rapids_cpm_find is more invariant as one would expect

Fixes rapidsai#49

rapids_cpm_find now looks at the `GLOBAL_TARGETS` entries and
will not call CPMFindPackage if any of them already exist.

This makes it safe to call `rapids_cpm_find` no matter what
existing targets already exist. therefore users of rapids-cmake
don't need to do manual `if(TARGET ...)` checks, resulting
in missing packages in the export set.

rapids-cmake/cpm/find.cmake

@@ -44,16 +44,6 @@ consistency. List all targets used by your project in `GLOBAL_TARGET`.
 .. note::
   Requires :cmake:command:`rapids_cpm_init` to be called before usage
 
-.. note::
-  Adding an export set to :cmake:command:`rapids_cpm_find` has different behavior
-  for build and install. Build exports a respective CPM call, since
-  we presume other CPM packages don't generate a correct build directory
-  config module. While install exports a `find_dependency` call as
-  we expect projects to have a valid install setup.
-
-  If you need different behavior you will need to use :cmake:command:`rapids_export_package()`
-  or :cmake:command:`rapids_export_cpm()`.
-
 ``PackageName``
   Name of the package to find.
 
@@ -64,6 +54,13 @@ consistency. List all targets used by your project in `GLOBAL_TARGET`.
   Which targets from this package should be made global. This information
   will be propagated to any associated export set.
 
+  .. versionchanged:: v21.10.00
+    If any targets listed in `GLOBAL_TARGET` exist when :cmake:command:`rapids_cpm_find` is called
+    no calls to `CPM` will be executed. This is done for the following reasons:
+
+      - Removes the need for the calling code to do the conditional checks
+      - Allows `BUILD_EXPORT_SET` and `INSTALL_EXPORT_SET` tracking to happen correctly when targets had already been brought it by non-CPM means.
+
 ``BUILD_EXPORT_SET``
   Record that a :cmake:command:`CPMFindPackage(<PackageName> ...)` call needs to occur as part of
   our build directory export set.
@@ -77,6 +74,16 @@ consistency. List all targets used by your project in `GLOBAL_TARGET`.
   be passed down to :cmake:command:`CPMFindPackage`.
 
 
+.. note::
+  Adding an export set to :cmake:command:`rapids_cpm_find` has different behavior
+  for build and install. Build exports a respective CPM call, since
+  we presume other CPM packages don't generate a correct build directory
+  config module. While install exports a `find_dependency` call as
+  we expect projects to have a valid install setup.
+
+  If you need different behavior you will need to use :cmake:command:`rapids_export_package()`
+  or :cmake:command:`rapids_export_cpm()`.
+
 #]=======================================================================]
 function(rapids_cpm_find name version)
   list(APPEND CMAKE_MESSAGE_CONTEXT "rapids.cpm.find")
@@ -89,14 +96,25 @@ function(rapids_cpm_find name version)
     message(FATAL_ERROR "rapids_cpm_find requires you to specify CPM_ARGS before any CPM arguments")
   endif()
 
-  CPMFindPackage(NAME ${name} VERSION ${version} ${RAPIDS_UNPARSED_ARGUMENTS})
+  set(package_needs_to_be_added TRUE)
   if(RAPIDS_GLOBAL_TARGETS)
-    include("${rapids-cmake-dir}/cmake/make_global.cmake")
-    rapids_cmake_make_global(RAPIDS_GLOBAL_TARGETS)
+    foreach(target IN LISTS RAPIDS_GLOBAL_TARGETS)
+      if(TARGET ${target})
+        set(package_needs_to_be_added FALSE)
+        break()
+      endif()
+    endforeach()
+  endif()
+
+  if(package_needs_to_be_added)
+    CPMFindPackage(NAME ${name} VERSION ${version} ${RAPIDS_UNPARSED_ARGUMENTS})
   endif()
 
   set(extra_info)
   if(RAPIDS_GLOBAL_TARGETS)
+    include("${rapids-cmake-dir}/cmake/make_global.cmake")
+    rapids_cmake_make_global(RAPIDS_GLOBAL_TARGETS)
+
     set(extra_info "GLOBAL_TARGETS")
     list(APPEND extra_info ${RAPIDS_GLOBAL_TARGETS})
   endif()

testing/cpm/CMakeLists.txt

@@ -16,4 +16,6 @@
 add_cmake_config_test( rapids-cpm.cmake )
 
 add_cmake_config_test( cpm_find-existing-build-dir )
+add_cmake_config_test( cpm_find-existing-target )
+add_cmake_config_test( cpm_find-existing-target-to-export-sets )
 add_cmake_config_test( cpm_find-options-escaped )

