cmExportFileGenerator: export private compile info for C++ modules

When consuming exported targets which contain C++ modules, the consuming
project must be able to recompile BMI files using the original target's
flags. This is because a module source may use some private target usage
requirement but not want to propagate it to consumers. To facilitate
this, export the private information as necessary for consumers to be
able to perform the BMI compilations.

13 files changed, 412 insertions, 0 deletions

diff --git a/Tests/RunCMake/CXXModules/RunCMakeTest.cmake b/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
index 25670bd..d2fb11f 100644
--- a/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
@@ -187,6 +187,7 @@ endif ()
 if ("export_bmi" IN_LIST CMake_TEST_MODULE_COMPILATION)
   run_cxx_module_test(export-interface-no-properties-build)
   run_cxx_module_test(export-interface-build)
+  run_cxx_module_test(export-usage-build)
   run_cxx_module_test(export-bmi-and-interface-build)
 endif ()
 
@@ -201,6 +202,7 @@ if ("install_bmi" IN_LIST CMake_TEST_MODULE_COMPILATION)
   if ("export_bmi" IN_LIST CMake_TEST_MODULE_COMPILATION)
     run_cxx_module_test(export-interface-no-properties-install)
     run_cxx_module_test(export-interface-install)
+    run_cxx_module_test(export-usage-install)
     run_cxx_module_test(export-bmi-and-interface-install)
   endif ()
 endif ()
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-build-stderr.txt b/Tests/RunCMake/CXXModules/examples/export-usage-build-stderr.txt
new file mode 100644
index 0000000..78bdf2b
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-build-stderr.txt
@@ -0,0 +1,4 @@
+CMake Warning \(dev\) at CMakeLists.txt:7 \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-build/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-usage-build/CMakeLists.txt
new file mode 100644
index 0000000..86a608b
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-build/CMakeLists.txt
@@ -0,0 +1,110 @@
+cmake_minimum_required(VERSION 3.24)
+project(cxx_modules_export_usage CXX)
+
+include("${CMAKE_SOURCE_DIR}/../cxx-modules-rules.cmake")
+
+add_library(export_usage STATIC)
+target_sources(export_usage
+  PRIVATE
+    forward.cxx
+  PRIVATE
+    FILE_SET modules_private TYPE CXX_MODULES
+      BASE_DIRS
+        "${CMAKE_CURRENT_SOURCE_DIR}"
+      FILES
+        private.cxx
+  PUBLIC
+    FILE_SET modules TYPE CXX_MODULES
+      BASE_DIRS
+        "${CMAKE_CURRENT_SOURCE_DIR}"
+      FILES
+        importable.cxx)
+target_compile_features(export_usage PUBLIC cxx_std_20)
+
+list(APPEND CMAKE_CXX_KNOWN_FEATURES
+  exported
+  buildiface
+  installiface
+  buildlocaliface)
+
+target_include_directories(export_usage
+  PRIVATE
+    "/usr/exported"
+    "$<BUILD_INTERFACE:/usr/buildiface>"
+    "$<INSTALL_INTERFACE:/usr/installiface>"
+    "$<BUILD_LOCAL_INTERFACE:/usr/buildlocaliface>")
+target_compile_definitions(export_usage
+  PRIVATE
+    "exported"
+    "$<BUILD_INTERFACE:buildiface>"
+    "$<INSTALL_INTERFACE:installiface>"
+    "$<BUILD_LOCAL_INTERFACE:buildlocaliface>")
+target_compile_features(export_usage
+  PRIVATE
+    "cxx_std_11"
+    "$<BUILD_INTERFACE:cxx_std_14>"
+    "$<INSTALL_INTERFACE:cxx_std_17>"
+    "$<BUILD_LOCAL_INTERFACE:cxx_std_20>")
+
+if (MSVC)
+  set(variable_flag "-constexpr:depth")
+else ()
+  set(variable_flag "-fconstexpr-depth=")
+endif ()
+
