WIP New storage APIs roughly completed, lots of errors still

codegen/src/api/storage.rs

@@ -111,11 +111,11 @@ fn generate_storage_entry_fns(
         .collect();
 
     let pallet_name = pallet.name();
-    let storage_name = storage_entry.name();
-    let Some(storage_hash) = pallet.storage_hash(storage_name) else {
+    let entry_name = storage_entry.name();
+    let Some(storage_hash) = pallet.storage_hash(entry_name) else {
         return Err(CodegenError::MissingStorageMetadata(
             pallet_name.into(),
-            storage_name.into(),
+            entry_name.into(),
         ));
     };
 
@@ -223,7 +223,7 @@ fn generate_storage_entry_fns(
             > {
                 #crate_path::storage::address::StaticAddress::new_static(
                     #pallet_name,
-                    #storage_name,
+                    #entry_name,
                     #keys,
                     [#(#storage_hash,)*]
                 )

core/src/dynamic.rs

@@ -23,7 +23,7 @@ pub use crate::tx::payload::dynamic as tx;
 pub use crate::constants::address::dynamic as constant;
 
 // Lookup storage values dynamically.
-// pub use crate::storage::address::dynamic as storage; // TODO re-add.
+pub use crate::storage::address::dynamic as storage;
 
 // Execute runtime API function call dynamically.
 pub use crate::runtime_api::payload::dynamic as runtime_api_call;

core/src/storage/address.rs

@@ -7,7 +7,7 @@
 use alloc::borrow::Cow;
 use frame_decode::storage::IntoEncodableValues;
 use scale_decode::DecodeAsType;
-use crate::utils::Maybe;
+use crate::utils::{Maybe, YesNoMaybe};
 
 /// A storage address. This allows access to a given storage entry, which can then
 /// be iterated over or fetched from by providing the relevant set of keys, or
@@ -22,7 +22,7 @@ pub trait Address {
     /// Does the address have a default value defined for it.
     /// Set to [`crate::utils::Yes`] to enable APIs which require one,
     /// or [`crate::utils::Maybe`] to enable APIs which allow one
-    type HasDefaultValue;
+    type HasDefaultValue: YesNoMaybe;
     /// Does the address point to a map (as opposed to a plain value)? 
     /// Set to [`crate::utils::Yes`] to enable APIs which require a map,
     /// or [`crate::utils::Maybe`] to enable APIs which allow a map.
@@ -63,6 +63,19 @@ impl<KeyParts, Value, HasDefaultValue, IsMap> StaticAddress<KeyParts, Value, Has
         }
     }
 
+    /// Create a new address.
+    pub fn new(
+        pallet_name: impl Into<Cow<'static, str>>,
+        entry_name: impl Into<Cow<'static, str>>,
+    ) -> Self {
+        Self {
+            pallet_name: pallet_name.into(),
+            entry_name: entry_name.into(),
+            validation_hash: None,
+            marker: core::marker::PhantomData
+        }
+    }
+
     /// Do not validate this storage entry prior to accessing it.
     pub fn unvalidated(mut self) -> Self {
         self.validation_hash = None;
@@ -75,6 +88,7 @@ impl<KeyParts, Value, HasDefaultValue, IsMap> Address
 where
     KeyParts: IntoEncodableValues,
     Value: DecodeAsType,
+    HasDefaultValue: YesNoMaybe,
 {
     type KeyParts = KeyParts;
     type Value = Value;
@@ -95,8 +109,8 @@ where
 }
 
 /// A dynamic address is simply a [`StaticAddress`] which asserts that the
-/// entry could be a map and could have a default value.
-pub type DynamicAddress<KeyParts, Value> = StaticAddress<KeyParts, Value, Maybe, Maybe>;
+/// entry *might* be a map and *might* have a default value.
+pub type DynamicAddress<KeyParts = Vec<scale_value::Value>, Value = scale_value::Value> = StaticAddress<KeyParts, Value, Maybe, Maybe>;
 
 /// Construct a new dynamic storage address. You can define the type of the
 /// storage keys and value yourself here, but have no guarantee that they will
@@ -105,11 +119,6 @@ pub fn dynamic<KeyParts: IntoEncodableValues, Value: DecodeAsType>(
     pallet_name: impl Into<Cow<'static, str>>,
     entry_name: impl Into<Cow<'static, str>>,
 ) -> DynamicAddress<KeyParts, Value> {
-    DynamicAddress::<KeyParts, Value> {
-        pallet_name: pallet_name.into(),
-        entry_name: entry_name.into(),
-        validation_hash: None,
-        marker: core::marker::PhantomData
-    }
+    DynamicAddress::<KeyParts, Value>::new(pallet_name, entry_name)
 }
 

core/src/utils/mod.rs

@@ -13,6 +13,7 @@ mod multi_signature;
 mod static_type;
 mod unchecked_extrinsic;
 mod wrapper_opaque;
+mod yesnomaybe;
 
 use alloc::borrow::ToOwned;
 use alloc::format;
@@ -21,6 +22,7 @@ use alloc::vec::Vec;
 use codec::{Compact, Decode, Encode};
 use derive_where::derive_where;
 
+pub use yesnomaybe::{Yes, No, Maybe, YesNoMaybe};
 pub use account_id::AccountId32;
 pub use account_id20::AccountId20;
 pub use era::Era;
@@ -73,13 +75,6 @@ unsafe impl<T> Sync for PhantomDataSendSync<T> {}
 /// as `BTreeMap` which allows us to easily swap the two during codegen.
 pub type KeyedVec<K, V> = Vec<(K, V)>;
 
-/// A unit marker enum.
-pub enum Yes {}
-/// A unit marker enum.
-pub enum Maybe {}
-/// A unit marker enum.
-pub enum No {}
-
 /// A quick helper to encode some bytes to hex.
 pub fn to_hex(bytes: impl AsRef<[u8]>) -> String {
     format!("0x{}", hex::encode(bytes.as_ref()))

core/src/utils/yesnomaybe.rs

@@ -0,0 +1,31 @@
+// Copyright 2019-2025 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+/// A unit marker enum.
+pub enum Yes {}
+/// A unit marker enum.
+pub enum Maybe {}
+/// A unit marker enum.
+pub enum No {}
+
+/// This is implemented for [`Yes`], [`No`] and [`Maybe`] and
+/// allows us to check at runtime which of these types is present. 
+pub trait YesNoMaybe {
+    /// [`Yes`]
+    fn is_yes() -> bool { false }
+    /// [`No`]
+    fn is_no() -> bool { false }
+    /// [`Maybe`]
+    fn is_maybe() -> bool { false }
+}
+
+impl YesNoMaybe for Yes {
+    fn is_yes() -> bool { true }
+}
+impl YesNoMaybe for No {
+    fn is_no() -> bool { true }
+}
+impl YesNoMaybe for Maybe {
+    fn is_maybe() -> bool { true }
+}

historic/examples/extrinsics.rs

@@ -43,7 +43,7 @@ async fn main() -> Result<(), Error> {
                 println!(
                     "    {}: {}",
                     field.name(),
-                    field.decode::<scale_value::Value>().unwrap()
+                    field.decode_as::<scale_value::Value>().unwrap()
                 );
             }
 
@@ -53,7 +53,7 @@ async fn main() -> Result<(), Error> {
                 extrinsic
                     .call()
                     .fields()
-                    .decode::<scale_value::Composite<_>>()
+                    .decode_as::<scale_value::Composite<_>>()
                     .unwrap()
             );
 
