DiceDB#1193: Add type check for string compatibility in evalAPPEND fu…

…nction (DiceDB#1237)

integration_tests/commands/http/append_test.go

@@ -90,6 +90,17 @@ func TestAPPEND(t *testing.T) {
 				{Command: "del", Body: map[string]interface{}{"key": "key"}},
 			},
 		},
+		{
+			name: "APPEND to key created using ZADD",
+			commands: []HTTPCommand{
+				{Command: "ZADD", Body: map[string]interface{}{"key": "myzset", "values": []string{"1", "one"}}},
+				{Command: "APPEND", Body: map[string]interface{}{"key": "myzset", "value": "two"}},
+			},
+			expected: []interface{}{float64(1), "WRONGTYPE Operation against a key holding the wrong kind of value"},
+			cleanup: []HTTPCommand{
+				{Command: "del", Body: map[string]interface{}{"key": "myzset"}},
+			},
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {

integration_tests/commands/resp/append_test.go

@@ -59,6 +59,12 @@ func TestAPPEND(t *testing.T) {
 			expected: []interface{}{int64(1), "WRONGTYPE Operation against a key holding the wrong kind of value"},
 			cleanup:  []string{"del key"},
 		},
+		{
+			name:     "APPEND to key created using ZADD",
+			commands: []string{"ZADD key 1 one", "APPEND key two"},
+			expected: []interface{}{int64(1), "WRONGTYPE Operation against a key holding the wrong kind of value"},
+			cleanup:  []string{"del key"},
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {

integration_tests/commands/websocket/append_test.go

@@ -45,6 +45,12 @@ func TestAppend(t *testing.T) {
 			expected:   []interface{}{float64(4)},
 			cleanupKey: "key1",
 		},
+		{
+			name:       "APPEND to key created using ZADD",
+			commands:   []string{"ZADD key 1 one", "APPEND key two"},
+			expected:   []interface{}{float64(1), "WRONGTYPE Operation against a key holding the wrong kind of value"},
+			cleanupKey: "key",
+		},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {

internal/eval/store_eval.go

@@ -1110,6 +1110,12 @@ func evalAPPEND(args []string, store *dstore.Store) *EvalResponse {
 		}
 	}
 	// Key exists path
+	if _, ok := obj.Value.(*sortedset.Set); ok {
+		return &EvalResponse{
+			Result: nil,
+			Error: diceerrors.ErrWrongTypeOperation,
+		}
+	}
 	_, currentEnc := object.ExtractTypeEncoding(obj)
 
 	var currentValueStr string