+target_compile_options(export_usage
+  PRIVATE
+    "${variable_flag}100"
+    "$<BUILD_INTERFACE:${variable_flag}200>"
+    "$<INSTALL_INTERFACE:${variable_flag}300>"
+    "$<BUILD_LOCAL_INTERFACE:${variable_flag}400>")
+
+add_library(export_used INTERFACE)
+add_library(export_build INTERFACE)
+add_library(export_install INTERFACE)
+add_library(export_never INTERFACE)
+
+target_link_libraries(export_usage
+  PRIVATE
+    "export_used"
+    "$<BUILD_INTERFACE:export_build>"
+    "$<INSTALL_INTERFACE:export_install>"
+    "$<BUILD_LOCAL_INTERFACE:export_never>")
+
+install(TARGETS export_usage
+  EXPORT CXXModules
+  FILE_SET modules DESTINATION "lib/cxx/miu")
+export(EXPORT CXXModules
+  NAMESPACE CXXModules::
+  FILE "${CMAKE_CURRENT_BINARY_DIR}/export_usage-targets.cmake")
+install(TARGETS export_used export_build export_install
+  EXPORT CXXModulesDeps)
+export(EXPORT CXXModulesDeps
+  NAMESPACE CXXModules::
+  FILE "${CMAKE_CURRENT_BINARY_DIR}/export_usage-dep-targets.cmake")
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/export_usage-config.cmake"
+  "include(\"\${CMAKE_CURRENT_LIST_DIR}/export_usage-dep-targets.cmake\")
+include(\"\${CMAKE_CURRENT_LIST_DIR}/export_usage-targets.cmake\")
+set(\${CMAKE_FIND_PACKAGE_NAME}_FOUND 1)
+")
+
+set(generator
+  -G "${CMAKE_GENERATOR}")
+if (CMAKE_GENERATOR_TOOLSET)
+  list(APPEND generator
+    -T "${CMAKE_GENERATOR_TOOLSET}")
+endif ()
+if (CMAKE_GENERATOR_PLATFORM)
+  list(APPEND generator
+    -A "${CMAKE_GENERATOR_PLATFORM}")
+endif ()
+
+add_test(NAME export_usage_build
+  COMMAND
+    "${CMAKE_COMMAND}"
+    "-Dexpected_dir=${CMAKE_CURRENT_SOURCE_DIR}"
+    "-Dexport_interfaces_flag=${variable_flag}"
+    "-Dexport_usage_DIR=${CMAKE_CURRENT_BINARY_DIR}"
+    ${generator}
+    -S "${CMAKE_CURRENT_SOURCE_DIR}/test"
+    -B "${CMAKE_CURRENT_BINARY_DIR}/test")
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-build/forward.cxx b/Tests/RunCMake/CXXModules/examples/export-usage-build/forward.cxx
new file mode 100644
index 0000000..7f53271
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-build/forward.cxx
@@ -0,0 +1,6 @@
+import priv;
+
+int forwarding()
+{
+  return from_private();
+}
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-build/importable.cxx b/Tests/RunCMake/CXXModules/examples/export-usage-build/importable.cxx
new file mode 100644
index 0000000..e0b1872
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-build/importable.cxx
@@ -0,0 +1,8 @@
+export module importable;
+
+int forwarding();
+
+export int from_import()
+{
+  return forwarding();
+}
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-build/private.cxx b/Tests/RunCMake/CXXModules/examples/export-usage-build/private.cxx
new file mode 100644
index 0000000..c5b719a
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-build/private.cxx
@@ -0,0 +1,6 @@
+export module priv;
+
+export int from_private()
+{
+  return 0;
+}
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-build/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-usage-build/test/CMakeLists.txt
new file mode 100644
index 0000000..88bda88
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-build/test/CMakeLists.txt
@@ -0,0 +1,69 @@
+cmake_minimum_required(VERSION 3.24)
+project(cxx_modules_library NONE)
+
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+
+find_package(export_usage REQUIRED)
+