@@ -66,14 +66,14 @@ async fn main() -> Result<(), Error> {
                     println!(
                         "    {}: {}",
                         extension.name(),
-                        extension.decode::<scale_value::Value>().unwrap()
+                        extension.decode_as::<scale_value::Value>().unwrap()
                     );
                 }
 
                 // Or all of them at once:
                 println!(
                     "    All: {}",
-                    extensions.decode::<scale_value::Composite<_>>().unwrap()
+                    extensions.decode_as::<scale_value::Composite<_>>().unwrap()
                 );
             }
         }

historic/examples/storage.rs

@@ -25,8 +25,8 @@ async fn main() -> Result<(), Error> {
             .into_map()?;
 
         // We can see the default value for this entry at this block, if one exists.
-        if let Some(default_value) = account_balances.default() {
-            let default_balance_info = default_value.decode::<scale_value::Value>()?;
+        if let Some(default_value) = account_balances.default_value() {
+            let default_balance_info = default_value.decode_as::<scale_value::Value>()?;
             println!("  Default balance info: {default_balance_info}");
         }
 
@@ -37,7 +37,7 @@ async fn main() -> Result<(), Error> {
         if let Some(entry) = account_balances.fetch((account_id,)).await? {
             // We can decode the value into our generic `scale_value::Value` type, which can
             // represent any SCALE-encoded value, like so:
-            let _balance_info = entry.decode::<scale_value::Value>()?;
+            let _balance_info = entry.decode_as::<scale_value::Value>()?;
 
             // Or, if we know what shape to expect, we can decode the parts of the value that we care
             // about directly into a static type, which is more efficient and allows easy type-safe
@@ -53,7 +53,7 @@ async fn main() -> Result<(), Error> {
                 misc_frozen: u128,
                 fee_frozen: u128,
             }
-            let balance_info = entry.decode::<BalanceInfo>()?;
+            let balance_info = entry.decode_as::<BalanceInfo>()?;
 
             println!(
                 "  Single balance info from {account_id_hex} => free: {} reserved: {} misc_frozen: {} fee_frozen: {}",
@@ -72,21 +72,21 @@ async fn main() -> Result<(), Error> {
         let mut all_balances = account_balances.iter(()).await?.take(10);
         while let Some(entry) = all_balances.next().await {
             let entry = entry?;
-            let key = entry.decode_key()?;
+            let key = entry.key()?;
 
             // Decode the account ID from the key (we know here that we're working
             // with a map which has one value, an account ID, so we just decode that part:
             let account_id = key
                 .part(0)
                 .unwrap()
-                .decode::<[u8; 32]>()?
+                .decode_as::<[u8; 32]>()?
                 .expect("We expect this key to decode into a 32 byte AccountId");
 
             let account_id_hex = hex::encode(account_id);
 
             // Decode these values into our generic scale_value::Value type. Less efficient than
             // defining a static type as above, but easier for the sake of the example.
-            let balance_info = entry.decode_value::<scale_value::Value>()?;
+            let balance_info = entry.value().decode_as::<scale_value::Value>()?;
             println!("  {account_id_hex} => {balance_info}");
         }
     }

historic/src/error.rs

@@ -214,22 +214,22 @@ pub enum ExtrinsicCallError {
 
 #[allow(missing_docs)]
 #[derive(Debug, thiserror::Error)]
-#[error("Storage entry is not a map: pallet {pallet_name}, storage {storage_name}")]
+#[error("Storage entry is not a map: pallet {pallet_name}, storage {entry_name}")]
 pub struct StorageEntryIsNotAMap {
     /// The pallet containing the storage entry that was not found.
     pub pallet_name: String,
     /// The storage entry that was not found.
-    pub storage_name: String,
+    pub entry_name: String,
 }
 
 #[allow(missing_docs)]
 #[derive(Debug, thiserror::Error)]
-#[error("Storage entry is not a plain value: pallet {pallet_name}, storage {storage_name}")]
+#[error("Storage entry is not a plain value: pallet {pallet_name}, storage {entry_name}")]
 pub struct StorageEntryIsNotAPlainValue {
     /// The pallet containing the storage entry that was not found.
     pub pallet_name: String,
     /// The storage entry that was not found.
-    pub storage_name: String,
+    pub entry_name: String,
 }
 
 #[allow(missing_docs)]

historic/src/extrinsics/extrinsic_call.rs

@@ -98,7 +98,7 @@ impl<'extrinsics, 'atblock> ExtrinsicCallFields<'extrinsics, 'atblock> {
     }
 
     /// Attempt to decode the fields into the given type.
-    pub fn decode<T: scale_decode::DecodeAsFields>(&self) -> Result<T, ExtrinsicCallError> {
+    pub fn decode_as<T: scale_decode::DecodeAsFields>(&self) -> Result<T, ExtrinsicCallError> {
         with_info!(&self.info => {
             let cursor = &mut self.bytes();
             let mut fields = &mut info.info.call_data().map(|named_arg| {
@@ -156,7 +156,7 @@ impl<'extrinsics, 'atblock> ExtrinsicCallField<'extrinsics, 'atblock> {
     }
 
     /// Attempt to decode the value of this field into the given type.
-    pub fn decode<T: scale_decode::DecodeAsType>(&self) -> Result<T, ExtrinsicCallError> {
+    pub fn decode_as<T: scale_decode::DecodeAsType>(&self) -> Result<T, ExtrinsicCallError> {
         with_call_field_info!(&self.info => {
             let cursor = &mut &*self.field_bytes;
             let decoded = T::decode_as_type(cursor, info.info.ty().clone(), info.resolver)

historic/src/extrinsics/extrinsic_transaction_extensions.rs

@@ -105,7 +105,7 @@ impl<'extrinsics, 'atblock> ExtrinsicTransactionExtensions<'extrinsics, 'atblock
 
     /// Attempt to decode the transaction extensions into a type where each field name is the name of the transaction
     /// extension and the field value is the decoded extension.
-    pub fn decode<T: scale_decode::DecodeAsFields>(
+    pub fn decode_as<T: scale_decode::DecodeAsFields>(
         &self,
     ) -> Result<T, ExtrinsicTransactionExtensionError> {
         with_extensions_info!(&self.info => {
@@ -189,7 +189,7 @@ impl<'extrinsics, 'atblock> ExtrinsicTransactionExtension<'extrinsics, 'atblock>
     }
 
     /// Decode the bytes for this transaction extension into a type that implements `scale_decode::DecodeAsType`.
-    pub fn decode<T: scale_decode::DecodeAsType>(
+    pub fn decode_as<T: scale_decode::DecodeAsType>(
         &self,
     ) -> Result<T, ExtrinsicTransactionExtensionError> {
         with_extension_info!(&self.info => {

historic/src/storage.rs

@@ -42,14 +42,14 @@ where
     pub fn entry(
         &self,
         pallet_name: impl Into<String>,
-        storage_name: impl Into<String>,
+        entry_name: impl Into<String>,
     ) -> Result<StorageEntryClient<'atblock, Client, T>, StorageError> {
         let pallet_name = pallet_name.into();
-        let storage_name = storage_name.into();
+        let entry_name = entry_name.into();
 
         let storage_info = AnyStorageInfo::new(
             &pallet_name,
-            &storage_name,
+            &entry_name,
             self.client.metadata(),
             self.client.legacy_types(),
         )?;
@@ -58,7 +58,7 @@ where
             Ok(StorageEntryClient::Map(StorageEntryMapClient {
                 client: self.client,
                 pallet_name,
-                storage_name,
+                entry_name,
                 info: storage_info,
                 marker: std::marker::PhantomData,
             }))
@@ -66,7 +66,7 @@ where
             Ok(StorageEntryClient::Plain(StorageEntryPlainClient {
                 client: self.client,
                 pallet_name,
-                storage_name,
+                entry_name,
                 info: storage_info,
                 marker: std::marker::PhantomData,
             }))
@@ -105,7 +105,7 @@ where
     }
 
