feat(rpc): Implement childstate_getChildStorage RPC call

dot/rpc/modules/api_mocks.go

@@ -12,6 +12,7 @@ import (
 func NewMockStorageAPI() *modulesmocks.MockStorageAPI {
 	m := new(modulesmocks.MockStorageAPI)
 	m.On("GetStorage", mock.AnythingOfType("*common.Hash"), mock.AnythingOfType("[]uint8")).Return(nil, nil)
+	m.On("GetStorageFromChild", mock.AnythingOfType("*common.Hash"), mock.AnythingOfType("[]uint8"), mock.AnythingOfType("[]uint8")).Return(nil, nil)
 	m.On("Entries", mock.AnythingOfType("*common.Hash")).Return(nil, nil)
 	m.On("GetStorageByBlockHash", mock.AnythingOfType("common.Hash"), mock.AnythingOfType("[]uint8")).Return(nil, nil)
 	m.On("RegisterStorageObserver", mock.Anything)

dot/rpc/modules/childstate.go

@@ -29,6 +29,13 @@ type GetKeysRequest struct {
 	Hash   *common.Hash
 }
 
+// ChildStateStorageRequest holds json fields
+type ChildStateStorageRequest struct {
+	ChildStorageKey []byte       `json:"childStorageKey"`
+	Key             []byte       `json:"key"`
+	Hash            *common.Hash `json:"block"`
+}
+
 // GetStorageHash the request to get the entry child storage hash
 type GetStorageHash struct {
 	KeyChild []byte
@@ -140,3 +147,34 @@ func (cs *ChildStateModule) GetStorageHash(_ *http.Request, req *GetStorageHash,
 
 	return nil
 }
+
+// GetStorage returns a child storage entry.
+func (cs *ChildStateModule) GetStorage(_ *http.Request, req *ChildStateStorageRequest, res *StateStorageResponse) error {
+	var (
+		item []byte
+		err  error
+		hash common.Hash
+	)
+
+	if req.Hash == nil {
+		hash = cs.blockAPI.BestBlockHash()
+	} else {
+		hash = *req.Hash
+	}
+
+	stateRoot, err := cs.storageAPI.GetStateRootFromBlock(&hash)
+	if err != nil {
+		return err
+	}
+
+	item, err = cs.storageAPI.GetStorageFromChild(stateRoot, req.ChildStorageKey, req.Key)
+	if err != nil {
+		return err
+	}
+
+	if len(item) > 0 {
+		*res = StateStorageResponse(common.BytesToHex(item))
+	}
+
+	return nil
+}

dot/rpc/modules/childstate_test.go

@@ -17,6 +17,7 @@
 package modules
 
 import (
+	"encoding/hex"
 	"fmt"
 	"math/big"
 	"testing"
@@ -194,6 +195,60 @@ func TestGetStorageHash(t *testing.T) {
 	}
 }
 
+func TestGetChildStorage(t *testing.T) {
+	mod, blockHash := setupChildStateStorage(t)
+	randomHash, err := common.HexToHash(RandomHash)
+	require.NoError(t, err)
+
+	testCases := []struct {
+		params   []string
+		expected []byte
+		errMsg   string
+	}{
+		{params: []string{":child_storage_key", ""}, expected: nil},
+		{params: []string{":child_storage_key", ":child_first"}, expected: []byte(":child_first_value")},
+		{params: []string{":child_storage_key", ":child_first", blockHash.String()}, expected: []byte(":child_first_value")},
+		{params: []string{":child_storage_key", ":child_first", randomHash.String()}, errMsg: "Key not found"},
+	}
+
+	for _, test := range testCases {
+		t.Run(fmt.Sprintf("%s", test.params), func(t *testing.T) {
+			var res StateStorageResponse
+			var req ChildStateStorageRequest
+
+			if test.params[0] != "" {
+				req.ChildStorageKey = []byte(test.params[0])
+			}
+
+			if test.params[1] != "" {
+				req.Key = []byte(test.params[1])
+			}
+
+			if len(test.params) > 2 && test.params[2] != "" {
+				req.Hash = &common.Hash{}
+				*req.Hash, err = common.HexToHash(test.params[2])
+				require.NoError(t, err)
+			}
+
+			err = mod.GetStorage(nil, &req, &res)
+			// Handle error cases.
+			if test.errMsg != "" {
+				require.Error(t, err)
+				require.Equal(t, err.Error(), test.errMsg)
+				return
+			}
+
+			// Verify expected values.
+			require.NoError(t, err)
+			if test.expected != nil {
+				// Convert human-readable result value to hex.
+				expectedVal := "0x" + hex.EncodeToString(test.expected)
+				require.Equal(t, StateStorageResponse(expectedVal), res)
+			}
+		})
+	}
+}
+
 func setupChildStateStorage(t *testing.T) (*ChildStateModule, common.Hash) {
 	t.Helper()
 

dot/rpc/modules/state.go

@@ -41,13 +41,6 @@ type StateCallRequest struct {
 	Block  *common.Hash `json:"block"`
 }
 
