Client provide uncles (#1609)

* feat: add children function to backend

* feat: add test for children hashes

* feat: add uncles function to client

* fix: improve uncles function adds few more tests

* fix: remove children when reverting

* fix: typo and spec version

substrate/core/test-client/src/trait_tests.rs

@@ -144,6 +144,96 @@ pub fn test_leaves_for_backend<B: 'static>(backend: Arc<B>) where
 		vec![a5.hash(), b4.hash(), c3.hash(), d2.hash()]);
 }
 
+/// helper to test the `children` implementation for various backends
+pub fn test_children_for_backend<B: 'static>(backend: Arc<B>) where
+	B: backend::LocalBackend<runtime::Block, Blake2Hasher>,
+{
+	// block tree:
+	// G -> A1 -> A2 -> A3 -> A4 -> A5
+	//		A1 -> B2 -> B3 -> B4
+	//			  B2 -> C3
+	//		A1 -> D2
+
+	let client = new_with_backend(backend.clone(), false);
+
+	// G -> A1
+	let a1 = client.new_block().unwrap().bake().unwrap();
+	client.import(BlockOrigin::Own, a1.clone()).unwrap();
+
+	// A1 -> A2
+	let a2 = client.new_block_at(&BlockId::Hash(a1.hash())).unwrap().bake().unwrap();
+	client.import(BlockOrigin::Own, a2.clone()).unwrap();
+
+	// A2 -> A3
+	let a3 = client.new_block_at(&BlockId::Hash(a2.hash())).unwrap().bake().unwrap();
+	client.import(BlockOrigin::Own, a3.clone()).unwrap();
+
+	// A3 -> A4
+	let a4 = client.new_block_at(&BlockId::Hash(a3.hash())).unwrap().bake().unwrap();
+	client.import(BlockOrigin::Own, a4.clone()).unwrap();
+
+	// A4 -> A5
+	let a5 = client.new_block_at(&BlockId::Hash(a4.hash())).unwrap().bake().unwrap();
+	client.import(BlockOrigin::Own, a5.clone()).unwrap();
+
+	// A1 -> B2
+	let mut builder = client.new_block_at(&BlockId::Hash(a1.hash())).unwrap();
+	// this push is required as otherwise B2 has the same hash as A2 and won't get imported
+	builder.push_transfer(Transfer {
+		from: Keyring::Alice.to_raw_public().into(),
+		to: Keyring::Ferdie.to_raw_public().into(),
+		amount: 41,
+		nonce: 0,
+	}).unwrap();
+	let b2 = builder.bake().unwrap();
+	client.import(BlockOrigin::Own, b2.clone()).unwrap();
+
+	// B2 -> B3
+	let b3 = client.new_block_at(&BlockId::Hash(b2.hash())).unwrap().bake().unwrap();
+	client.import(BlockOrigin::Own, b3.clone()).unwrap();
+
+	// B3 -> B4
+	let b4 = client.new_block_at(&BlockId::Hash(b3.hash())).unwrap().bake().unwrap();
+	client.import(BlockOrigin::Own, b4.clone()).unwrap();
+
+	// // B2 -> C3
+	let mut builder = client.new_block_at(&BlockId::Hash(b2.hash())).unwrap();
+	// this push is required as otherwise C3 has the same hash as B3 and won't get imported
+	builder.push_transfer(Transfer {
+		from: Keyring::Alice.to_raw_public().into(),
+		to: Keyring::Ferdie.to_raw_public().into(),
+		amount: 1,
+		nonce: 1,
+	}).unwrap();
+	let c3 = builder.bake().unwrap();
+	client.import(BlockOrigin::Own, c3.clone()).unwrap();
+
+	// A1 -> D2
+	let mut builder = client.new_block_at(&BlockId::Hash(a1.hash())).unwrap();
+	// this push is required as otherwise D2 has the same hash as B2 and won't get imported
+	builder.push_transfer(Transfer {
+		from: Keyring::Alice.to_raw_public().into(),
+		to: Keyring::Ferdie.to_raw_public().into(),
+		amount: 1,
+		nonce: 0,
+	}).unwrap();
+	let d2 = builder.bake().unwrap();
+	client.import(BlockOrigin::Own, d2.clone()).unwrap();
+
+	let genesis_hash = client.info().unwrap().chain.genesis_hash;
+
+	let children1 = backend.blockchain().children(a4.hash()).unwrap();
+	assert_eq!(vec![a5.hash()], children1);
+
+	let children2 = backend.blockchain().children(a1.hash()).unwrap();
+	assert_eq!(vec![a2.hash(), b2.hash(), d2.hash()], children2);
+
+	let children3 = backend.blockchain().children(genesis_hash).unwrap();
+	assert_eq!(vec![a1.hash()], children3);
+
+	let children4 = backend.blockchain().children(b2.hash()).unwrap();
+	assert_eq!(vec![b3.hash(), c3.hash()], children4);
+}
 
 pub fn test_blockchain_query_by_number_gets_canonical<B: 'static>(backend: Arc<B>) where
 	B: backend::LocalBackend<runtime::Block, Blake2Hasher>,