     /// The storage entry name.
-    pub fn storage_name(&self) -> &str {
+    pub fn entry_name(&self) -> &str {
         &self.entry.storage_entry
     }
 
@@ -143,10 +143,10 @@ where
     }
 
     /// Get the storage entry name.
-    pub fn storage_name(&self) -> &str {
+    pub fn entry_name(&self) -> &str {
         match self {
-            StorageEntryClient::Plain(client) => &client.storage_name,
-            StorageEntryClient::Map(client) => &client.storage_name,
+            StorageEntryClient::Plain(client) => &client.entry_name,
+            StorageEntryClient::Map(client) => &client.entry_name,
         }
     }
 
@@ -168,7 +168,7 @@ where
             StorageEntryClient::Plain(client) => Ok(client),
             StorageEntryClient::Map(_) => Err(StorageEntryIsNotAPlainValue {
                 pallet_name: self.pallet_name().into(),
-                storage_name: self.storage_name().into(),
+                entry_name: self.entry_name().into(),
             }),
         }
     }
@@ -180,18 +180,27 @@ where
         match self {
             StorageEntryClient::Plain(_) => Err(StorageEntryIsNotAMap {
                 pallet_name: self.pallet_name().into(),
-                storage_name: self.storage_name().into(),
+                entry_name: self.entry_name().into(),
             }),
             StorageEntryClient::Map(client) => Ok(client),
         }
     }
+
+    /// Return the default value for this storage entry, if there is one. Returns `None` if there
+    /// is no default value.
+    pub fn default_value(&self) -> Option<StorageValue<'_, 'atblock>> {
+        match self {
+            StorageEntryClient::Plain(client) => client.default_value(),
+            StorageEntryClient::Map(client) => client.default_value(),
+        }
+    }
 }
 
 /// A client for working with a plain storage entry.
 pub struct StorageEntryPlainClient<'atblock, Client, T> {
     client: &'atblock Client,
     pallet_name: String,
-    storage_name: String,
+    entry_name: String,
     info: AnyStorageInfo<'atblock>,
     marker: std::marker::PhantomData<T>,
 }
@@ -207,13 +216,13 @@ where
     }
 
     /// Get the storage entry name.
-    pub fn storage_name(&self) -> &str {
-        &self.storage_name
+    pub fn entry_name(&self) -> &str {
+        &self.entry_name
     }
 
     /// Return the default value for this storage entry, if there is one. Returns `None` if there
     /// is no default value.
-    pub fn default(&self) -> Option<StorageValue<'_, 'atblock>> {
+    pub fn default_value(&self) -> Option<StorageValue<'_, 'atblock>> {
         with_info!(info = &self.info => {
             info.info.default_value.as_ref().map(|default_value| {
                 StorageValue::new(&self.info, default_value.clone())
@@ -227,30 +236,24 @@ where
     T: Config + 'atblock,
     Client: OnlineClientAtBlockT<'atblock, T>,
 {
-    /// Fetch the value for this storage entry.
+    /// Fetch the value for this storage entry. If no value exists and no default value is
+    /// set for this storage entry, then `None` will be returned.
     pub async fn fetch(&self) -> Result<Option<StorageValue<'_, 'atblock>>, StorageError> {
         let key_bytes = self.key();
-        fetch(self.client, &key_bytes)
-            .await
-            .map(|v| v.map(|bytes| StorageValue::new(&self.info, Cow::Owned(bytes))))
-    }
+        let value = fetch(self.client, &key_bytes)
+            .await?
+            .map(|bytes| StorageValue::new(&self.info, Cow::Owned(bytes)))
+            .or_else(|| self.default_value());
 
-    /// Fetch the value for this storage entry as per [`StorageEntryPlainClient::fetch`], but return the default
-    /// value for the storage entry if one exists and the entry does not exist.
-    pub async fn fetch_or_default(
-        &self,
-    ) -> Result<Option<StorageValue<'_, 'atblock>>, StorageError> {
-        self.fetch()
-            .await
-            .map(|option_val| option_val.or_else(|| self.default()))
+        Ok(value)
     }
 
     /// The key for this storage entry.
     pub fn key(&self) -> [u8; 32] {
         let pallet_name = &*self.pallet_name;
-        let storage_name = &*self.storage_name;
+        let entry_name = &*self.entry_name;
 
-        frame_decode::storage::encode_storage_key_prefix(pallet_name, storage_name)
+        frame_decode::storage::encode_storage_key_prefix(pallet_name, entry_name)
     }
 }
 
@@ -258,7 +261,7 @@ where
 pub struct StorageEntryMapClient<'atblock, Client, T> {
     client: &'atblock Client,
     pallet_name: String,
-    storage_name: String,
+    entry_name: String,
     info: AnyStorageInfo<'atblock>,
     marker: std::marker::PhantomData<T>,
 }
@@ -274,13 +277,13 @@ where
     }
 
     /// Get the storage entry name.
-    pub fn storage_name(&self) -> &str {
-        &self.storage_name
+    pub fn entry_name(&self) -> &str {
+        &self.entry_name
     }
 
     /// Return the default value for this storage entry, if there is one. Returns `None` if there
     /// is no default value.
-    pub fn default(&self) -> Option<StorageValue<'_, 'atblock>> {
+    pub fn default_value(&self) -> Option<StorageValue<'_, 'atblock>> {
         with_info!(info = &self.info => {
             info.info.default_value.as_ref().map(|default_value| {
                 StorageValue::new(&self.info, default_value.clone())
@@ -296,7 +299,8 @@ where
 {
     /// Fetch a specific key in this map. If the number of keys provided is not equal
     /// to the number of keys required to fetch a single value from the map, then an error
-    /// will be emitted.
+    /// will be emitted. If no value exists but there is a default value for this storage
+    /// entry, then the default value will be returned. Else, `None` will be returned.
     pub async fn fetch<Keys: IntoEncodableValues>(
         &self,
         keys: Keys,
@@ -313,20 +317,12 @@ where
         }
 
         let key_bytes = self.key(keys)?;
-        fetch(self.client, &key_bytes)
-            .await
-            .map(|v| v.map(|bytes| StorageValue::new(&self.info, Cow::Owned(bytes))))
-    }
+        let value = fetch(self.client, &key_bytes)
+            .await?
+            .map(|bytes| StorageValue::new(&self.info, Cow::Owned(bytes)))
+            .or_else(|| self.default_value());
 
-    /// Fetch a specific key in this map as per [`StorageEntryMapClient::fetch`], but return the default
-    /// value for the storage entry if one exists and the entry was not found.
-    pub async fn fetch_or_default<Keys: IntoEncodableValues>(
-        &self,
-        keys: Keys,
-    ) -> Result<Option<StorageValue<'_, 'atblock>>, StorageError> {
-        self.fetch(keys)
-            .await
-            .map(|option_val| option_val.or_else(|| self.default()))
+        Ok(value)
     }
 