-// StateChildStorageRequest holds json fields
-type StateChildStorageRequest struct {
-	ChildStorageKey []byte       `json:"childStorageKey"`
-	Key             []byte       `json:"key"`
-	Block           *common.Hash `json:"block"`
-}
-
 // StateStorageKeyRequest holds json fields
 type StateStorageKeyRequest struct {
 	Prefix   string       `json:"prefix"`
@@ -227,30 +220,6 @@ func (sm *StateModule) Call(_ *http.Request, _ *StateCallRequest, _ *StateCallRe
 	return nil
 }
 
-// GetChildKeys isn't implemented properly yet.
-func (*StateModule) GetChildKeys(_ *http.Request, _ *StateChildStorageRequest, _ *StateKeysResponse) error {
-	// TODO implement change storage trie so that block hash parameter works (See issue #834)
-	return nil
-}
-
-// GetChildStorage isn't implemented properly yet.
-func (*StateModule) GetChildStorage(_ *http.Request, _ *StateChildStorageRequest, _ *StateStorageDataResponse) error {
-	// TODO implement change storage trie so that block hash parameter works (See issue #834)
-	return nil
-}
-
-// GetChildStorageHash isn't implemented properly yet.
-func (*StateModule) GetChildStorageHash(_ *http.Request, _ *StateChildStorageRequest, _ *StateChildStorageResponse) error {
-	// TODO implement change storage trie so that block hash parameter works (See issue #834)
-	return nil
-}
-
-// GetChildStorageSize isn't implemented properly yet.
-func (*StateModule) GetChildStorageSize(_ *http.Request, _ *StateChildStorageRequest, _ *StateChildStorageSizeResponse) error {
-	// TODO implement change storage trie so that block hash parameter works (See issue #834)
-	return nil
-}
-
 // GetKeysPaged Returns the keys with prefix with pagination support.
 func (sm *StateModule) GetKeysPaged(_ *http.Request, req *StateStorageKeyRequest, res *StateStorageKeysResponse) error {
 	if req.Prefix == "" {

dot/rpc/modules/state_test.go

@@ -533,6 +533,7 @@ func setupStateModule(t *testing.T) (*StateModule, *common.Hash, *common.Hash) {
 
 	ts.Set([]byte(`:key2`), []byte(`value2`))
 	ts.Set([]byte(`:key1`), []byte(`value1`))
+	ts.SetChildStorage([]byte(`:child1`), []byte(`:key1`), []byte(`:childValue1`))
 
 	sr1, err := ts.Root()
 	require.NoError(t, err)

tests/rpc/rpc_05-state_test.go

@@ -61,30 +61,6 @@ func TestStateRPCResponseValidation(t *testing.T) {
 			method:      "state_getKeysPaged",
 			skip:        true,
 		},
-		{
-			description: "Test state_getChildKeys",
-			method:      "state_getChildKeys",
-			params:      `["","","0x579deccea7183c2afedbdaea59ad23e970458186afc4d57d5577842d4a219925"]`,
-			expected:    modules.StateKeysResponse{},
-		},
-		{
-			description: "Test state_getChildStorage",
-			method:      "state_getChildStorage",
-			params:      `["","","0x579deccea7183c2afedbdaea59ad23e970458186afc4d57d5577842d4a219925"]`,
-			expected:    modules.StateStorageDataResponse(""),
-		},
-		{
-			description: "Test state_getChildStorageHash",
-			method:      "state_getChildStorageHash",
-			params:      `["","","0x579deccea7183c2afedbdaea59ad23e970458186afc4d57d5577842d4a219925"]`,
-			expected:    modules.StateChildStorageResponse(""),
-		},
-		{
-			description: "Test state_getChildStorageSize",
-			method:      "state_getChildStorageSize",
-			params:      `["","","0x579deccea7183c2afedbdaea59ad23e970458186afc4d57d5577842d4a219925"]`,
-			expected:    modules.StateChildStorageSizeResponse(0),
-		},
 		{
 			description: "Test state_queryStorage",
 			method:      "state_queryStorage",