testing/cpm/cpm_find-existing-target-to-export-sets/CMakeLists.txt

@@ -0,0 +1,82 @@
+#=============================================================================
+# Copyright (c) 2018-2021, NVIDIA CORPORATION.
+#
+# 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.
+#=============================================================================
+cmake_minimum_required(VERSION 3.20)
+
+include(${rapids-cmake-dir}/cpm/init.cmake)
+include(${rapids-cmake-dir}/cpm/find.cmake)
+include(${rapids-cmake-dir}/export/write_dependencies.cmake)
+
+project(rapids-existing-target LANGUAGES CXX)
+
+include("${rapids-cmake-testing-dir}/cpm/make_fake_project_build_dir_with_config.cmake")
+
+make_fake_project_build_dir_with_config(RapidsTestFind 2021.01.02
+    RapidsTestFindConfig.cmake
+    RapidsTestFindConfigVersion.cmake)
+
+rapids_cpm_init()
+
+set(CMAKE_PREFIX_PATH
+  "${CMAKE_CURRENT_BINARY_DIR}/RapidsTestFind-build/"
+  )
+
+
+add_library(RapidsTest::RapidsTest IMPORTED INTERFACE)
+
+rapids_cpm_find(RapidsTestFind 2021.01.02
+  GLOBAL_TARGETS RapidsTest::RapidsTest
+  INSTALL_EXPORT_SET setA)
+
+rapids_cpm_find(RapidsTestFind 2021.01.02
+  GLOBAL_TARGETS RapidsTest::RapidsTest
+  INSTALL_EXPORT_SET setB)
+
+rapids_cpm_find(RapidsTestFind 2021.01.02
+  GLOBAL_TARGETS RapidsTest::RapidsTest
+  BUILD_EXPORT_SET setB)
+
+
+function(verify_dependency_file file_name to_match)
+  file(STRINGS "${file_name}" text)
+  set(package_dependency_found FALSE)
+
+  foreach(line IN LISTS text)
+    if( line MATCHES ${to_match})
+      set(package_dependency_found TRUE)
+      break()
+    endif()
+  endforeach()
+
+  if(NOT package_dependency_found)
+    message(FATAL_ERROR "${file_name} failed to export RapidsTestFind properly")
+  endif()
+
+endfunction()
+
+set(file_path "${CMAKE_CURRENT_BINARY_DIR}/build_export_set.cmake")
+file(REMOVE "${file_path}")
+rapids_export_write_dependencies(build setB "${file_path}")
+verify_dependency_file("${file_path}" "[=[NAME;RapidsTestFind;VERSION;2021.01.02]=]")
+
+set(file_path "${CMAKE_CURRENT_BINARY_DIR}/install_export_setA.cmake")
+file(REMOVE "${CMAKE_CURRENT_BINARY_DIR}/install_export_setA.cmake")
+rapids_export_write_dependencies(build setB "${file_path}")
+verify_dependency_file("${file_path}" "[=[find_dependency(RapidsTestFind)]=]")
+
+set(file_path "${CMAKE_CURRENT_BINARY_DIR}/install_export_setB.cmake")
+file(REMOVE "${CMAKE_CURRENT_BINARY_DIR}/install_export_setB.cmake")
+rapids_export_write_dependencies(build setB "${file_path}")
+verify_dependency_file("${file_path}" "[=[find_dependency(RapidsTestFind)]=]")

testing/cpm/cpm_find-existing-target-to-export-sets/RapidsTestFindConfig.cmake

@@ -0,0 +1,22 @@
+#=============================================================================
+# Copyright (c) 2018-2021, NVIDIA CORPORATION.
+#
+# 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.
+#=============================================================================
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/RapidsTestFindConfigVersion.cmake")
+
+add_library(RapidsTest::RapidsTest IMPORTED INTERFACE GLOBAL)
+
+check_required_components(RapidsTest2)

testing/cpm/cpm_find-existing-target/CMakeLists.txt

@@ -0,0 +1,37 @@
+#=============================================================================
+# Copyright (c) 2018-2021, NVIDIA CORPORATION.
+#
+# 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(${rapids-cmake-dir}/cpm/init.cmake)
+include(${rapids-cmake-dir}/cpm/find.cmake)
+
+cmake_minimum_required(VERSION 3.20)
+project(rapids-existing-target LANGUAGES CXX)
+
+include("${rapids-cmake-testing-dir}/cpm/make_fake_project_build_dir_with_config.cmake")
+
+make_fake_project_build_dir_with_config(RapidsTestFind 2021.01.02
+    RapidsTestFindConfig.cmake
+    RapidsTestFindConfigVersion.cmake)
+
+rapids_cpm_init()
+
+set(CMAKE_PREFIX_PATH
+  "${CMAKE_CURRENT_BINARY_DIR}/RapidsTestFind-build/"
+  )
+
+
+add_library(RapidsTest::RapidsTest IMPORTED INTERFACE)
+
+rapids_cpm_find(RapidsTestFind 2021.01.02 GLOBAL_TARGETS RapidsTest::RapidsTest)

testing/cpm/cpm_find-existing-target/RapidsTestFindConfig.cmake

@@ -0,0 +1,22 @@
+#=============================================================================
+# Copyright (c) 2018-2021, NVIDIA CORPORATION.
+#
+# 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.
+#=============================================================================
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/RapidsTestFindConfigVersion.cmake")
+
+add_library(RapidsTest::RapidsTest IMPORTED INTERFACE GLOBAL)
+
+check_required_components(RapidsTest2)

testing/export/write_dependencies-duplicate-packages.cmake

@@ -29,7 +29,6 @@ rapids_export_write_dependencies(build test_set "${CMAKE_CURRENT_BINARY_DIR}/exp
 
 file(STRINGS "${CMAKE_CURRENT_BINARY_DIR}/export_set.cmake" text)
 
-set(duplicate_package )
 foreach(line IN LISTS text)
   # message(STATUS "1. line: ${line}")
   if( line MATCHES "find_dependency\\(ExactlyDuplicate\\)" )