+if (NOT TARGET CXXModules::export_usage)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (NOT TARGET CXXModules::export_used)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (NOT TARGET CXXModules::export_build)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (NOT TARGET CXXModules::export_install)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (TARGET CXXModules::export_never)
+  message(FATAL_ERROR
+    "Extra imported target")
+endif ()
+
+function (check_property expected property)
+  get_property(actual TARGET CXXModules::export_usage
+    PROPERTY "${property}")
+  if (NOT actual STREQUAL expected)
+    message(SEND_ERROR
+      "Mismatch for ${property}:\n  expected: ${expected}\n  actual: ${actual}")
+  endif ()
+endfunction ()
+
+check_property("/usr/exported;/usr/buildiface" "IMPORTED_CXX_MODULES_INCLUDE_DIRECTORIES")
+check_property("exported;buildiface" "IMPORTED_CXX_MODULES_COMPILE_DEFINITIONS")
+check_property("cxx_std_20;cxx_std_11;cxx_std_14" "IMPORTED_CXX_MODULES_COMPILE_FEATURES")
+check_property("${export_interfaces_flag}100;${export_interfaces_flag}200" "IMPORTED_CXX_MODULES_COMPILE_OPTIONS")
+check_property("$<COMPILE_ONLY:CXXModules::export_used>;$<COMPILE_ONLY:CXXModules::export_build>" "IMPORTED_CXX_MODULES_LINK_LIBRARIES")
+
+# Extract the export-dependent targets from the export file.
+file(STRINGS "${export_usage_DIR}/export_usage-targets.cmake" usage_dependent_targets
+  REGEX "foreach._target ")
+# Rudimentary argument splitting.
+string(REPLACE " " ";" usage_dependent_targets "${usage_dependent_targets}")
+# Keep only "target" names.
+list(FILTER usage_dependent_targets INCLUDE REGEX "CXXModules::")
+# Strip quotes.
+string(REPLACE "\"" "" usage_dependent_targets "${usage_dependent_targets}")
+
+if (NOT "CXXModules::export_used" IN_LIST usage_dependent_targets)
+  message(SEND_ERROR
+    "The main export does not require the 'CXXModules::export_used' target")
+endif ()
+if (NOT "CXXModules::export_build" IN_LIST usage_dependent_targets)
+  message(SEND_ERROR
+    "The main export does not require the 'CXXModules::export_build' target")
+endif ()
+if ("CXXModules::export_install" IN_LIST usage_dependent_targets)
+  message(SEND_ERROR
+    "The main export requires the 'CXXModules::export_install' target")
+endif ()
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-install-stderr.txt b/Tests/RunCMake/CXXModules/examples/export-usage-install-stderr.txt
new file mode 100644
index 0000000..78bdf2b
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-install-stderr.txt
@@ -0,0 +1,4 @@
+CMake Warning \(dev\) at CMakeLists.txt:7 \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-install/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-usage-install/CMakeLists.txt
new file mode 100644
index 0000000..11f53b0
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-install/CMakeLists.txt
@@ -0,0 +1,114 @@
+cmake_minimum_required(VERSION 3.24)
+project(cxx_modules_export_usage CXX)
+
+include("${CMAKE_SOURCE_DIR}/../cxx-modules-rules.cmake")
+
+add_library(export_usage STATIC)
+target_sources(export_usage
+  PRIVATE
+    forward.cxx
+  PRIVATE
+    FILE_SET modules_private TYPE CXX_MODULES
+      BASE_DIRS
+        "${CMAKE_CURRENT_SOURCE_DIR}"
+      FILES
+        private.cxx
+  PUBLIC
+    FILE_SET modules TYPE CXX_MODULES
+      BASE_DIRS
+        "${CMAKE_CURRENT_SOURCE_DIR}"
+      FILES
+        importable.cxx)
