Fix format_as wrapping strings in double quotes + add unit tests

rosidlcpp_generator_core/CMakeLists.txt

@@ -27,6 +27,14 @@ install(TARGETS ${PROJECT_NAME}
 
 install(DIRECTORY include/ DESTINATION include)
 
+if(BUILD_TESTING)
+  find_package(ament_cmake_gtest REQUIRED)
+
+  ament_add_gtest(rosidlcpp_generator_core_test test/unit/rosidlcpp_generator_core_test.cpp)
+  target_link_libraries(rosidlcpp_generator_core_test ${PROJECT_NAME})
+  target_include_directories(rosidlcpp_generator_core_test PUBLIC include)
+endif()
+
 ament_export_include_directories("include/${PROJECT_NAME}")
 ament_export_libraries(${PROJECT_NAME})
 

rosidlcpp_generator_core/src/rosidlcpp_generator_core/generator_utils.cpp

@@ -35,11 +35,13 @@
 namespace nlohmann {
 
 std::string format_as(const json& j) {
-  return j.dump();
+  // dump() would wrap strings in double quotes, which is never what the generators want when
+  // interpolating names and namespaces into generated code.
+  return j.is_string() ? j.get<std::string>() : j.dump();
 }
 
 std::string format_as(const detail::iter_impl<const json>& j) {
-  return j->dump();
+  return format_as(*j);
 }
 
 }  // namespace nlohmann

rosidlcpp_generator_core/test/unit/rosidlcpp_generator_core_test.cpp

@@ -0,0 +1,80 @@
+// Copyright 2025 Anthony Welte
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <gtest/gtest.h>
+
+#include <nlohmann/json.hpp>
+
+#include <rosidlcpp_generator_core/generator_utils.hpp>
+
+using nlohmann::json;
+
+// Tests for format_as(const json&)
+
+TEST(FormatAsJsonTest, StringValueIsNotQuoted) {
+  json j = "hello";
+  EXPECT_EQ(nlohmann::format_as(j), "hello");
+}
+
+TEST(FormatAsJsonTest, StringValueWithSpecialCharacters) {
+  json j = "msg/UUID";
+  EXPECT_EQ(nlohmann::format_as(j), "msg/UUID");
+}
+
+TEST(FormatAsJsonTest, IntegerValueIsDumped) {
+  json j = 42;
+  EXPECT_EQ(nlohmann::format_as(j), "42");
+}
+
+TEST(FormatAsJsonTest, BoolValueIsDumped) {
+  json j = true;
+  EXPECT_EQ(nlohmann::format_as(j), "true");
+}
+
+TEST(FormatAsJsonTest, NullValueIsDumped) {
+  json j = nullptr;
+  EXPECT_EQ(nlohmann::format_as(j), "null");
+}
+
+TEST(FormatAsJsonTest, ArrayValueIsDumped) {
+  json j = json::array({1, 2, 3});
+  EXPECT_EQ(nlohmann::format_as(j), "[1,2,3]");
+}
+
+TEST(FormatAsJsonTest, ObjectValueIsDumped) {
+  json j = {{"key", "value"}};
+  EXPECT_EQ(nlohmann::format_as(j), "{\"key\":\"value\"}");
+}
+
+// Tests for format_as(const detail::iter_impl<const json>&)
+
+TEST(FormatAsIteratorTest, StringValueIsNotQuoted) {
+  json obj = {{"name", "msg"}};
+  auto it = obj.cbegin();
+  EXPECT_EQ(nlohmann::format_as(it), "msg");
+}
+
+TEST(FormatAsIteratorTest, IntegerValueIsDumped) {
+  json obj = {{"count", 7}};
+  auto it = obj.cbegin();
+  EXPECT_EQ(nlohmann::format_as(it), "7");
+}
+
+TEST(FormatAsIteratorTest, ArrayElementStringNotQuoted) {
+  json arr = json::array({"foo", "bar"});
+  auto it = arr.cbegin();
+  EXPECT_EQ(nlohmann::format_as(it), "foo");
+  ++it;
+  EXPECT_EQ(nlohmann::format_as(it), "bar");
+}