CPMFindPackage() unable to import namespaced targets

[Jonas Hjulstad]

I fetch a package from Git:

CPMFindPackage(NAME Pixman
GITHUB_REPOSITORY jonasbhjulstad/pixman-CMake
GIT_TAG master
)

With the following exported PixmanConfig.cmake (found in Pixman_BINARY_DIR):

include(CMakeFindDependencyMacro)
include(${CMAKE_CURRENT_LIST_DIR}/PixmanTargets.cmake)
add_library(Pixman::Pixman STATIC IMPORTED)

And the following PixmanTargets.cmake (found in Pixman_BINARY_DIR):

# Generated by CMake

if("${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION}" LESS 2.8)
   message(FATAL_ERROR "CMake >= 2.8.0 required")
endif()
if(CMAKE_VERSION VERSION_LESS "2.8.3")
   message(FATAL_ERROR "CMake >= 2.8.3 required")
endif()
cmake_policy(PUSH)
cmake_policy(VERSION 2.8.3...3.23)
#----------------------------------------------------------------
# Generated CMake target import file.
#----------------------------------------------------------------

# Commands may need to know the format version.
set(CMAKE_IMPORT_FILE_VERSION 1)

# Protect against multiple inclusion, which would fail when already imported targets are added once more.
set(_cmake_targets_defined "")
set(_cmake_targets_not_defined "")
set(_cmake_expected_targets "")
foreach(_cmake_expected_target IN ITEMS Pixman::Pixman)
  list(APPEND _cmake_expected_targets "${_cmake_expected_target}")
  if(TARGET "${_cmake_expected_target}")
    list(APPEND _cmake_targets_defined "${_cmake_expected_target}")
  else()
    list(APPEND _cmake_targets_not_defined "${_cmake_expected_target}")
  endif()
endforeach()
unset(_cmake_expected_target)
if(_cmake_targets_defined STREQUAL _cmake_expected_targets)
  unset(_cmake_targets_defined)
  unset(_cmake_targets_not_defined)
  unset(_cmake_expected_targets)
  unset(CMAKE_IMPORT_FILE_VERSION)
  cmake_policy(POP)
  return()
endif()
if(NOT _cmake_targets_defined STREQUAL "")
  string(REPLACE ";" ", " _cmake_targets_defined_text "${_cmake_targets_defined}")
  string(REPLACE ";" ", " _cmake_targets_not_defined_text "${_cmake_targets_not_defined}")
  message(FATAL_ERROR "Some (but not all) targets in this export set were already defined.\nTargets Defined: ${_cmake_targets_defined_text}\nTargets not yet defined: ${_cmake_targets_not_defined_text}\n")
endif()
unset(_cmake_targets_defined)
unset(_cmake_targets_not_defined)
unset(_cmake_expected_targets)


# Create imported target Pixman::Pixman
add_library(Pixman::Pixman STATIC IMPORTED)

set_target_properties(Pixman::Pixman PROPERTIES
  INTERFACE_INCLUDE_DIRECTORIES "/home/man/cairo-cmake/build/_deps/pixman_repo-build/pixman;/home/man/cairo-cmake/build/_deps/pixman_repo-src/pixman"
)

# Import target "Pixman::Pixman" for configuration ""
set_property(TARGET Pixman::Pixman APPEND PROPERTY IMPORTED_CONFIGURATIONS NOCONFIG)
set_target_properties(Pixman::Pixman PROPERTIES
  IMPORTED_LINK_INTERFACE_LANGUAGES_NOCONFIG "C"
  IMPORTED_LOCATION_NOCONFIG "/home/man/cairo-cmake/build/_deps/pixman_repo-build/pixman/libPixman.a"
  )

# This file does not depend on other imported targets which have
# been exported from the same project but in a separate export set.

# Commands beyond this point should not need to know the version.
set(CMAKE_IMPORT_FILE_VERSION)
cmake_policy(POP)

When I try to `target_link_libraries( Pixman::Pixman) the target is not found:

CMake Error at src/CMakeLists.txt:648 (target_link_libraries):
  Target "<target>" links to:

    Pixman::Pixman

[Claus Klein]

IMHO: It seems that the PixmanConfig.cmake is wrong?

CMake Error at stagedir/lib/cmake/Pixman/PixmanConfig.cmake:4 (add_library):
  add_library cannot create imported target "Pixman::Pixman" because another
  target with the same name already exists.
Call Stack (most recent call first):
  cmake/CPM.cmake:243 (find_package)
  cmake/CPM.cmake:652 (cpm_find_package)
  CMakeLists.txt:48 (CPMAddPackage)

This is not a CPM.cmake problem!

[Claus Klein]

Also it is not usable with CPM.cmake:

bash-3.2$ git diff
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4392ff9..000254b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -45,6 +45,11 @@ include(cmake/options.cmake)
 # PackageProject.cmake will be used to make our target installable
 CPMAddPackage("gh:TheLartians/PackageProject.cmake@1.10.0")
 
+CPMAddPackage(NAME Pixman
+  GITHUB_REPOSITORY jonasbhjulstad/pixman-CMake
+  GIT_TAG master
+)
+
 # NOTE: The fmt library must be installed if not found! BUT either clang-tidy checks nor compiler
 # warnings are wanted!
 
@@ -103,7 +108,7 @@ target_compile_options(${PROJECT_NAME} PRIVATE "$<$<COMPILE_LANG_AND_ID:CXX,MSVC
 target_compile_features(${PROJECT_NAME} PUBLIC cxx_std_20) # mimimum requierd for package user
 
 # Link dependencies
-target_link_libraries(${PROJECT_NAME} PUBLIC fmt::fmt)
+target_link_libraries(${PROJECT_NAME} PUBLIC fmt::fmt Pixman::Pixman)
 
 # target_include_directories with the SYSTEM modifier will request the compiler to omit warnings
 # from the provided paths, if the compiler supports that
@@ -132,7 +137,7 @@ packageProject(
   INCLUDE_DESTINATION include/${PROJECT_NAME}
   VERSION_HEADER ${VERSION_HEADER_LOCATION} DISABLE_VERSION_SUFFIX YES
   COMPATIBILITY SameMajorVersion
-  DEPENDENCIES "fmt 9.1.0"
+  DEPENDENCIES "fmt 9.1.0; Pixman"
 )
 
 include(CPack)
bash-3.2$ 

-- Configuring done
CMake Error at CMakeLists.txt:111 (target_link_libraries):
  Target "greeter" links to:

    Pixman::Pixman

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.

-- Generating done
CMake Generate step failed.  Build files cannot be regenerated correctly.
make: *** [install] Error 1
bash-3.2$ 

[Jonas Hjulstad]

PixmanConfig.cmake is the issue, sorry for the inconvenience.