     /// Iterate over the values underneath the provided keys.
@@ -387,14 +383,12 @@ where
     // the key bytes and some metadata about them. Or maybe just fetch_raw and iter_raw.
     fn key<Keys: IntoEncodableValues>(&self, keys: Keys) -> Result<Vec<u8>, StorageError> {
         with_info!(info = &self.info => {
-            let mut key_bytes = Vec::new();
-            frame_decode::storage::encode_storage_key_with_info_to(
+            let key_bytes = frame_decode::storage::encode_storage_key_with_info(
                 &self.pallet_name,
-                &self.storage_name,
+                &self.entry_name,
                 keys,
                 &info.info,
                 info.resolver,
-                &mut key_bytes,
             ).map_err(|e| StorageError::KeyEncodeError { reason: e })?;
             Ok(key_bytes)
         })

historic/src/storage/storage_entry.rs

@@ -1,8 +1,7 @@
 use super::storage_info::AnyStorageInfo;
 use super::storage_key::StorageKey;
 use super::storage_value::StorageValue;
-use crate::error::{StorageKeyError, StorageValueError};
-use scale_decode::DecodeAsType;
+use crate::error::StorageKeyError;
 use std::borrow::Cow;
 
 /// This represents a storage entry, which is a key-value pair in the storage.
@@ -30,11 +29,6 @@ impl<'entry, 'atblock> StorageEntry<'entry, 'atblock> {
         &self.key
     }
 
-    /// Get the raw bytes for this storage entry's value.
-    pub fn value_bytes(&self) -> &[u8] {
-        self.value.bytes()
-    }
-
     /// Consume this storage entry and return the raw bytes for the key and value.
     pub fn into_key_and_value_bytes(self) -> (Vec<u8>, Vec<u8>) {
         (self.key, self.value.into_bytes())
@@ -42,12 +36,12 @@ impl<'entry, 'atblock> StorageEntry<'entry, 'atblock> {
 
     /// Decode the key for this storage entry. This gives back a type from which we can
     /// decode specific parts of the key hash (where applicable).
-    pub fn decode_key(&'_ self) -> Result<StorageKey<'_, 'atblock>, StorageKeyError> {
+    pub fn key(&'_ self) -> Result<StorageKey<'_, 'atblock>, StorageKeyError> {
         StorageKey::new(self.value.info, &self.key)
     }
 
-    /// Decode this storage value.
-    pub fn decode_value<T: DecodeAsType>(&self) -> Result<T, StorageValueError> {
-        self.value.decode::<T>()
+    /// Return the storage value.
+    pub fn value(&self) -> &StorageValue<'entry, 'atblock> {
+        &self.value
     }
 }

historic/src/storage/storage_key.rs

@@ -81,7 +81,7 @@ impl<'entry, 'atblock> StorageKey<'entry, 'atblock> {
     /// Attempt to decode the values contained within this storage key to the `Target` type
     /// provided. This type is typically a tuple of types which each implement [`scale_decode::DecodeAsType`]
     /// and correspond to each of the key types present, in order.
-    pub fn decode<Target: IntoDecodableValues>(&self) -> Result<Target,StorageKeyError> {
+    pub fn decode_as<Target: IntoDecodableValues>(&self) -> Result<Target,StorageKeyError> {
         with_key_info!(info = &self.info => {
             let values = frame_decode::storage::decode_storage_key_values(
                 self.bytes, 
@@ -154,7 +154,7 @@ impl<'key, 'entry, 'atblock> StorageKeyPart<'key, 'entry, 'atblock> {
     /// is available as a part of the key hash, allowing us to decode it into anything
     /// implementing [`scale_decode::DecodeAsType`]. If the key was produced using a
     /// different hasher, this will return `None`.
-    pub fn decode<T: scale_decode::DecodeAsType>(&self) -> Result<Option<T>, StorageKeyError> {
+    pub fn decode_as<T: scale_decode::DecodeAsType>(&self) -> Result<Option<T>, StorageKeyError> {
         with_key_info!(info = &self.info => {
             let part_info = &info.info[self.index];
             let Some(value_info) = part_info.value() else {

historic/src/storage/storage_value.rs

@@ -27,7 +27,7 @@ impl<'entry, 'atblock> StorageValue<'entry, 'atblock> {
     }
 
     /// Decode this storage value.
-    pub fn decode<T: DecodeAsType>(&self) -> Result<T, StorageValueError> {
+    pub fn decode_as<T: DecodeAsType>(&self) -> Result<T, StorageValueError> {
         with_info!(info = &self.info => {
             let cursor = &mut &*self.bytes;
 

metadata/benches/bench.rs

@@ -74,10 +74,10 @@ fn bench_get_storage_hash(c: &mut Criterion) {
         };
 
         for storage in storage_entries.entries() {
-            let storage_name = storage.name();
-            let bench_name = format!("{pallet_name}/{storage_name}");
+            let entry_name = storage.name();
+            let bench_name = format!("{pallet_name}/{entry_name}");
             group.bench_function(&bench_name, |b| {
-                b.iter(|| pallet.storage_hash(storage_name))
+                b.iter(|| pallet.storage_hash(entry_name))
             });
         }
     }

subxt/src/client/online_client.rs

@@ -546,25 +546,34 @@ async fn wait_runtime_upgrade_in_finalized_block<T: Config>(
             Err(err) => return Some(Err(err)),
         };
 
-        let key: Vec<scale_value::Value> = vec![];
-        let addr = crate::dynamic::storage("System", "LastRuntimeUpgrade", key);
+        let addr = crate::dynamic::storage::<(), scale_value::Value>("System", "LastRuntimeUpgrade");
 
-        let chunk = match client.storage().at(block_ref.hash()).fetch(&addr).await {
-            Ok(Some(v)) => v,
-            Ok(None) => {
-                // The storage `system::lastRuntimeUpgrade` should always exist.
-                // <https://github.com/paritytech/polkadot-sdk/blob/master/substrate/frame/system/src/lib.rs#L958>
-                unreachable!("The storage item `system::lastRuntimeUpgrade` should always exist")
-            }
-            Err(e) => return Some(Err(e)),
+        let client_at = client.storage().at(block_ref.hash());
+        let Ok(client) = client_at.entry(addr) else {
+            // The storage `system::lastRuntimeUpgrade` should always exist.
+            // <https://github.com/paritytech/polkadot-sdk/blob/master/substrate/frame/system/src/lib.rs#L958>
+            return Some(Err(Error::Other(
+                "The storage item `system::lastRuntimeUpgrade` should always exist (1)".to_string(),
+            )));
         };
 
-        let scale_val = match chunk.to_value() {
-            Ok(v) => v,
-            Err(e) => return Some(Err(e.into())),
+        let client = client
+            .into_plain()
+            .expect("System.LastRuntimeUpgrade should always be a plain storage entry");
+
+        let value = match client.try_fetch().await {
+            Ok(Some(value)) => value,
+            Ok(None) => return Some(Err(Error::Other(
+                "The storage item `system::lastRuntimeUpgrade` should always exist (2)".to_string(),
+            ))),
+            Err(e) => return Some(Err(e))
         };
 
