CMake: Fixes for generated config (#1212)

* CMake: Add option to set the package install dir.

* CMake: Fix generated config.

- `YAML_CPP_SHARED_LIBS_BUILT` should not be set with a `PATH_VAR` as it
would always evaluate to true.
- `YAML_CPP_LIBRARIES` should used the exported target name including
the namespace, but `check_required_components` shouldn't.
- Use `CMAKE_CURRENT_LIST_DIR` to find the target file, instead of a
`PATH_VAR`. Package managers such as vcpkg move CMake configs after
installing.

* CI: Test the generated CMake package.

* CMake: Create add a deprecated yaml-cpp target.

This target is meant to provide compatibility with versions prior to
0.8.0.

* CMake: mark the yaml-cpp target as IMPORTED.

---------

Co-authored-by: Jesse Beder <jbeder+github@gmail.com>

.github/workflows/build.yml

@@ -6,6 +6,9 @@ on:
     branches: [ master ]
   workflow_dispatch:
 permissions: read-all
+defaults:
+  run:
+    shell: bash
 jobs:
   cmake-build:
       strategy:
@@ -26,23 +29,59 @@ jobs:
         YAML_BUILD_SHARED_LIBS: ${{ matrix.build == 'shared' && 'ON' || 'OFF' }}
         CMAKE_GENERATOR: >-
           ${{format(matrix.generator != 'Default Generator' && '-G "{0}"' || '', matrix.generator)}}
+        CMAKE_INSTALL_PREFIX: "${{ github.workspace }}/install-prefix"
+        CMAKE_BUILD_TYPE: Debug
       runs-on: ${{ matrix.os }}
       steps:
-        - uses: actions/checkout@v2
+        - uses: actions/checkout@v3
 
-        - name: Get number of CPU cores
-          uses: SimenB/github-actions-cpu-cores@v1
-
-        - name: Build Tests
-          shell: bash
+        - name: Configure
           run: |
-            cmake ${{ env.CMAKE_GENERATOR }} -S "${{ github.workspace }}" -B build -DCMAKE_CXX_STANDARD=${{ matrix.cxx_standard }} -DYAML_BUILD_SHARED_LIBS=${{ env.YAML_BUILD_SHARED_LIBS }} -DYAML_CPP_BUILD_TESTS=ON
-            cd build && cmake --build . --parallel ${{ steps.cpu-cores.outputs.count }}
+            cmake \
+              ${{ env.CMAKE_GENERATOR }} \
+              -S "${{ github.workspace }}" \
+              -B build \
+              -D CMAKE_CXX_STANDARD=${{ matrix.cxx_standard }} \
+              -D CMAKE_INSTALL_PREFIX="${{ env.CMAKE_INSTALL_PREFIX }}" \
+              -D CMAKE_BUILD_TYPE=${{ env.CMAKE_BUILD_TYPE }} \
+              -D YAML_BUILD_SHARED_LIBS=${{ env.YAML_BUILD_SHARED_LIBS }} \
+              -D YAML_CPP_BUILD_TESTS=ON
+
+        - name: Build
+          run: |
+            cmake \
+              --build build \
+              --config ${{ env.CMAKE_BUILD_TYPE }} \
+              --verbose \
+              --parallel
 
         - name: Run Tests
           shell: bash
           run: |
-            cd build && ctest -C Debug --output-on-failure --verbose
+            ctest \
+              --test-dir build \
+              --build-config ${{ env.CMAKE_BUILD_TYPE }} \
+              --output-on-failure \
+              --verbose
+
+        - name: Install
+          run: cmake --install build --config ${{ env.CMAKE_BUILD_TYPE }}
+
+        - name: Configure CMake package test
+          run: |
+            cmake \
+              ${{ env.CMAKE_GENERATOR }} \
+              -S "${{ github.workspace }}/test/cmake" \
+              -B consumer-build \
+              -D CMAKE_BUILD_TYPE=${{ env.CMAKE_BUILD_TYPE }} \
+              -D CMAKE_PREFIX_PATH="${{ env.CMAKE_INSTALL_PREFIX }}"
+
+        - name: Build CMake package test
+          run: |
+            cmake \
+              --build consumer-build \
+              --config ${{ env.CMAKE_BUILD_TYPE }} \
+              --verbose
 
   bazel-build:
       strategy:
@@ -50,16 +89,14 @@ jobs:
           os: [ubuntu-latest, windows-latest, macos-latest]
       runs-on: ${{ matrix.os }}
       steps:
-        - uses: actions/checkout@v2
+        - uses: actions/checkout@v3
 
         - name: Build
-          shell: bash
           run: |
             cd "${{ github.workspace }}"
             bazel build :all
 
         - name: Test
-          shell: bash
           run: |
             cd "${{ github.workspace }}"
             bazel test test

CMakeLists.txt

@@ -34,6 +34,8 @@ cmake_dependent_option(YAML_CPP_BUILD_TESTS
 cmake_dependent_option(YAML_MSVC_SHARED_RT
   "MSVC: Build yaml-cpp with shared runtime libs (/MD)" ON
   "CMAKE_SYSTEM_NAME MATCHES Windows" OFF)
+set(YAML_CPP_INSTALL_CMAKEDIR "${CMAKE_INSTALL_LIBDIR}/cmake/yaml-cpp"
+  CACHE STRING "Path to install the CMake package to")
  
 if (YAML_CPP_FORMAT_SOURCE)
     find_program(YAML_CPP_CLANG_FORMAT_EXE NAMES clang-format)
@@ -146,13 +148,12 @@ set_target_properties(yaml-cpp PROPERTIES
   PROJECT_LABEL "yaml-cpp ${yaml-cpp-label-postfix}"
   DEBUG_POSTFIX "${CMAKE_DEBUG_POSTFIX}")
 
