4.0.

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "frame-decode"
-version = "0.15.0"
+version = "0.16.0"
 edition = "2024"
 description = "Decode extrinsics and storage from Substrate based chains"
 license = "Apache-2.0"

Cargo.toml

@@ -383,7 +383,12 @@ where
 
     let mut parts = vec![];
     for key in &*storage_info.keys {
-        let hasher = key.hasher;
+        let hasher = if storage_info.use_old_v9_storage_hashers {
+            map_to_old_v9_storage_hashers(key.hasher)
+        } else {
+            key.hasher
+        };
+
         let start_idx = curr_idx(cursor);
         let part = match &hasher {
             StorageHasher::Blake2_128 | StorageHasher::Twox128 => {
@@ -756,6 +761,23 @@ fn strip_bytes<'a, T>(
     Ok(bytes)
 }
 
+fn map_to_old_v9_storage_hashers(hasher: StorageHasher) -> StorageHasher {
+    match hasher {
+        // See https://github.com/paritytech/substrate/commit/bbb363f4320b4a72e059c0fca96af42296d5a6bf#diff-aa7bc120d701816def0f2a5eb469212d2b7021d2fc9d3b284f843f3f8089e91a.
+        // We SCALE decode into the "new" variants seen there, but need to translate back to the old ones, which
+        // is what was actually encoded from the runtime.
+        StorageHasher::Blake2_128 => StorageHasher::Blake2_128,
+        StorageHasher::Blake2_256 => StorageHasher::Blake2_256,
+        StorageHasher::Blake2_128Concat => StorageHasher::Twox128,
+        StorageHasher::Twox128 => StorageHasher::Twox256,
+        StorageHasher::Twox256 => StorageHasher::Twox64Concat,
+
+        // These types didn't exist prior to the change, so just leave them alone:
+        StorageHasher::Twox64Concat => StorageHasher::Twox64Concat,
+        StorageHasher::Identity => StorageHasher::Identity,
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;

src/methods/storage_decoder.rs

@@ -139,15 +139,34 @@ pub struct StorageInfo<'info, TypeId: Clone> {
     pub value_id: TypeId,
     /// Bytes representing the default value for this entry, if one exists.
     pub default_value: Option<Cow<'info, [u8]>>,
+    /// Are we using V9 metadata prior to a change which added a new storage hasher?
+    ///
+    /// See https://github.com/paritytech/substrate/commit/bbb363f4320b4a72e059c0fca96af42296d5a6bf#diff-aa7bc120d701816def0f2a5eb469212d2b7021d2fc9d3b284f843f3f8089e91a
+    /// Here a new hasher is added in the middle of the hashers enum. Thus, Metadata produced
+    /// by V9 runtimes prior to this change will not correctly decode into `frame-metadata`'s V9
+    /// which includes the change.
+    ///
+    /// On Kusama for instance, this should be set to true when using metadata from any spec
+    /// version below 1032 in order to enable decoding correctly from it.
+    pub use_old_v9_storage_hashers: bool,
 }
 
 impl<'info, TypeId: Clone + 'static> StorageInfo<'info, TypeId> {
+    /// For older V9 metadatas, this needs toggling. See the docs on [`StorageInfo::use_old_v9_storage_hashers`].
+    pub fn use_use_old_v9_storage_hashers(self, b: bool) -> Self {
+        StorageInfo {
+            use_old_v9_storage_hashers: b,
+            ..self
+        }
+    }
+
     /// Take ownership of this [`StorageInfo`], turning any lifetimes to `'static`.
     pub fn into_owned(self) -> StorageInfo<'static, TypeId> {
         StorageInfo {
             keys: Cow::Owned(self.keys.into_owned()),
             value_id: self.value_id,
             default_value: self.default_value.map(|v| Cow::Owned(v.into_owned())),
+            use_old_v9_storage_hashers: self.use_old_v9_storage_hashers,
         }
     }
 
@@ -171,6 +190,7 @@ impl<'info, TypeId: Clone + 'static> StorageInfo<'info, TypeId> {
             keys: Cow::Owned(new_keys),
             value_id: new_value_id,
             default_value: self.default_value.map(|d| Cow::Owned(d.into_owned())),
+            use_old_v9_storage_hashers: false,
         })
     }
 }
@@ -253,6 +273,7 @@ macro_rules! impl_storage_type_info_for_v14_to_v16 {
                         keys: Cow::Owned(Vec::new()),
                         value_id: value.id,
                         default_value,
+                        use_old_v9_storage_hashers: false,
                     }),
                     path::StorageEntryType::Map {
                         hashers,
@@ -278,6 +299,7 @@ macro_rules! impl_storage_type_info_for_v14_to_v16 {
                                 }])),
                                 value_id,
                                 default_value,
+                                use_old_v9_storage_hashers: false,
                             })
                         } else if let scale_info::TypeDef::Tuple(tuple) = &key_ty.type_def {
                             // Else, if the key is a tuple, we expect a matching number of hashers
@@ -297,6 +319,7 @@ macro_rules! impl_storage_type_info_for_v14_to_v16 {
                                     keys,
                                     value_id,
                                     default_value,
+                                    use_old_v9_storage_hashers: false,
                                 })
                             } else {
                                 // Hasher and key mismatch
@@ -494,6 +517,7 @@ mod legacy {
                                     keys: Cow::Owned(Vec::new()),
                                     value_id,
                                     default_value,
+                                    use_old_v9_storage_hashers: false,
                                 })
                             }
                             path::StorageEntryType::Map {
@@ -509,6 +533,7 @@ mod legacy {
                                     }])),
                                     value_id,
                                     default_value,
+                                    use_old_v9_storage_hashers: false,
                                 })
                             }
                             path::StorageEntryType::DoubleMap {
@@ -536,6 +561,7 @@ mod legacy {
                                     ])),
                                     value_id,
                                     default_value,
+                                    use_old_v9_storage_hashers: false,
                                 })
                             }
                         }
@@ -668,6 +694,7 @@ mod legacy {
                         keys: Cow::Owned(Vec::new()),
                         value_id,
                         default_value,
+                        use_old_v9_storage_hashers: false,
                     })
                 }
                 frame_metadata::v13::StorageEntryType::Map {
@@ -680,6 +707,7 @@ mod legacy {
                         keys: Cow::Owned(Vec::from_iter([StorageKeyInfo { hasher, key_id }])),
                         value_id,
                         default_value,
+                        use_old_v9_storage_hashers: false,
                     })
                 }
                 frame_metadata::v13::StorageEntryType::DoubleMap {
@@ -707,6 +735,7 @@ mod legacy {
                         ])),
                         value_id,
                         default_value,
+                        use_old_v9_storage_hashers: false,
                     })
                 }
                 frame_metadata::v13::StorageEntryType::NMap {
@@ -749,6 +778,7 @@ mod legacy {
                         keys: Cow::Owned(keys?),
                         value_id,
                         default_value,
+                        use_old_v9_storage_hashers: false,
                     })
                 }
             }