doxygen get_target_property with non-existent target

[v4hn]

Hey,

I just tried to compile a hydro-workspace with cmake 3.0 and get the following warning
for a number of packages:

==> Processing catkin package: 'gencpp'
==> Building with env: '/home/v4hn/ros/hydro/core/env.sh'
Makefile exists, skipping explicit cmake invocation...
==> make cmake_check_build_system in '/home/v4hn/ros/hydro/core-build/build_isolated/gencpp'
-- Using CATKIN_DEVEL_PREFIX: /home/v4hn/ros/hydro/core-build/devel_isolated/gencpp
-- Using CMAKE_PREFIX_PATH: /home/v4hn/ros/hydro/core
-- This workspace overlays: /home/v4hn/ros/hydro/core
-- Using PYTHON_EXECUTABLE: /usr/bin/python
-- Python version: 2.7
-- Using default Python package layout
-- Using CATKIN_ENABLE_TESTING: ON
-- Call enable_testing()
-- Using CATKIN_TEST_RESULTS_DIR: /home/v4hn/ros/hydro/core-build/build_isolated/gencpp/test_results
-- Found gtest: gtests will be built
CMake Warning (dev) at /home/v4hn/ros/hydro/core/share/catkin/cmake/tools/doxygen.cmake:40 (GET_TARGET_PROPERTY):
  Policy CMP0045 is not set: Error on non-existent target in
  get_target_property.  Run "cmake --help-policy CMP0045" for policy details.
  Use the cmake_policy command to set the policy and suppress this warning.

  get_target_property() called with non-existent target "doxygen".
Call Stack (most recent call first):
  /home/v4hn/ros/hydro/core/share/catkin/cmake/all.cmake:139 (include)
  /home/v4hn/ros/hydro/core/share/catkin/cmake/catkinConfig.cmake:20 (include)
  CMakeLists.txt:3 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

This goes back to a change by @vrabaud in 2012: b1ba803
To be honest I can't really see the point of this whole block...

[vrabaud]

I guess this block:

GET_TARGET_PROPERTY(doxygen_catkin_property doxygen "catkin")
if (doxygen_catkin_property)
    else()

should be replaced by:

if (NOT TARGET doxygen)

Can you please see if it works for you ? Thx

[dirk-thomas]

I assume the target property and the comment are also not needed. Please see #661 for a proposed fix.

[v4hn]

Thank you for resolving this so quickly!