-        let Some(Ok(spec_version)) = scale_val
+        let value = value
+            .decode_as::<scale_value::Value>()
+            .expect("Should be able to decode anything into scale_value::Value");
+
+        let Some(Ok(spec_version)) = value
             .at("spec_version")
             .and_then(|v| v.as_u128())
             .map(u32::try_from)

subxt/src/lib.rs

@@ -76,7 +76,7 @@ pub mod metadata {
 /// Submit dynamic transactions.
 pub mod dynamic {
     pub use subxt_core::dynamic::{
-        At, DecodedValue, DecodedValueThunk, Value, constant, runtime_api_call, tx, // storage // TODO re-add
+        At, DecodedValue, DecodedValueThunk, Value, constant, runtime_api_call, tx, storage,
         view_function_call,
     };
 }

subxt/src/storage/mod.rs

@@ -6,6 +6,9 @@
 
 mod storage_client;
 mod storage_client_at;
+mod storage_value;
+mod storage_entry;
+mod storage_key;
 
 pub use storage_client::StorageClient;
 pub use storage_client_at::StorageClientAt;

subxt/src/storage/storage_client_at.rs

@@ -4,34 +4,52 @@
 
 use crate::{
     backend::{BackendExt, BlockRef},
-    client::OnlineClientT,
+    client::{OfflineClientT, OnlineClientT},
     config::{Config, HashFor},
     error::{Error, MetadataError, StorageAddressError},
     metadata::DecodeWithMetadata,
+    storage::storage_value::StorageValue,
 };
 use codec::Decode;
 use derive_where::derive_where;
 use futures::StreamExt;
+use scale_info::PortableRegistry;
 use std::{future::Future, marker::PhantomData};
-use subxt_core::storage::address::Address;
-use subxt_core::utils::{Maybe, Yes, No};
+use subxt_core::storage::{address::Address, PrefixOf};
+use subxt_core::utils::{Maybe, Yes, No, YesNoMaybe};
+use subxt_core::Metadata;
+use frame_decode::storage::{IntoEncodableValues, StorageInfo};
+use std::borrow::Cow;
+use scale_decode::DecodeAsType;
+use super::storage_entry::StorageEntry;
 
 /// This is returned from a couple of storage functions.
-pub use crate::backend::StreamOfResults;
+pub use crate::backend::StreamOf;
 
 /// Query the runtime storage.
 #[derive_where(Clone; Client)]
 pub struct StorageClientAt<T: Config, Client> {
     client: Client,
+    metadata: Metadata,
     block_ref: BlockRef<HashFor<T>>,
     _marker: PhantomData<T>,
 }
 
-impl<T: Config, Client> StorageClientAt<T, Client> {
-    /// Create a new [`Storage`]
+impl<T, Client> StorageClientAt<T, Client> 
+where
+    T: Config,
+    Client: OfflineClientT<T>
+{
+    /// Create a new [`StorageClientAt`].
     pub(crate) fn new(client: Client, block_ref: BlockRef<HashFor<T>>) -> Self {
+        // Retrieve and store metadata here so that we can borrow it in
+        // subsequent structs, and thus also borrow storage info and
+        // things that borrow from metadata.
+        let metadata = client.metadata();
+
         Self {
             client,
+            metadata,
             block_ref,
             _marker: PhantomData,
         }
@@ -41,29 +59,34 @@ impl<T: Config, Client> StorageClientAt<T, Client> {
 impl<T, Client> StorageClientAt<T, Client>
 where
     T: Config,
-    Client: OnlineClientT<T>,
+    Client: OfflineClientT<T>,
 {
-    pub fn entry<Addr: Address>(&self, address: Addr) -> Result<StorageEntryClient<T, Client, Addr, Addr::IsMap>, Error> {
+    pub fn entry<Addr: Address>(&'_ self, address: Addr) -> Result<StorageEntryClient<'_, T, Client, Addr, Addr::IsMap>, Error> {
         subxt_core::storage::validate(&address, &self.client.metadata())?;
 
         use frame_decode::storage::StorageTypeInfo;
-        let storage_info = self
+        let types = self.metadata.types();
+        let info = self
             .client
             .metadata()
             .storage_info(address.pallet_name(), address.entry_name())?;
 
-        let value = if storage_info.keys.is_empty() {
+        let value = if info.keys.is_empty() {
             StorageEntryClientValue::Plain(StorageEntryPlainClient { 
                 client: self.client.clone(), 
                 block_ref: self.block_ref.clone(), 
-                address, 
+                address,
+                info,
+                types,
                 _marker: core::marker::PhantomData 
             })
         } else {
             StorageEntryClientValue::Map(StorageEntryMapClient { 
                 client: self.client.clone(), 
                 block_ref: self.block_ref.clone(), 
-                address, 
+                address,
+                info,
+                types,
                 _marker: core::marker::PhantomData 
             })
         };
@@ -75,28 +98,49 @@ where
     }
 }
 
-pub struct StorageEntryClient<T: Config, Client, Addr, IsMap> {
-    value: StorageEntryClientValue<T, Client, Addr>,
+/// This represents a single storage entry (be it a plain value or map) 
+/// and the operations that can be performed on it.
+pub struct StorageEntryClient<'atblock, T: Config, Client, Addr: Address, IsMap> {
+    value: StorageEntryClientValue<'atblock, T, Client, Addr>,
     marker: core::marker::PhantomData<IsMap>,
 }
 
-enum StorageEntryClientValue<T: Config, Client, Addr> {
-    Plain(StorageEntryPlainClient<T, Client, Addr>),
-    Map(StorageEntryMapClient<T, Client, Addr>),
+enum StorageEntryClientValue<'atblock, T: Config, Client, Addr: Address> {
+    Plain(StorageEntryPlainClient<'atblock, T, Client, Addr, Addr::HasDefaultValue>),
+    Map(StorageEntryMapClient<'atblock, T, Client, Addr, Addr::HasDefaultValue>),
 }
 
-impl <T: Config, Client, Addr: Address, IsMap> StorageEntryClient<T, Client, Addr, IsMap> {
+impl <'atblock, T: Config, Client, Addr: Address, IsMap> StorageEntryClient<'atblock, T, Client, Addr, IsMap> {
     pub fn pallet_name(&self) -> &str {
         match &self.value {
-            StorageEntryClientValue::Plain(client) => client.address.pallet_name(),
-            StorageEntryClientValue::Map(client) => client.address.pallet_name(),
+            StorageEntryClientValue::Plain(client) => client.pallet_name(),
+            StorageEntryClientValue::Map(client) => client.pallet_name(),
         }
     }
 
