fix(cmake): install DeePMD config for C library builds (#5475)

Problem
- Installing DeePMD-kit against a precompiled `libdeepmd_c` skipped
CMake package config generation.
- LAMMPS built-in mode then failed at `find_package(DeePMD)` because no
`DeePMDConfig.cmake`/`DeePMDTargets.cmake` was installed.

Change
- Generate `DeePMDConfig.cmake` for `DEEPMD_C_ROOT` builds.
- Install an imported `DeePMD::deepmd_c` target pointing at the imported
C library.
- Include equivalent package metadata in the packaged `libdeepmd_c`
tarball.

Verification
- `git diff --check`
- Configured a fake precompiled C-library prefix and verified
`find_package(DeePMD REQUIRED CONFIG)` exposes `DeePMD::deepmd_c` with
the expected imported library/include paths.

Fixes #5035

Authored by OpenClaw (model: custom-chat-jinzhezeng-group/gpt-5.5)


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
* Improved C API packaging and CMake config for more reliable discovery
and linking.
* Standardized install layout under lib/cmake/<project> and added
packaged/imported targets for consistent consumption.
* Enhanced package/version file generation to support builds that
include only the C interface.
* **Tests**
* Added a consumer build step to validate the installed package and
linking experience.

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Author: njzjz-bot

source/CMakeLists.txt

@@ -1,6 +1,7 @@
 # new in 3.25: RUN_OUTPUT_STDOUT_VARIABLE
 cmake_minimum_required(VERSION 3.25.2)
 project(DeePMD)
+include(CMakePackageConfigHelpers)
 
 option(ENABLE_TENSORFLOW "Enable TensorFlow interface" OFF)
 option(ENABLE_PYTORCH "Enable PyTorch interface" OFF)
@@ -584,34 +585,35 @@ add_custom_target(lammps COMMAND ${CMAKE_COMMAND} -P
                                  ${CMAKE_CURRENT_BINARY_DIR}/cmake_lammps.cmake)
 
 # add configure file
-if(BUILD_CPP_IF
-   AND NOT BUILD_PY_IF
-   AND NOT DEEPMD_C_ROOT)
-  include(CMakePackageConfigHelpers)
+if(BUILD_CPP_IF AND NOT BUILD_PY_IF)
   set(targets_export_name
       ${CMAKE_PROJECT_NAME}Targets
       CACHE INTERNAL "")
   set(generated_dir
       "${CMAKE_CURRENT_BINARY_DIR}/generated"
       CACHE INTERNAL "")
-  set(cmake_files_install_dir
-      "${CMAKE_INSTALL_PREFIX}/lib/cmake/${CMAKE_PROJECT_NAME}")
+  set(cmake_files_install_dir "lib/cmake/${CMAKE_PROJECT_NAME}")
   set(version_file "${generated_dir}/${CMAKE_PROJECT_NAME}ConfigVersion.cmake")
   write_basic_package_version_file(
     ${version_file}
     VERSION $<IF:${GIT_SUMM}?${GIT_SUMM}:0.0.0>
     COMPATIBILITY AnyNewerVersion)
-  install(
-    EXPORT ${targets_export_name}
-    NAMESPACE ${CMAKE_PROJECT_NAME}::
-    DESTINATION ${cmake_files_install_dir})
   set(config_file "${generated_dir}/${CMAKE_PROJECT_NAME}Config.cmake")
   configure_package_config_file(
     "${CMAKE_CURRENT_SOURCE_DIR}/cmake/Config.cmake.in" "${config_file}"
     INSTALL_DESTINATION ${cmake_files_install_dir})
   install(FILES ${version_file} ${config_file}
           DESTINATION ${cmake_files_install_dir})
-endif(
-  BUILD_CPP_IF
-  AND NOT BUILD_PY_IF
-  AND NOT DEEPMD_C_ROOT)
+  if(DEEPMD_C_ROOT)
+    configure_file(
+      "${CMAKE_CURRENT_SOURCE_DIR}/cmake/DeePMDImportedTargets.cmake.in"
+      "${generated_dir}/${targets_export_name}.cmake" @ONLY)
+    install(FILES "${generated_dir}/${targets_export_name}.cmake"
+            DESTINATION ${cmake_files_install_dir})
+  else()
+    install(
+      EXPORT ${targets_export_name}
+      NAMESPACE ${CMAKE_PROJECT_NAME}::
+      DESTINATION ${cmake_files_install_dir})
+  endif()
+endif()

source/api_c/CMakeLists.txt

@@ -59,6 +59,27 @@ if(PACKAGE_C)
   install(TARGETS ${libname} DESTINATION ${CMAKE_BINARY_DIR}/libdeepmd_c/lib)
   install(TARGETS ${LIB_DEEPMD_OP}
           DESTINATION ${CMAKE_BINARY_DIR}/libdeepmd_c/lib)
+
+  set(cmake_files_install_dir
+      "${CMAKE_BINARY_DIR}/libdeepmd_c/lib/cmake/${CMAKE_PROJECT_NAME}")
+  set(targets_export_name ${CMAKE_PROJECT_NAME}Targets)
+  set(generated_dir "${CMAKE_CURRENT_BINARY_DIR}/generated")
+  set(version_file "${generated_dir}/${CMAKE_PROJECT_NAME}ConfigVersion.cmake")
+  write_basic_package_version_file(
+    ${version_file}
+    VERSION $<IF:${GIT_SUMM}?${GIT_SUMM}:0.0.0>
+    COMPATIBILITY AnyNewerVersion)
+  set(config_file "${generated_dir}/${CMAKE_PROJECT_NAME}Config.cmake")
+  configure_package_config_file(
+    "${CMAKE_CURRENT_SOURCE_DIR}/../cmake/Config.cmake.in" "${config_file}"
+    INSTALL_DESTINATION "lib/cmake/${CMAKE_PROJECT_NAME}")
+  install(FILES ${version_file} ${config_file}
+          DESTINATION "${cmake_files_install_dir}")
+  configure_file(
+    "${CMAKE_CURRENT_SOURCE_DIR}/../cmake/DeePMDPackagedTargets.cmake.in"
+    "${generated_dir}/${targets_export_name}.cmake" @ONLY)
+  install(FILES "${generated_dir}/${targets_export_name}.cmake"
+          DESTINATION "${cmake_files_install_dir}")
 endif()
 
