Make automatic storage deposits resistant against changing deposit prices (#12083)

* Require `FixedPointOperand` for Balances

* Delay deposit calculation

* Make refunds pro rata of consumed storage

* Add storage migration

* Fix clippy

* Add liquidity checks

* Fixe delayed deposit limit enforcement

* Defer charges

* Import Vec

* Add try-runtime hooks for migration

* Fix warning

* Adapt to new OnRuntimeUpgrade trait

* Apply suggestions from code review

Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>

* fmt

* Apply suggestions from code review

Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>

* More suggestions from code review

Co-authored-by: Sasha Gryaznov <hi@agryaznov.com>

substrate/frame/contracts/src/storage.rs

@@ -34,31 +34,51 @@ use scale_info::TypeInfo;
 use sp_core::crypto::UncheckedFrom;
 use sp_io::KillStorageResult;
 use sp_runtime::{
-	traits::{Hash, Zero},
+	traits::{Hash, Saturating, Zero},
 	RuntimeDebug,
 };
 use sp_std::{marker::PhantomData, prelude::*};
 
-pub type ContractInfo<T> = RawContractInfo<CodeHash<T>, BalanceOf<T>>;
-
 /// Information for managing an account and its sub trie abstraction.
 /// This is the required info to cache for an account.
 #[derive(Encode, Decode, Clone, PartialEq, Eq, RuntimeDebug, TypeInfo, MaxEncodedLen)]
-pub struct RawContractInfo<CodeHash, Balance> {
+#[scale_info(skip_type_params(T))]
+pub struct ContractInfo<T: Config> {
 	/// Unique ID for the subtree encoded as a bytes vector.
 	pub trie_id: TrieId,
 	/// The code associated with a given account.
-	pub code_hash: CodeHash,
-	/// The amount of balance that is currently deposited to pay for consumed storage.
-	pub storage_deposit: Balance,
+	pub code_hash: CodeHash<T>,
+	/// How many bytes of storage are accumulated in this contract's child trie.
+	pub storage_bytes: u32,
+	/// How many items of storage are accumulated in this contract's child trie.
+	pub storage_items: u32,
+	/// This records to how much deposit the accumulated `storage_bytes` amount to.
+	pub storage_byte_deposit: BalanceOf<T>,
+	/// This records to how much deposit the accumulated `storage_items` amount to.
+	pub storage_item_deposit: BalanceOf<T>,
+	/// This records how much deposit is put down in order to pay for the contract itself.
+	///
+	/// We need to store this information separately so it is not used when calculating any refunds
+	/// since the base deposit can only ever be refunded on contract termination.
+	pub storage_base_deposit: BalanceOf<T>,
 }
 
-impl<CodeHash, Balance> RawContractInfo<CodeHash, Balance> {
+impl<T: Config> ContractInfo<T> {
 	/// Associated child trie unique id is built from the hash part of the trie id.
 	#[cfg(test)]
 	pub fn child_trie_info(&self) -> ChildInfo {
 		child_trie_info(&self.trie_id[..])
 	}
+
+	/// The deposit paying for the accumulated storage generated within the contract's child trie.
+	pub fn extra_deposit(&self) -> BalanceOf<T> {
+		self.storage_byte_deposit.saturating_add(self.storage_item_deposit)
+	}
+
+	/// Same as [`Self::extra_deposit`] but including the base deposit.
+	pub fn total_deposit(&self) -> BalanceOf<T> {
+		self.extra_deposit().saturating_add(self.storage_base_deposit)
+	}
 }
 
 /// Associated child trie unique id is built from the hash part of the trie id.
@@ -178,7 +198,7 @@ where
 				},
 				(None, None) => (),
 			}
-			storage_meter.charge(&diff)?;
+			storage_meter.charge(&diff);
 		}
 
 		match &new_value {
@@ -200,14 +220,21 @@ where
 	pub fn new_contract(
 		account: &AccountIdOf<T>,
 		trie_id: TrieId,
-		ch: CodeHash<T>,
+		code_hash: CodeHash<T>,
 	) -> Result<ContractInfo<T>, DispatchError> {
 		if <ContractInfoOf<T>>::contains_key(account) {
 			return Err(Error::<T>::DuplicateContract.into())
 		}
 
-		let contract =
-			ContractInfo::<T> { code_hash: ch, trie_id, storage_deposit: <BalanceOf<T>>::zero() };
+		let contract = ContractInfo::<T> {
+			code_hash,
+			trie_id,
+			storage_bytes: 0,
+			storage_items: 0,
+			storage_byte_deposit: Zero::zero(),
+			storage_item_deposit: Zero::zero(),
+			storage_base_deposit: Zero::zero(),
+		};
 
 		Ok(contract)
 	}