-    pub fn storage_name(&self) -> &str {
+    pub fn entry_name(&self) -> &str {
         match &self.value {
-            StorageEntryClientValue::Plain(client) => client.address.entry_name(),
-            StorageEntryClientValue::Map(client) => client.address.entry_name(),
+            StorageEntryClientValue::Plain(client) => client.entry_name(),
+            StorageEntryClientValue::Map(client) => client.entry_name(),
+        }
+    }
+
+    /// Is the storage entry a plain value?
+    pub fn is_plain(&self) -> bool {
+        matches!(self.value, StorageEntryClientValue::Plain(_))
+    }
+
+    /// Is the storage entry a map?
+    pub fn is_map(&self) -> bool {
+        matches!(self.value, StorageEntryClientValue::Map(_))
+    }
+
+    /// Return the default value for this storage entry, if there is one. Returns `None` if there
+    /// is no default value.
+    pub fn default_value(&self) -> Option<StorageValue<'_, 'atblock, Addr::Value>> {
+        match &self.value {
+            StorageEntryClientValue::Plain(client) => client.default_value(),
+            StorageEntryClientValue::Map(client) => client.default_value(),
         }
     }
 }
@@ -104,11 +148,21 @@ impl <T: Config, Client, Addr: Address, IsMap> StorageEntryClient<T, Client, Add
 // When IsMap = Yes, we have statically asserted that the entry is a map. This can only be false
 // if we skip validation of a static call, and the storage entry, while still present, has changed from
 // plain to map.
-impl <T: Config, Client, Addr: Address> StorageEntryClient<T, Client, Addr, Yes> {
-    pub fn into_map(self) -> StorageEntryMapClient<T, Client, Addr> {
+impl <'atblock, T: Config, Client, Addr: Address> StorageEntryClient<'atblock, T, Client, Addr, Yes> {
+    pub fn into_map(self) -> StorageEntryMapClient<'atblock, T, Client, Addr, Addr::HasDefaultValue> {
         match self.value {
             StorageEntryClientValue::Map(this) => this,
-            StorageEntryClientValue::Plain(_) => panic!("When IsMap = Yes, StorageEntryClient should always be a map.")
+            StorageEntryClientValue::Plain(this) => {
+                tracing::warn!("StorageEntryClient::into_map called on a plain storage value");
+                StorageEntryMapClient {
+                    client: this.client,
+                    block_ref: this.block_ref,
+                    address: this.address,
+                    info: this.info,
+                    types: this.types,
+                    _marker: this._marker
+                }
+            }
         }
     }
 }
@@ -116,54 +170,258 @@ impl <T: Config, Client, Addr: Address> StorageEntryClient<T, Client, Addr, Yes>
 // When IsMap = No, we have statically asserted that the entry is a plain value. This can only be false
 // if we skip validation of a static call, and the storage entry, while still present, has changed from
 // map to plain value.
-impl <T: Config, Client, Addr: Address> StorageEntryClient<T, Client, Addr, No> {
-    pub fn into_plain(self) -> StorageEntryPlainClient<T, Client, Addr> {
+impl <'atblock, T: Config, Client, Addr: Address> StorageEntryClient<'atblock, T, Client, Addr, No> {
+    pub fn into_plain(self) -> StorageEntryPlainClient<'atblock, T, Client, Addr, Addr::HasDefaultValue> {
         match self.value {
-            StorageEntryClientValue::Map(_) => panic!("When IsMap = No, StorageEntryClient should always be a plain value."),
             StorageEntryClientValue::Plain(this) => this,
+            StorageEntryClientValue::Map(this) => {
+                tracing::warn!("StorageEntryClient::into_plain called on a map storage value");
+                StorageEntryPlainClient {
+                    client: this.client,
+                    block_ref: this.block_ref,
+                    address: this.address,
+                    info: this.info,
+                    types: this.types,
+                    _marker: this._marker
+                }
+            }
         }
     }
 }
 
 // Regardless, we can do the "safe" thing and try to convert the entry into a map or plain entry.
-impl <T: Config, Client, Addr: Address> StorageEntryClient<T, Client, Addr, Maybe> {
-    pub fn into_map(self) -> Option<StorageEntryMapClient<T, Client, Addr>> {
+impl <'atblock, T: Config, Client, Addr: Address> StorageEntryClient<'atblock, T, Client, Addr, Maybe> {
+    // TODO: In subxt-historic we return Result, not Option, with "StorageEntryIsNotAMapValue" like err.
+    pub fn into_map(self) -> Option<StorageEntryMapClient<'atblock, T, Client, Addr, Addr::HasDefaultValue>> {
         match self.value {
             StorageEntryClientValue::Map(client) => Some(client),
             StorageEntryClientValue::Plain(_) => None,
         }
     }
 
-    pub fn into_plain(self) -> Option<StorageEntryPlainClient<T, Client, Addr>> {
+    pub fn into_plain(self) -> Option<StorageEntryPlainClient<'atblock, T, Client, Addr, Addr::HasDefaultValue>> {
+        // TODO: In subxt-historic we return Result, not Option, with "StorageEntryIsNotAPlainValue" like err.
         match self.value {
             StorageEntryClientValue::Plain(client) => Some(client),
             StorageEntryClientValue::Map(_) => None,
         }
     }
-
-    pub fn is_plain(&self) -> bool {
-        matches!(self.value, StorageEntryClientValue::Plain(_))
-    }
-
-    pub fn is_map(&self) -> bool {
-        matches!(self.value, StorageEntryClientValue::Map(_))
-    }
 }
 
-pub struct StorageEntryPlainClient<T: Config, Client, Addr> {
+/// This represents a plain storage value at some location.
+pub struct StorageEntryPlainClient<'atblock, T: Config, Client, Addr, HasDefaultValue> {
     client: Client,
     block_ref: BlockRef<HashFor<T>>,
     address: Addr,
-    _marker: PhantomData<T>,
+    info: StorageInfo<'atblock, u32>,
+    types: &'atblock PortableRegistry,
+    _marker: PhantomData<(T, HasDefaultValue)>,
 }
 
-pub struct StorageEntryMapClient<T: Config, Client, Addr> {
+impl <'atblock, T, Client, Addr, HasDefaultValue> StorageEntryPlainClient<'atblock, T, Client, Addr, HasDefaultValue> 
+where
+    T: Config,
+    Addr: Address,
+{
+    /// Get the pallet name.
+    pub fn pallet_name(&self) -> &str {
+        self.address.pallet_name()
+    }
+
+    /// Get the storage entry name.
+    pub fn entry_name(&self) -> &str {
+        self.address.entry_name()
+    }
+
+    /// Return the key used to retrieve this storage value.
+    pub fn key(&self) -> [u8; 32] {
+        frame_decode::storage::encode_storage_key_prefix(
+            self.address.pallet_name(),
+            self.address.entry_name()
+        )
+    }
+
+    /// Return the default value for this storage entry, if there is one. Returns `None` if there
+    /// is no default value.
+    pub fn default_value(&self) -> Option<StorageValue<'_, 'atblock, Addr::Value>> {
+        if let Some(default_bytes) = self.info.default_value.as_deref() {
+            Some(StorageValue::new(&self.info, self.types, Cow::Borrowed(default_bytes)))
+        } else {
+            None
+        }
+    }
+}
+
+// When HasDefaultValue = Yes, we expect there to exist a valid default value and will use that
+// if we fetch an entry and get nothing back.
+impl <'atblock, T, Client, Addr> StorageEntryPlainClient<'atblock, T, Client, Addr, Yes> 
+where
+    T: Config,
+    Addr: Address,
+    Client: OnlineClientT<T>
+{
+    pub async fn fetch(&'_ self) -> Result<StorageValue<'_, 'atblock, Addr::Value>, Error> {
+        let value = self
+            .try_fetch()
+            .await?
+            .unwrap_or_else(|| {
+                let bytes = self.info
+                    .default_value
+                    .as_deref()
+                    .unwrap_or_default()
+                    .to_vec();
+                StorageValue::new(&self.info, self.types, bytes)
+            });
+
+        Ok(value)
+    }
+}
+
+impl <'atblock, T, Client, Addr, HasDefaultValue> StorageEntryPlainClient<'atblock, T, Client, Addr, HasDefaultValue> 
+where
+    T: Config,
+    Addr: Address,
+    Client: OnlineClientT<T>
+{
+    pub async fn try_fetch(&self) -> Result<Option<StorageValue<'_, 'atblock, Addr::Value>>, Error> {
+        let value = self.client
+            .backend()
+            .storage_fetch_value(self.key().to_vec(), self.block_ref.hash())
+            .await?
+            .map(|bytes| StorageValue::new(&self.info, self.types, bytes));
+
+        Ok(value)
+    }
+}
+
+/// This represents a map of storage values at some location.
+pub struct StorageEntryMapClient<'atblock, T: Config, Client, Addr, HasDefaultValue> {
     client: Client,
     block_ref: BlockRef<HashFor<T>>,
     address: Addr,
-    _marker: PhantomData<T>,
+    info: StorageInfo<'atblock, u32>,
+    types: &'atblock PortableRegistry,
+    _marker: PhantomData<(T, HasDefaultValue)>,
 }
 