 if(CMAKE_TESTING_ENABLED)

source/cmake/Config.cmake.in

@@ -2,4 +2,4 @@
 include(CMakeFindDependencyMacro)
 
 include("${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake")
-check_required_components("@project_name@")
+check_required_components("@CMAKE_PROJECT_NAME@")

source/cmake/DeePMDImportedTargets.cmake.in

@@ -0,0 +1,7 @@
+if(NOT TARGET @CMAKE_PROJECT_NAME@::@LIB_DEEPMD_C@)
+  add_library(@CMAKE_PROJECT_NAME@::@LIB_DEEPMD_C@ SHARED IMPORTED)
+  set_target_properties(
+    @CMAKE_PROJECT_NAME@::@LIB_DEEPMD_C@
+    PROPERTIES IMPORTED_LOCATION "@deepmd_c@" INTERFACE_INCLUDE_DIRECTORIES
+                                              "@DEEPMD_INCLUDE_C_DIR@")
+endif()

source/cmake/DeePMDPackagedTargets.cmake.in

@@ -0,0 +1,9 @@
+if(NOT TARGET @CMAKE_PROJECT_NAME@::@LIB_DEEPMD_C@)
+  add_library(@CMAKE_PROJECT_NAME@::@LIB_DEEPMD_C@ SHARED IMPORTED)
+  set_target_properties(
+    @CMAKE_PROJECT_NAME@::@LIB_DEEPMD_C@
+    PROPERTIES
+      IMPORTED_LOCATION
+      "${PACKAGE_PREFIX_DIR}/lib/@CMAKE_SHARED_LIBRARY_PREFIX@@LIB_DEEPMD_C@@CMAKE_SHARED_LIBRARY_SUFFIX@"
+      INTERFACE_INCLUDE_DIRECTORIES "${PACKAGE_PREFIX_DIR}/include")
+endif()

source/install/build_from_c.sh

@@ -1,21 +1,44 @@
 set -e
 
-SCRIPT_PATH=$(dirname $(realpath -s $0))
-if [ -z "$INSTALL_PREFIX" ]; then
-	INSTALL_PREFIX=$(realpath -s ${SCRIPT_PATH}/../../dp)
+SCRIPT_PATH=$(dirname "$(realpath -s "$0")")
+if [ -z "${INSTALL_PREFIX}" ]; then
+	INSTALL_PREFIX=$(realpath -s "${SCRIPT_PATH}/../../dp")
 fi
-mkdir -p ${INSTALL_PREFIX}
+mkdir -p "${INSTALL_PREFIX}"
 echo "Installing DeePMD-kit to ${INSTALL_PREFIX}"
 NPROC=$(nproc --all)
 
 #------------------
 
-BUILD_TMP_DIR=${SCRIPT_PATH}/../build
-mkdir -p ${BUILD_TMP_DIR}
-cd ${BUILD_TMP_DIR}
-cmake -DCMAKE_INSTALL_PREFIX=${INSTALL_PREFIX} -DDEEPMD_C_ROOT=${DEEPMD_C_ROOT} -DLAMMPS_VERSION=stable_22Jul2025_update2 ..
-cmake --build . -j${NPROC}
+BUILD_TMP_DIR="${SCRIPT_PATH}/../build"
+mkdir -p "${BUILD_TMP_DIR}"
+cd "${BUILD_TMP_DIR}"
+cmake -DCMAKE_INSTALL_PREFIX="${INSTALL_PREFIX}" -DDEEPMD_C_ROOT="${DEEPMD_C_ROOT}" -DLAMMPS_VERSION=stable_22Jul2025_update2 ..
+cmake --build . -j"${NPROC}"
 cmake --install .
+
+CONSUMER_TMP_DIR="${BUILD_TMP_DIR}/cmake-consumer"
+rm -rf "${CONSUMER_TMP_DIR}"
+mkdir -p "${CONSUMER_TMP_DIR}"
+cat >"${CONSUMER_TMP_DIR}/CMakeLists.txt" <<'EOF'
+cmake_minimum_required(VERSION 3.25)
+project(deepmd_c_consumer LANGUAGES CXX)
+find_package(DeePMD REQUIRED CONFIG)
+find_package(DeePMD REQUIRED CONFIG)
+if(NOT TARGET DeePMD::deepmd_c)
+  message(FATAL_ERROR "DeePMD::deepmd_c target is missing")
+endif()
+add_executable(deepmd_c_consumer main.cc)
+target_link_libraries(deepmd_c_consumer PRIVATE DeePMD::deepmd_c)
+EOF
+cat >"${CONSUMER_TMP_DIR}/main.cc" <<'EOF'
+#include <deepmd/c_api.h>
+
+int main() { return 0; }
+EOF
+cmake -S "${CONSUMER_TMP_DIR}" -B "${CONSUMER_TMP_DIR}/build" -DCMAKE_PREFIX_PATH="${INSTALL_PREFIX}"
+cmake --build "${CONSUMER_TMP_DIR}/build" -j"${NPROC}"
+
 cmake --build . --target=lammps
 
 #------------------