-set(CONFIG_EXPORT_DIR "${CMAKE_INSTALL_LIBDIR}/cmake/yaml-cpp")
-set(EXPORT_TARGETS yaml-cpp)
+set(EXPORT_TARGETS yaml-cpp::yaml-cpp)
 configure_package_config_file(
   "${PROJECT_SOURCE_DIR}/yaml-cpp-config.cmake.in"
   "${PROJECT_BINARY_DIR}/yaml-cpp-config.cmake"
-  INSTALL_DESTINATION "${CONFIG_EXPORT_DIR}"
-  PATH_VARS CMAKE_INSTALL_INCLUDEDIR CMAKE_INSTALL_LIBDIR CONFIG_EXPORT_DIR YAML_BUILD_SHARED_LIBS)
+  INSTALL_DESTINATION "${YAML_CPP_INSTALL_CMAKEDIR}"
+  PATH_VARS CMAKE_INSTALL_INCLUDEDIR CMAKE_INSTALL_LIBDIR)
 unset(EXPORT_TARGETS)
 
 write_basic_package_version_file(
@@ -172,15 +173,14 @@ if (YAML_CPP_INSTALL)
                 FILES_MATCHING PATTERN "*.h")
   install(EXPORT yaml-cpp-targets
     NAMESPACE yaml-cpp::
-    DESTINATION "${CONFIG_EXPORT_DIR}")
+    DESTINATION "${YAML_CPP_INSTALL_CMAKEDIR}")
   install(FILES
       "${PROJECT_BINARY_DIR}/yaml-cpp-config.cmake"
       "${PROJECT_BINARY_DIR}/yaml-cpp-config-version.cmake"
-    DESTINATION "${CONFIG_EXPORT_DIR}")
+    DESTINATION "${YAML_CPP_INSTALL_CMAKEDIR}")
   install(FILES "${PROJECT_BINARY_DIR}/yaml-cpp.pc"
     DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 endif()
-unset(CONFIG_EXPORT_DIR)
 
 if(YAML_CPP_BUILD_TESTS)
   add_subdirectory(test)

test/cmake/CMakeLists.txt

@@ -0,0 +1,19 @@
+cmake_minimum_required(VERSION 3.5)
+project(yaml-cpp-consumer LANGUAGES CXX)
+
+find_package(yaml-cpp CONFIG REQUIRED)
+get_target_property(LIBRARY_TYPE yaml-cpp::yaml-cpp TYPE)
+
+if(LIBRARY_TYPE STREQUAL "SHARED_LIBRARY")
+  if(NOT YAML_CPP_SHARED_LIBS_BUILT)
+    message(FATAL_ERROR "Library type (${LIBRARY_TYPE}) contradicts config: ${YAML_CPP_SHARED_LIBS_BUILT}")
+  endif()
+else()
+  if(YAML_CPP_SHARED_LIBS_BUILT)
+    message(FATAL_ERROR "Library type (${LIBRARY_TYPE}) contradicts config: ${YAML_CPP_SHARED_LIBS_BUILT}")
+  endif()
+endif()
+
+add_executable(main main.cpp)
+set_target_properties(main PROPERTIES CXX_STANDARD 11)
+target_link_libraries(main PRIVATE ${YAML_CPP_LIBRARIES})

test/cmake/main.cpp

@@ -0,0 +1,3 @@
+#include "yaml-cpp/yaml.h"
+
+int main(int, char**) { YAML::Parser foo{}; }

yaml-cpp-config.cmake.in

@@ -11,12 +11,20 @@ set_and_check(YAML_CPP_INCLUDE_DIR "@PACKAGE_CMAKE_INSTALL_INCLUDEDIR@")
 set_and_check(YAML_CPP_LIBRARY_DIR "@PACKAGE_CMAKE_INSTALL_LIBDIR@")
 
 # Are we building shared libraries?
-set(YAML_CPP_SHARED_LIBS_BUILT "@PACKAGE_YAML_BUILD_SHARED_LIBS@")
+set(YAML_CPP_SHARED_LIBS_BUILT @YAML_BUILD_SHARED_LIBS@)
 
 # Our library dependencies (contains definitions for IMPORTED targets)
-include(@PACKAGE_CONFIG_EXPORT_DIR@/yaml-cpp-targets.cmake)
+include("${CMAKE_CURRENT_LIST_DIR}/yaml-cpp-targets.cmake")
 
 # These are IMPORTED targets created by yaml-cpp-targets.cmake
 set(YAML_CPP_LIBRARIES "@EXPORT_TARGETS@")
 
-check_required_components(@EXPORT_TARGETS@)
+add_library(yaml-cpp INTERFACE IMPORTED)
+target_link_libraries(yaml-cpp INTERFACE yaml-cpp::yaml-cpp)
+if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.17)
+  set_target_properties(yaml-cpp PROPERTIES 
+    DEPRECATION "The target yaml-cpp is deprecated and will be removed in version 0.10.0. Use the yaml-cpp::yaml-cpp target instead."
+  )
+endif()
+
+check_required_components(yaml-cpp)