+impl <'atblock, T, Client, Addr, HasDefaultValue> StorageEntryMapClient<'atblock, T, Client, Addr, HasDefaultValue> 
+where
+    T: Config,
+    Addr: Address,
+{
+    /// Get the pallet name.
+    pub fn pallet_name(&self) -> &str {
+        self.address.pallet_name()
+    }
+
+    /// Get the storage entry name.
+    pub fn entry_name(&self) -> &str {
+        self.address.entry_name()
+    }
+
+    /// Return the default value for this storage entry, if there is one. Returns `None` if there
+    /// is no default value.
+    pub fn default_value(&self) -> Option<StorageValue<'_, 'atblock, Addr::Value>> {
+        if let Some(default_bytes) = self.info.default_value.as_deref() {
+            Some(StorageValue::new(&self.info, self.types, Cow::Borrowed(default_bytes)))
+        } else {
+            None
+        }
+    }
+}
+
+// When HasDefaultValue = Yes, we expect there to exist a valid default value and will use that
+// if we fetch an entry and get nothing back.
+impl <'atblock, T, Client, Addr> StorageEntryMapClient<'atblock, T, Client, Addr, Yes> 
+where
+    T: Config,
+    Addr: Address,
+    Client: OnlineClientT<T>
+{
+    pub async fn fetch(&'_ self, keys: Addr::KeyParts) -> Result<StorageValue<'_, 'atblock, Addr::Value>, Error> {
+        if keys.num_encodable_values() != self.info.keys.len() {
+            // This shouldn't be possible in static cases but if Vec<Value> is keys then we need to be checking.
+            todo!("Error: wrong number of keys provided.")
+        }
+        
+        let value = self
+            .try_fetch(keys)
+            .await?
+            .or_else(|| self.default_value())
+            .unwrap();
+
+        Ok(value)
+    }
+}
+
+impl <'atblock, T, Client, Addr, HasDefaultValue> StorageEntryMapClient<'atblock, T, Client, Addr, HasDefaultValue> 
+where
+    T: Config,
+    Addr: Address,
+    Client: OnlineClientT<T>
+{
+    pub async fn try_fetch(&self, keys: Addr::KeyParts) -> Result<Option<StorageValue<'_, 'atblock, Addr::Value>>, Error> {    
+        if keys.num_encodable_values() != self.info.keys.len() {
+            // This shouldn't be possible in static cases but if Vec<Value> is keys then we need to be checking.
+            todo!("Error: wrong number of keys provided.")
+        }
+
+        let key = frame_decode::storage::encode_storage_key_with_info(
+            self.address.pallet_name(),
+            self.address.entry_name(),
+            keys,
+            &self.info,
+            self.types
+        )?;
+
+        let value = self.client
+            .backend()
+            .storage_fetch_value(key, self.block_ref.hash())
+            .await?
+            .map(|bytes| StorageValue::new(&self.info, self.types, bytes))
+            .or_else(|| self.default_value());
+
+        Ok(value)
+    }
+
+    pub async fn iter<Keys: PrefixOf<Addr::KeyParts>>(&self, keys: Keys) -> Result<StreamOf<Result<StorageEntry<'_, 'atblock, Addr>, Error>>, Error> {
+        if keys.num_encodable_values() != self.info.keys.len() {
+            // This shouldn't be possible in static cases but if Vec<Value> is keys then we need to be checking.
+            todo!("Error: wrong number of keys provided.")
+        }
+
+        let block_hash = self.block_ref.hash();
+        let key_bytes = self.key(keys)?;
+        let info = &self.info;
+        let types = self.types;
+
+        let stream = self.client
+            .backend()
+            .storage_fetch_descendant_values(key_bytes, block_hash)
+            .await?
+            .map(|kv| {
+                let kv = match kv {
+                    Ok(kv) => kv,
+                    Err(e) => return Err(e),
+                };
+
+                Ok(StorageEntry::new(info, types, kv.key, Cow::Owned(kv.value)))
+            });
+
+        Ok(StreamOf::new(Box::pin(stream)))
+    }
+
+    fn key<Keys: PrefixOf<Addr::KeyParts>>(&self, keys: Keys) -> Result<Vec<u8>, Error> {
+        let key_bytes = frame_decode::storage::encode_storage_key_with_info(
+            &self.address.pallet_name(),
+            &self.address.entry_name(),
+            keys,
+            &self.info,
+            self.types,
+        )?;
+        Ok(key_bytes)
+    }
+}
 
 /*
 impl<T, Client> Storage<T, Client>

subxt/src/storage/storage_entry.rs

@@ -0,0 +1,53 @@
+// Copyright 2019-2025 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use super::storage_value::StorageValue;
+use super::storage_key::StorageKey;
+use subxt_core::storage::address::Address;
+use frame_decode::storage::StorageInfo;
+use scale_info::PortableRegistry;
+use std::borrow::Cow;
+
+/// This represents a storage entry, which is a key-value pair in the storage.
+pub struct StorageEntry<'entry, 'atblock, Addr: Address> {
+    key: Vec<u8>,
+    // This contains the storage information already:
+    value: StorageValue<'entry, 'atblock, Addr::Value>,
+}
+
+impl<'entry, 'atblock, Addr: Address> StorageEntry<'entry, 'atblock, Addr> {
+    /// Create a new storage entry.
+    pub fn new(
+        info: &'entry StorageInfo<'atblock, u32>,
+        types: &'atblock PortableRegistry,
+        key: Vec<u8>,
+        value: Cow<'atblock, [u8]>,
+    ) -> Self {
+        Self {
+            key,
+            value: StorageValue::new(info, types, value),
+        }
+    }
+
+    /// Get the raw bytes for this storage entry's key.
+    pub fn key_bytes(&self) -> &[u8] {
+        &self.key
+    }
+
+    /// Consume this storage entry and return the raw bytes for the key and value.
+    pub fn into_key_and_value_bytes(self) -> (Vec<u8>, Vec<u8>) {
+        (self.key, self.value.into_bytes())
+    }
+
+    /// Decode the key for this storage entry. This gives back a type from which we can
+    /// decode specific parts of the key hash (where applicable).
+    pub fn key(&'_ self) -> Result<StorageKey<'_, 'atblock, Addr::KeyParts>, StorageKeyError> {
+        StorageKey::new(self.value.info, self.value.types, &self.key)
+    }
+
+    /// Return the storage value.
+    pub fn value(&self) -> &StorageValue<'entry, 'atblock, Addr::Value> {
+        &self.value
+    }
+}