+target_compile_features(export_usage PUBLIC cxx_std_20)
+
+list(APPEND CMAKE_CXX_KNOWN_FEATURES
+  exported
+  buildiface
+  installiface
+  buildlocaliface)
+
+target_include_directories(export_usage
+  PRIVATE
+    "/usr/exported"
+    "$<BUILD_INTERFACE:/usr/buildiface>"
+    "$<INSTALL_INTERFACE:/usr/installiface>"
+    "$<BUILD_LOCAL_INTERFACE:/usr/buildlocaliface>")
+target_compile_definitions(export_usage
+  PRIVATE
+    "exported"
+    "$<BUILD_INTERFACE:buildiface>"
+    "$<INSTALL_INTERFACE:installiface>"
+    "$<BUILD_LOCAL_INTERFACE:buildlocaliface>")
+target_compile_features(export_usage
+  PRIVATE
+    "cxx_std_11"
+    "$<BUILD_INTERFACE:cxx_std_14>"
+    "$<INSTALL_INTERFACE:cxx_std_17>"
+    "$<BUILD_LOCAL_INTERFACE:cxx_std_20>")
+
+if (MSVC)
+  set(variable_flag "-constexpr:depth")
+else ()
+  set(variable_flag "-fconstexpr-depth=")
+endif ()
+
+target_compile_options(export_usage
+  PRIVATE
+    "${variable_flag}100"
+    "$<BUILD_INTERFACE:${variable_flag}200>"
+    "$<INSTALL_INTERFACE:${variable_flag}300>"
+    "$<BUILD_LOCAL_INTERFACE:${variable_flag}400>")
+
+add_library(export_used INTERFACE)
+add_library(export_build INTERFACE)
+add_library(export_install INTERFACE)
+add_library(export_never INTERFACE)
+
+target_link_libraries(export_usage
+  PRIVATE
+    "export_used"
+    "$<BUILD_INTERFACE:export_build>"
+    "$<INSTALL_INTERFACE:export_install>"
+    "$<BUILD_LOCAL_INTERFACE:export_never>")
+
+install(TARGETS export_usage
+  EXPORT CXXModules
+  FILE_SET modules DESTINATION "lib/cxx/miu")
+install(EXPORT CXXModules
+  NAMESPACE CXXModules::
+  DESTINATION "lib/cmake/export_usage"
+  FILE "export_usage-targets.cmake")
+install(TARGETS export_used export_build export_install
+  EXPORT CXXModulesDeps)
+install(EXPORT CXXModulesDeps
+  NAMESPACE CXXModules::
+  DESTINATION "lib/cmake/export_usage"
+  FILE "export_usage-dep-targets.cmake")
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/export_usage-config.cmake"
+  "include(\"\${CMAKE_CURRENT_LIST_DIR}/export_usage-dep-targets.cmake\")
+include(\"\${CMAKE_CURRENT_LIST_DIR}/export_usage-targets.cmake\")
+set(\${CMAKE_FIND_PACKAGE_NAME}_FOUND 1)
+")
+install(FILES "${CMAKE_CURRENT_BINARY_DIR}/export_usage-config.cmake"
+  DESTINATION "lib/cmake/export_usage")
+
+set(generator
+  -G "${CMAKE_GENERATOR}")
+if (CMAKE_GENERATOR_TOOLSET)
+  list(APPEND generator
+    -T "${CMAKE_GENERATOR_TOOLSET}")
+endif ()
+if (CMAKE_GENERATOR_PLATFORM)
+  list(APPEND generator
+    -A "${CMAKE_GENERATOR_PLATFORM}")
+endif ()
+
+add_test(NAME export_usage_build
+  COMMAND
+    "${CMAKE_COMMAND}"
+    "-Dexpected_dir=${CMAKE_INSTALL_PREFIX}/lib/cxx/miu"
+    "-Dexport_interfaces_flag=${variable_flag}"
+    "-Dexport_usage_DIR=${CMAKE_INSTALL_PREFIX}/lib/cmake/export_usage"
+    ${generator}
+    -S "${CMAKE_CURRENT_SOURCE_DIR}/test"
+    -B "${CMAKE_CURRENT_BINARY_DIR}/test")
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-install/forward.cxx b/Tests/RunCMake/CXXModules/examples/export-usage-install/forward.cxx
new file mode 100644
index 0000000..7f53271
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-install/forward.cxx
@@ -0,0 +1,6 @@
+import priv;
+
+int forwarding()
+{
+  return from_private();
+}
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-install/importable.cxx b/Tests/RunCMake/CXXModules/examples/export-usage-install/importable.cxx
