Fix get_json_object dropping object fields that follow an empty key

cpp/src/json/json_path.cu

@@ -355,7 +355,8 @@ class json_state : private parser {
    * The user can specify whether or not the name string must be present via
    * the `can_be_empty` flag.
    *
-   * When a name is present, it must be followed by a colon `:`
+   * When a name is present, it must be followed by a colon `:`. A present but zero-length
+   * name (the `""` key of `{"":1}`) is not an absent name.
    *
    * @param[out] name The resulting name.
    * @param can_be_empty Parameter indicating whether it is valid for the name
@@ -366,17 +367,16 @@ class json_state : private parser {
   {
     char const quote = options.get_allow_single_quotes() ? 0 : '\"';
 
-    if (parse_string(name, can_be_empty, quote) == parse_result::ERROR) {
-      return parse_result::ERROR;
+    if (auto const result = parse_string(name, can_be_empty, quote);
+        result != parse_result::SUCCESS) {
+      return result;
     }
 
-    // if we got a real string, the next char must be a :
-    if (name.size_bytes() > 0) {
-      if (!parse_whitespace()) { return parse_result::ERROR; }
-      if (*pos == ':') {
-        pos++;
-        return parse_result::SUCCESS;
-      }
+    // a name is present, so the next char must be a :
+    if (!parse_whitespace()) { return parse_result::ERROR; }
+    if (*pos == ':') {
+      pos++;
+      return parse_result::SUCCESS;
     }
     return parse_result::EMPTY;
   }

cpp/tests/json/json_tests.cpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2021-2026, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2021-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -1044,6 +1044,21 @@ TEST_F(JsonPathTests, QueriesContainingQuotes)
   do_test(R"($.'A)", R"({"B'": 3})");
 }
 
+TEST_F(JsonPathTests, ObjectWithEmptyKey)
+{
+  auto const input = cudf::test::strings_column_wrapper{R"({"":0,"a":1})",
+                                                        R"({"a":1,"":0})",
+                                                        R"({"" : 0, "a" : 1})",
+                                                        R"({"":{"a":9},"a":1})",
+                                                        R"({"":[1,2],"a":1})",
+                                                        R"({"":"s","a":1})"};
+
+  auto const result =
+    cudf::get_json_object(cudf::strings_column_view(input), std::string_view{"$.a"});
+  auto const expected = cudf::test::strings_column_wrapper{"1", "1", "1", "1", "1", "1"};
+  CUDF_TEST_EXPECT_COLUMNS_EQUIVALENT(*result, expected);
+}
+
 // Test that get_json_object creates valid string columns for empty/whitespace JSONPath queries
 TEST_F(JsonPathTests, EmptyPathCreatesValidColumn)
 {