Allow empty values in the storage (#6364)

* Allow empty values in the storage

* Bump trie-bench

* Bump trie-bench

substrate/primitives/state-machine/Cargo.toml

@@ -16,7 +16,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 log = "0.4.8"
 parking_lot = "0.10.0"
 hash-db = "0.15.2"
-trie-db = "0.20.1"
+trie-db = "0.21.0"
 trie-root = "0.16.0"
 sp-trie = { version = "2.0.0-rc3", path = "../trie" }
 sp-core = { version = "2.0.0-rc3", path = "../core" }

substrate/primitives/state-machine/src/lib.rs

@@ -1306,4 +1306,40 @@ mod tests {
 		}
 		assert!(!duplicate);
 	}
+
+	#[test]
+	fn set_storage_empty_allowed() {
+		let initial: BTreeMap<_, _> = map![
+			b"aaa".to_vec() => b"0".to_vec(),
+			b"bbb".to_vec() => b"".to_vec()
+		];
+		let mut state = InMemoryBackend::<BlakeTwo256>::from(initial);
+		let backend = state.as_trie_backend().unwrap();
+
+		let mut overlay = OverlayedChanges::default();
+		overlay.set_storage(b"ccc".to_vec(), Some(b"".to_vec()));
+		assert_eq!(overlay.storage(b"ccc"), Some(Some(&[][..])));
+		overlay.commit_prospective();
+		assert_eq!(overlay.storage(b"ccc"), Some(Some(&[][..])));
+		assert_eq!(overlay.storage(b"bbb"), None);
+
+		{
+			let mut offchain_overlay = Default::default();
+			let mut cache = StorageTransactionCache::default();
+			let mut ext = Ext::new(
+				&mut overlay,
+				&mut offchain_overlay,
+				&mut cache,
+				backend,
+				changes_trie::disabled_state::<_, u64>(),
+				None,
+			);
+			assert_eq!(ext.storage(b"bbb"), Some(vec![]));
+			assert_eq!(ext.storage(b"ccc"), Some(vec![]));
+			ext.clear_storage(b"ccc");
+			assert_eq!(ext.storage(b"ccc"), None);
+		}
+		overlay.commit_prospective();
+		assert_eq!(overlay.storage(b"ccc"), Some(None));
+	}
 }

substrate/primitives/state-machine/src/testing.rs

@@ -242,7 +242,7 @@ impl<H, N> sp_externalities::ExtensionStore for TestExternalities<H, N> where
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use sp_core::traits::Externalities;
+	use sp_core::{H256, traits::Externalities};
 	use sp_runtime::traits::BlakeTwo256;
 	use hex_literal::hex;
 
@@ -253,8 +253,8 @@ mod tests {
 		ext.set_storage(b"doe".to_vec(), b"reindeer".to_vec());
 		ext.set_storage(b"dog".to_vec(), b"puppy".to_vec());
 		ext.set_storage(b"dogglesworth".to_vec(), b"cat".to_vec());
-		const ROOT: [u8; 32] = hex!("555d4777b52e9196e3f6373c556cc661e79cd463f881ab9e921e70fc30144bf4");
-		assert_eq!(&ext.storage_root()[..], &ROOT);
+		let root = H256::from(hex!("2a340d3dfd52f5992c6b117e9e45f479e6da5afffafeb26ab619cf137a95aeb8"));
+		assert_eq!(H256::from_slice(ext.storage_root().as_slice()), root);
 	}
 
 	#[test]

substrate/primitives/trie/Cargo.toml

@@ -20,13 +20,13 @@ harness = false
 codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false }
 sp-std = { version = "2.0.0-rc3", default-features = false, path = "../std" }
 hash-db = { version = "0.15.2", default-features = false }
-trie-db = { version = "0.20.1", default-features = false }
+trie-db = { version = "0.21.0", default-features = false }
 trie-root = { version = "0.16.0", default-features = false }
-memory-db = { version = "0.20.0", default-features = false }
+memory-db = { version = "0.21.0", default-features = false }
 sp-core = { version = "2.0.0-rc3", default-features = false, path = "../core" }
 
 [dev-dependencies]
-trie-bench = "0.21.0"
+trie-bench = "0.22.0"
 trie-standardmap = "0.15.2"
 criterion = "0.2.11"
 hex-literal = "0.2.1"

substrate/primitives/trie/src/lib.rs

@@ -51,6 +51,7 @@ pub struct Layout<H>(sp_std::marker::PhantomData<H>);
 
 impl<H: Hasher> TrieLayout for Layout<H> {
 	const USE_EXTENSION: bool = false;
+	const ALLOW_EMPTY: bool = true;
 	type Hash = H;
 	type Codec = NodeCodec<Self::Hash>;
 }