new file mode 100644
index 0000000..e0b1872
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-install/importable.cxx
@@ -0,0 +1,8 @@
+export module importable;
+
+int forwarding();
+
+export int from_import()
+{
+  return forwarding();
+}
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-install/private.cxx b/Tests/RunCMake/CXXModules/examples/export-usage-install/private.cxx
new file mode 100644
index 0000000..c5b719a
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-install/private.cxx
@@ -0,0 +1,6 @@
+export module priv;
+
+export int from_private()
+{
+  return 0;
+}
diff --git a/Tests/RunCMake/CXXModules/examples/export-usage-install/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-usage-install/test/CMakeLists.txt
new file mode 100644
index 0000000..bdc2898
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-install/test/CMakeLists.txt
@@ -0,0 +1,69 @@
+cmake_minimum_required(VERSION 3.24)
+project(cxx_modules_library NONE)
+
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+
+find_package(export_usage REQUIRED)
+
+if (NOT TARGET CXXModules::export_usage)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (NOT TARGET CXXModules::export_used)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (NOT TARGET CXXModules::export_build)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (NOT TARGET CXXModules::export_install)
+  message(FATAL_ERROR
+    "Missing imported target")
+endif ()
+
+if (TARGET CXXModules::export_never)
+  message(FATAL_ERROR
+    "Extra imported target")
+endif ()
+
+function (check_property expected property)
+  get_property(actual TARGET CXXModules::export_usage
+    PROPERTY "${property}")
+  if (NOT actual STREQUAL expected)
+    message(SEND_ERROR
+      "Mismatch for ${property}:\n  expected: ${expected}\n  actual  : ${actual}")
+  endif ()
+endfunction ()
+
+check_property("/usr/exported;/usr/installiface" "IMPORTED_CXX_MODULES_INCLUDE_DIRECTORIES")
+check_property("exported;installiface" "IMPORTED_CXX_MODULES_COMPILE_DEFINITIONS")
+check_property("cxx_std_20;cxx_std_11;cxx_std_17" "IMPORTED_CXX_MODULES_COMPILE_FEATURES")
+check_property("${export_interfaces_flag}100;${export_interfaces_flag}300" "IMPORTED_CXX_MODULES_COMPILE_OPTIONS")
+check_property("$<COMPILE_ONLY:CXXModules::export_used>;$<COMPILE_ONLY:CXXModules::export_install>" "IMPORTED_CXX_MODULES_LINK_LIBRARIES")
+
+# Extract the export-dependent targets from the export file.
+file(STRINGS "${export_usage_DIR}/export_usage-targets.cmake" usage_dependent_targets
+  REGEX "foreach._target ")
+# Rudimentary argument splitting.
+string(REPLACE " " ";" usage_dependent_targets "${usage_dependent_targets}")
+# Keep only "target" names.
+list(FILTER usage_dependent_targets INCLUDE REGEX "CXXModules::")
+# Strip quotes.
+string(REPLACE "\"" "" usage_dependent_targets "${usage_dependent_targets}")
+
+if (NOT "CXXModules::export_used" IN_LIST usage_dependent_targets)
+  message(SEND_ERROR
+    "The main export does not require the 'CXXModules::export_used' target")
+endif ()
+if ("CXXModules::export_build" IN_LIST usage_dependent_targets)
+  message(SEND_ERROR
+    "The main export requires the 'CXXModules::export_build' target")
+endif ()
+if (NOT "CXXModules::export_install" IN_LIST usage_dependent_targets)
+  message(SEND_ERROR
+    "The main export does not require the 'CXXModules::export_install' target")
+endif ()