core: adjust System.Blockchain.GetContract interop

Part of #1055.

It should put on stack an array instead of interop interface.

pkg/compiler/syscall.go

@@ -14,7 +14,7 @@ var syscalls = map[string]map[string]Syscall{
 	},
 	"blockchain": {
 		"GetBlock":                {"System.Blockchain.GetBlock", true},
-		"GetContract":             {"System.Blockchain.GetContract", false},
+		"GetContract":             {"System.Blockchain.GetContract", true},
 		"GetHeight":               {"System.Blockchain.GetHeight", false},
 		"GetTransaction":          {"System.Blockchain.GetTransaction", true},
 		"GetTransactionFromBlock": {"System.Blockchain.GetTransactionFromBlock", false},

pkg/core/interop_system.go

@@ -83,6 +83,20 @@ func bcGetBlock(ic *interop.Context, v *vm.VM) error {
 	return nil
 }
 
+// contractToStackItem converts state.Contract to stackitem.Item
+func contractToStackItem(cs *state.Contract) (stackitem.Item, error) {
+	manifest, err := cs.Manifest.MarshalJSON()
+	if err != nil {
+		return nil, err
+	}
+	return stackitem.NewArray([]stackitem.Item{
+		stackitem.NewByteArray(cs.Script),
+		stackitem.NewByteArray(manifest),
+		stackitem.NewBool(cs.HasStorage()),
+		stackitem.NewBool(cs.IsPayable()),
+	}), nil
+}
+
 // bcGetContract returns contract.
 func bcGetContract(ic *interop.Context, v *vm.VM) error {
 	hashbytes := v.Estack().Pop().Bytes()
@@ -92,9 +106,13 @@ func bcGetContract(ic *interop.Context, v *vm.VM) error {
 	}
 	cs, err := ic.DAO.GetContractState(hash)
 	if err != nil {
-		v.Estack().PushVal([]byte{})
+		v.Estack().PushVal(stackitem.Null{})
 	} else {
-		v.Estack().PushVal(stackitem.NewInterop(cs))
+		item, err := contractToStackItem(cs)
+		if err != nil {
+			return err
+		}
+		v.Estack().PushVal(item)
 	}
 	return nil
 }

pkg/core/interop_system_test.go

@@ -292,3 +292,31 @@ func TestRuntimeGetInvocationCounter(t *testing.T) {
 		require.EqualValues(t, 42, v.Estack().Pop().BigInt().Int64())
 	})
 }
+
+func TestBlockchainGetContractState(t *testing.T) {
+	v, cs, ic, bc := createVMAndContractState(t)
+	defer bc.Close()
+	require.NoError(t, ic.DAO.PutContractState(cs))
+
+	t.Run("positive", func(t *testing.T) {
+		v.Estack().PushVal(cs.ScriptHash().BytesBE())
+		require.NoError(t, bcGetContract(ic, v))
+
+		expectedManifest, err := cs.Manifest.MarshalJSON()
+		require.NoError(t, err)
+		actual := v.Estack().Pop().Array()
+		require.Equal(t, 4, len(actual))
+		require.Equal(t, cs.Script, actual[0].Value().([]byte))
+		require.Equal(t, expectedManifest, actual[1].Value().([]byte))
+		require.Equal(t, cs.HasStorage(), actual[2].Bool())
+		require.Equal(t, cs.IsPayable(), actual[3].Bool())
+	})
+
+	t.Run("uncknown contract state", func(t *testing.T) {
+		v.Estack().PushVal(util.Uint160{1, 2, 3}.BytesBE())
+		require.NoError(t, bcGetContract(ic, v))
+
+		actual := v.Estack().Pop().Item()
+		require.Equal(t, stackitem.Null{}, actual)
+	})
+}

pkg/interop/blockchain/blockchain.go

@@ -3,10 +3,6 @@ Package blockchain provides functions to access various blockchain data.
 */
 package blockchain
 
-import (
-	"github.com/nspcc-dev/neo-go/pkg/interop/contract"
-)
-
 // Transaction represents a NEO transaction. It's similar to Transaction class
 // in Neo .net framework.
 type Transaction struct {
@@ -57,6 +53,14 @@ type Block struct {
 	TransactionsLength int
 }
 
+// Contract represents a Neo contract and is used in interop functions.
+type Contract struct {
+	Script     []byte
+	Manifest   []byte
+	HasStorage bool
+	IsPayable  bool
+}
+
 // GetHeight returns current block height (index of the last accepted block).
 // Note that when transaction is being run as a part of new block this block is
 // considered as not yet accepted (persisted) and thus you'll get an index of
@@ -99,6 +103,6 @@ func GetTransactionHeight(hash []byte) int {
 // format represented as a slice of 20 bytes). Refer to the `contract` package
 // for details on how to use the returned structure. This function uses
 // `System.Blockchain.GetContract` syscall.
-func GetContract(scriptHash []byte) contract.Contract {
-	return contract.Contract{}
+func GetContract(scriptHash []byte) Contract {
+	return Contract{}
 }