example package that causes cmake errors when changing rosidl generation target name

CMakeLists.txt

cmake_minimum_required(VERSION 3.5)

project(test_pkg)

find_package(ament_cmake REQUIRED)
find_package(rosidl_default_generators REQUIRED)

rosidl_generate_interfaces(${PROJECT_NAME}_ext_to_avoid_target_collision "msg/MyMsg.msg")

ament_package()

MyMsg.msg

# Place this in the msg folder

int32 foo

package.xml

<?xml version="1.0"?>
<?xml-model
  href="http://download.ros.org/schema/package_format2.xsd"
  schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="3">
  <name>test_pkg</name>
  <version>0.0.1</version>
  <description>
    test_pkg
  </description>
  <maintainer email="nobody@example.com">Nobody</maintainer>
  <license>Apache License 2.0</license>

  <buildtool_depend>ament_cmake</buildtool_depend>

  <build_depend>rosidl_default_generators</build_depend>
  <exec_depend>rosidl_default_runtime</exec_depend>

  <member_of_group>rosidl_interface_packages</member_of_group>

  <export>
    <build_type>ament_cmake</build_type>
  </export>
</package>