Fix issue centrifuge#66 by returning a bool if a storage value is empty

rpc/state/get_child_storage.go

@@ -21,23 +21,30 @@ import (
 	"github.com/centrifuge/go-substrate-rpc-client/types"
 )
 
-// GetChildStorage retreives the child storage for a key and decodes them into the provided interface
-func (s *State) GetChildStorage(childStorageKey, key types.StorageKey, target interface{}, blockHash types.Hash) error {
+// GetChildStorage retreives the child storage for a key and decodes them into the provided interface. Ok is true if the
+// value is not empty.
+func (s *State) GetChildStorage(childStorageKey, key types.StorageKey, target interface{}, blockHash types.Hash) (ok bool, err error) {
 	raw, err := s.getChildStorageRaw(childStorageKey, key, &blockHash)
 	if err != nil {
-		return err
+		return false, err
 	}
-	return types.DecodeFromBytes(*raw, target)
+	if len(*raw) == 0 {
+		return false, nil
+	}
+	return true, types.DecodeFromBytes(*raw, target)
 }
 
 // GetChildStorageLatest retreives the child storage for a key for the latest block height and decodes them into the
-// provided interface
-func (s *State) GetChildStorageLatest(childStorageKey, key types.StorageKey, target interface{}) error {
+// provided interface. Ok is true if the value is not empty.
+func (s *State) GetChildStorageLatest(childStorageKey, key types.StorageKey, target interface{}) (ok bool, err error) {
 	raw, err := s.getChildStorageRaw(childStorageKey, key, nil)
 	if err != nil {
-		return err
+		return false, err
+	}
+	if len(*raw) == 0 {
+		return false, nil
 	}
-	return types.DecodeFromBytes(*raw, target)
+	return true, types.DecodeFromBytes(*raw, target)
 }
 
 // GetChildStorageRaw retreives the child storage for a key as raw bytes, without decoding them

rpc/state/get_child_storage_test.go

@@ -28,14 +28,16 @@ var key = types.NewStorageKey(types.MustHexDecodeString(mockSrv.childStorageTrie
 
 func TestState_GetChildStorageLatest(t *testing.T) {
 	var decoded ChildStorageTrieTestVal
-	err := state.GetChildStorageLatest(childStorageKey, key, &decoded)
+	ok, err := state.GetChildStorageLatest(childStorageKey, key, &decoded)
+	assert.True(t, ok)
 	assert.NoError(t, err)
 	assert.Equal(t, mockSrv.childStorageTrieValue, decoded)
 }
 
 func TestState_GetChildStorage(t *testing.T) {
 	var decoded ChildStorageTrieTestVal
-	err := state.GetChildStorageLatest(childStorageKey, key, &decoded)
+	ok, err := state.GetChildStorageLatest(childStorageKey, key, &decoded)
+	assert.True(t, ok)
 	assert.NoError(t, err)
 	assert.Equal(t, mockSrv.childStorageTrieValue, decoded, mockSrv.blockHashLatest)
 }

rpc/state/get_storage.go

@@ -17,26 +17,37 @@
 package state
 
 import (
+	"fmt"
+
 	"github.com/centrifuge/go-substrate-rpc-client/client"
 	"github.com/centrifuge/go-substrate-rpc-client/types"
 )
 
-// GetStorage retreives the stored data and decodes them into the provided interface
-func (s *State) GetStorage(key types.StorageKey, target interface{}, blockHash types.Hash) error {
+// GetStorage retreives the stored data and decodes them into the provided interface. Ok is true if the value is not
+// empty.
+func (s *State) GetStorage(key types.StorageKey, target interface{}, blockHash types.Hash) (ok bool, err error) {
 	raw, err := s.getStorageRaw(key, &blockHash)
 	if err != nil {
-		return err
+		return false, err
+	}
+	fmt.Printf("%#v", raw)
+	if len(*raw) == 0 {
+		return false, nil
 	}
-	return types.DecodeFromBytes(*raw, target)
+	return true, types.DecodeFromBytes(*raw, target)
 }
 
-// GetStorageLatest retreives the stored data for the latest block height and decodes them into the provided interface
-func (s *State) GetStorageLatest(key types.StorageKey, target interface{}) error {
+// GetStorageLatest retreives the stored data for the latest block height and decodes them into the provided interface.
+// Ok is true if the value is not empty.
+func (s *State) GetStorageLatest(key types.StorageKey, target interface{}) (ok bool, err error) {
 	raw, err := s.getStorageRaw(key, nil)
 	if err != nil {
-		return err
+		return false, err
+	}
+	if len(*raw) == 0 {
+		return false, nil
 	}
-	return types.DecodeFromBytes(*raw, target)
+	return true, types.DecodeFromBytes(*raw, target)
 }
 