subxt/src/storage/storage_key.rs

@@ -0,0 +1,140 @@
+// Copyright 2019-2025 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use frame_decode::storage::{StorageInfo, StorageKey as StorageKeyPartInfo, IntoDecodableValues};
+use scale_info::PortableRegistry;
+use core::marker::PhantomData;
+
+pub use frame_decode::storage::StorageHasher;
+
+/// This represents the different parts of a storage key.
+pub struct StorageKey<'entry, 'atblock, KeyParts> {
+    info: StorageKeyPartInfo<u32>,
+    types: &'atblock PortableRegistry,
+    bytes: &'entry [u8],
+    marker: PhantomData<KeyParts>
+}
+
+impl<'entry, 'atblock, KeyParts: IntoDecodableValues> StorageKey<'entry, 'atblock, KeyParts> {
+    pub(crate) fn new(
+        info: &StorageInfo<'atblock, u32>,
+        types: &'atblock PortableRegistry,
+        bytes: &'entry [u8],
+    ) -> Result<Self, StorageKeyError> {
+        let cursor = &mut &*bytes;
+        let storage_key_info = frame_decode::storage::decode_storage_key_with_info(
+            cursor,
+            &info,
+            types,
+        ).map_err(|e| {
+            StorageKeyError::DecodeError { reason: e.map_type_id(|id| id.to_string()) }
+        })?;
+
+        if !cursor.is_empty() {
+            return Err(StorageKeyError::LeftoverBytes {
+                leftover_bytes: cursor.to_vec(),
+            });
+        }
+
+        Ok(StorageKey {
+            info: storage_key_info,
+            types,
+            bytes,
+            marker: PhantomData
+        })
+    }
+
+    /// Attempt to decode the values contained within this storage key. The target type is
+    /// given by the storage address used to access this entry. To decode into a custom type,
+    /// use [`Self::parts()`] or [`Self::part()`] and decode each part.
+    pub fn decode(&self) -> Result<KeyParts,StorageKeyError> {
+        let values = frame_decode::storage::decode_storage_key_values(
+            self.bytes, 
+            &self.info, 
+            self.types
+        ).map_err(|e| {
+            StorageKeyError::DecodeKeyValueError { reason: e }
+        })?;
+
+        Ok(values)
+    }
+
+    /// Iterate over the parts of this storage key. Each part of a storage key corresponds to a
+    /// single value that has been hashed.
+    pub fn parts(&'_ self) -> impl ExactSizeIterator<Item = StorageKeyPart<'_, 'entry, 'atblock>> {
+        let parts_len = self.info.parts().len();
+        (0..parts_len).map(move |index| StorageKeyPart {
+            index,
+            info: &self.info,
+            types: self.types,
+            bytes: self.bytes,
+        })
+    }
+
+    /// Return the part of the storage key at the provided index, or `None` if the index is out of bounds.
+    pub fn part(&self, index: usize) -> Option<StorageKeyPart<'_, 'entry, 'atblock>> {
+        if index < self.parts().len() {
+            Some(StorageKeyPart {
+                index,
+                info: &self.info,
+                types: self.types,
+                bytes: self.bytes,
+            })
+        } else {
+            None
+        }
+    }
+}
+
+/// This represents a part of a storage key.
+pub struct StorageKeyPart<'key, 'entry, 'atblock> {
+    index: usize,
+    info: &'key StorageKeyPartInfo<u32>,
+    types: &'atblock PortableRegistry,
+    bytes: &'entry [u8],
+}
+
+impl<'key, 'entry, 'atblock> StorageKeyPart<'key, 'entry, 'atblock> {
+    /// Get the raw bytes for this part of the storage key.
+    pub fn bytes(&self) -> &'entry [u8] {
+        let part = &self.info[self.index];
+        let hash_range = part.hash_range();
+        let value_range = part
+            .value()
+            .map(|v| v.range())
+            .unwrap_or(std::ops::Range { start: hash_range.end, end: hash_range.end });
+        let combined_range = std::ops::Range {
+            start: hash_range.start,
+            end: value_range.end,
+        };
+        &self.bytes[combined_range]
+    }
+
+    /// Get the hasher that was used to construct this part of the storage key.
+    pub fn hasher(&self) -> StorageHasher {
+        self.info[self.index].hasher()
+    }
+
+    /// For keys that were produced using "concat" or "identity" hashers, the value
+    /// is available as a part of the key hash, allowing us to decode it into anything
+    /// implementing [`scale_decode::DecodeAsType`]. If the key was produced using a
+    /// different hasher, this will return `None`.
+    pub fn decode_as<T: scale_decode::DecodeAsType>(&self) -> Result<Option<T>, StorageKeyError> {
+        let part_info = &self.info[self.index];
+        let Some(value_info) = part_info.value() else {
+            return Ok(None);
+        };
+
+        let value_bytes = &self.bytes[value_info.range()];
+        let value_ty = value_info.ty().clone();
+
+        let decoded_key_part = T::decode_as_type(
+            &mut &*value_bytes,
+            value_ty,
+            self.types,
+        ).map_err(|e| StorageKeyError::DecodePartError { index: self.index, reason: e })?;
+
+        Ok(Some(decoded_key_part))
+    }
+}

subxt/src/storage/storage_value.rs

@@ -0,0 +1,62 @@
+// Copyright 2019-2025 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use frame_decode::storage::StorageInfo;
+use scale_decode::DecodeAsType;
+use scale_info::PortableRegistry;
+use core::marker::PhantomData;
+use std::borrow::Cow;
+
+use crate::Error;
+
+/// This represents a storage value.
+pub struct StorageValue<'entry, 'atblock, Value> {
+    pub(crate) info: &'entry StorageInfo<'atblock, u32>,
+    pub(crate) types: &'atblock PortableRegistry,
+    bytes: Cow<'entry, [u8]>,
+    marker: PhantomData<Value>
+}
+
+impl<'entry, 'atblock, Value: DecodeAsType> StorageValue<'entry, 'atblock, Value> {
+    /// Create a new storage value.
+    pub fn new(
+        info: &'entry StorageInfo<'atblock, u32>,
+        types: &'atblock PortableRegistry,
+        bytes: impl Into<Cow<'entry, [u8]>>,
+    ) -> Self {
+        Self { info, types, bytes: bytes.into(), marker: PhantomData }
+    }
+
+    /// Get the raw bytes for this storage value.
+    pub fn bytes(&self) -> &[u8] {
+        &self.bytes
+    }
+
+    /// Consume this storage value and return the raw bytes.
+    pub fn into_bytes(self) -> Vec<u8> {
+        self.bytes.to_vec()
+    }
+
+    /// Decode this storage value into the provided response type.
+    pub fn decode(&self) -> Result<Value, Error> {
+        self.decode_as::<Value>()
+    }
+
+    /// Decode this storage value into an arbitrary type.
+    pub fn decode_as<T: DecodeAsType>(&self) -> Result<T, Error> {
+        let cursor = &mut &*self.bytes;
+
+        let value = T::decode_as_type(
+            cursor,
+            self.info.value_id,
+            self.types,
+        ).map_err(|e| todo!("Define proper errors"))?;
+
+        if !cursor.is_empty() {
+            return Err(todo!("Define proper errors"));
+        }
+
+        Ok(value)
+    }
+}