 // GetStorageRaw retreives the stored data as raw bytes, without decoding them

rpc/state/get_storage_test.go

@@ -25,18 +25,27 @@ import (
 
 func TestState_GetStorageLatest(t *testing.T) {
 	var decoded types.U64
-	err := state.GetStorageLatest(types.MustHexDecodeString(mockSrv.storageKeyHex), &decoded)
+	ok, err := state.GetStorageLatest(types.MustHexDecodeString(mockSrv.storageKeyHex), &decoded)
 	assert.NoError(t, err)
+	assert.True(t, ok)
 	assert.Equal(t, types.U64(0x5d892db8), decoded)
 }
 
 func TestState_GetStorage(t *testing.T) {
 	var decoded types.U64
-	err := state.GetStorage(types.MustHexDecodeString(mockSrv.storageKeyHex), &decoded, mockSrv.blockHashLatest)
+	ok, err := state.GetStorage(types.MustHexDecodeString(mockSrv.storageKeyHex), &decoded, mockSrv.blockHashLatest)
 	assert.NoError(t, err)
+	assert.True(t, ok)
 	assert.Equal(t, types.U64(0x5d892db8), decoded)
 }
 
+func TestState_GetStorageEmpty(t *testing.T) {
+	var decoded types.U64
+	ok, err := state.GetStorage([]byte{0xab}, &decoded, mockSrv.blockHashLatest)
+	assert.NoError(t, err)
+	assert.False(t, ok)
+}
+
 func TestState_GetStorageRawLatest(t *testing.T) {
 	data, err := state.GetStorageRawLatest(types.MustHexDecodeString(mockSrv.storageKeyHex))
 	assert.NoError(t, err)

rpc/state/state_test.go

@@ -53,6 +53,7 @@ type MockSrv struct {
 	metadata                 *types.Metadata
 	runtimeVersion           types.RuntimeVersion
 	storageKeyHex            string
+	storageKeyHexEmpty       string
 	storageChangeSets        []types.StorageChangeSet
 	storageDataHex           string
 	storageSize              types.U64
@@ -82,7 +83,7 @@ func (s *MockSrv) GetKeys(key string, hash *string) []string {
 
 func (s *MockSrv) GetStorage(key string, hash *string) string {
 	if key != s.storageKeyHex {
-		panic("key not found")
+		return ""
 	}
 	return mockSrv.storageDataHex
 }
@@ -168,6 +169,7 @@ var mockSrv = MockSrv{
 	metadataString:           types.ExamplaryMetadataV4String,
 	runtimeVersion:           types.RuntimeVersion{APIs: []types.RuntimeVersionAPI{{APIID: "0xdf6acb689907609b", Version: 0x2}, {APIID: "0x37e397fc7c91f5e4", Version: 0x1}, {APIID: "0x40fe3ad401f8959a", Version: 0x3}, {APIID: "0xd2bc9897eed08f15", Version: 0x1}, {APIID: "0xf78b278be53f454c", Version: 0x1}, {APIID: "0xed99c5acb25eedf5", Version: 0x2}, {APIID: "0xdd718d5cc53262d4", Version: 0x1}, {APIID: "0x7801759919ee83e5", Version: 0x1}}, AuthoringVersion: 0xa, ImplName: "substrate-node", ImplVersion: 0x3e, SpecName: "node", SpecVersion: 0x3c}, //nolint:lll
 	storageKeyHex:            "0x0e4944cfd98d6f4cc374d16f5a4e3f9c",
+	storageKeyHexEmpty:       "0xeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
 	storageChangeSets:        []types.StorageChangeSet{{Block: types.Hash{0xdd, 0x18, 0x16, 0xb6, 0xf6, 0x88, 0x9f, 0x46, 0xe2, 0x3b, 0xd, 0x67, 0x50, 0xbc, 0x44, 0x1a, 0xf9, 0xda, 0xd0, 0xfd, 0xa8, 0xba, 0xe9, 0x6, 0x77, 0xc1, 0x70, 0x8d, 0x1, 0x3, 0x5f, 0xbe}, Changes: []types.KeyValueOption{{StorageKey: types.StorageKey{0xe, 0x49, 0x44, 0xcf, 0xd9, 0x8d, 0x6f, 0x4c, 0xc3, 0x74, 0xd1, 0x6f, 0x5a, 0x4e, 0x3f, 0x9c}, HasStorageData: true, StorageData: types.StorageDataRaw{0x88, 0x2, 0x66, 0x9f, 0x6e, 0x1, 0x0, 0x0}}}}, {Block: types.Hash{0x82, 0x14, 0xa1, 0x80, 0x8b, 0xd6, 0xb0, 0x46, 0xc8, 0x77, 0xa6, 0x4f, 0xce, 0xad, 0xb4, 0xa2, 0xa7, 0x3a, 0x65, 0x76, 0x9f, 0x61, 0x4, 0xc0, 0x20, 0xd7, 0x59, 0xad, 0x8f, 0x61, 0xc0, 0xd8}, Changes: []types.KeyValueOption{{StorageKey: types.StorageKey{0xe, 0x49, 0x44, 0xcf, 0xd9, 0x8d, 0x6f, 0x4c, 0xc3, 0x74, 0xd1, 0x6f, 0x5a, 0x4e, 0x3f, 0x9c}, HasStorageData: true, StorageData: types.StorageDataRaw{0x40, 0xe, 0x66, 0x9f, 0x6e, 0x1, 0x0, 0x0}}}}}, //nolint:lll
 	storageDataHex:           "0xb82d895d00000000",
 	storageSize:              926778,