Merge topic 'imported-cxxmodules'

48ee946fdc cmExperimental: recycle the C++ modules API UUID
1a1806a71b gitlab-ci: declare `bmionly` support for modules where possible
457a12f3f9 Tests/RunCMake/CXXModules: add tests which use modules from imported targets
9b9ec70b54 Ninja: generate scanning and build rules for C++20 module synthetic targets
80ef50a191 CXXModules: add a variable for BMI-only compilation
80d6544398 cxxmodules: generate synthetic targets as an initial pass
3dc6676ecc cmSyntheticTargetCache: add a struct for synthetic target caching
cb356b540c cmCxxModuleUsageEffects: add a class to capture module usage effects
...

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !8535

31 files changed, 524 insertions, 10 deletions

diff --git a/Tests/RunCMake/CXXModules/CMakeLists.txt b/Tests/RunCMake/CXXModules/CMakeLists.txt
index ecc66b6..e23023d 100644
--- a/Tests/RunCMake/CXXModules/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModules/CMakeLists.txt
@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.23)
 project(${RunCMake_TEST} NONE)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 include(${RunCMake_TEST}.cmake)
diff --git a/Tests/RunCMake/CXXModules/RunCMakeTest.cmake b/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
index 25670bd..0ca9945 100644
--- a/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
@@ -187,7 +187,20 @@ endif ()
 if ("export_bmi" IN_LIST CMake_TEST_MODULE_COMPILATION)
   run_cxx_module_test(export-interface-no-properties-build)
   run_cxx_module_test(export-interface-build)
+  run_cxx_module_test(export-usage-build)
   run_cxx_module_test(export-bmi-and-interface-build)
+
+  if ("collation" IN_LIST CMake_TEST_MODULE_COMPILATION AND
+      "bmionly" IN_LIST CMake_TEST_MODULE_COMPILATION)
+    set(test_suffix export-interface-build)
+    run_cxx_module_test(import-modules "import-modules-${test_suffix}" "-DCMAKE_PREFIX_PATH=${RunCMake_BINARY_DIR}/examples/${test_suffix}-build")
+
+    set(test_suffix export-interface-no-properties-build)
+    run_cxx_module_test(import-modules "import-modules-${test_suffix}" "-DCMAKE_PREFIX_PATH=${RunCMake_BINARY_DIR}/examples/${test_suffix}-build" -DNO_PROPERTIES=1)
+
+    set(test_suffix export-bmi-and-interface-build)
+    run_cxx_module_test(import-modules "import-modules-${test_suffix}" "-DCMAKE_PREFIX_PATH=${RunCMake_BINARY_DIR}/examples/${test_suffix}-build" -DWITH_BMIS=1)
+  endif ()
 endif ()
 
 # All of the following tests perform installation.
@@ -201,6 +214,21 @@ 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)
+
+    if ("collation" IN_LIST CMake_TEST_MODULE_COMPILATION AND
+        "bmionly" IN_LIST CMake_TEST_MODULE_COMPILATION)
+      set(RunCMake_CXXModules_INSTALL 0)
+      set(test_suffix export-interface-install)
+      run_cxx_module_test(import-modules "import-modules-${test_suffix}" "-DCMAKE_PREFIX_PATH=${RunCMake_BINARY_DIR}/examples/${test_suffix}-install")
+
+      set(test_suffix export-interface-no-properties-install)
+      run_cxx_module_test(import-modules "import-modules-${test_suffix}" "-DCMAKE_PREFIX_PATH=${RunCMake_BINARY_DIR}/examples/${test_suffix}-install" -DNO_PROPERTIES=1)
+
+      set(test_suffix export-bmi-and-interface-install)
+      run_cxx_module_test(import-modules "import-modules-${test_suffix}" "-DCMAKE_PREFIX_PATH=${RunCMake_BINARY_DIR}/examples/${test_suffix}-install" -DWITH_BMIS=1)
+      set(RunCMake_CXXModules_INSTALL 1)
+    endif ()
   endif ()
 endif ()
diff --git a/Tests/RunCMake/CXXModules/examples/cxx-modules-rules.cmake b/Tests/RunCMake/CXXModules/examples/cxx-modules-rules.cmake
index 6238d37..5f32364 100644
--- a/Tests/RunCMake/CXXModules/examples/cxx-modules-rules.cmake
+++ b/Tests/RunCMake/CXXModules/examples/cxx-modules-rules.cmake
@@ -1,4 +1,4 @@
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 if (NOT EXISTS "${CMake_TEST_MODULE_COMPILATION_RULES}")
   message(FATAL_ERROR
diff --git a/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-build/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-build/test/CMakeLists.txt
index 4d7a85b..c17577c 100644
--- a/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-build/test/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-build/test/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.24)
 project(cxx_modules_library NONE)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 find_package(export_bmi_and_interfaces REQUIRED)
 
diff --git a/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-install/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-install/test/CMakeLists.txt
index b96328f..d608d67 100644
--- a/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-install/test/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-install/test/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.24)
 project(cxx_modules_library NONE)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 find_package(export_bmi_and_interfaces REQUIRED)
 
diff --git a/Tests/RunCMake/CXXModules/examples/export-interface-build/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-interface-build/test/CMakeLists.txt
index 74f16a6..106bd1e 100644
--- a/Tests/RunCMake/CXXModules/examples/export-interface-build/test/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModules/examples/export-interface-build/test/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.24)
 project(cxx_modules_library NONE)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 find_package(export_interfaces REQUIRED)
 
diff --git a/Tests/RunCMake/CXXModules/examples/export-interface-install/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-interface-install/test/CMakeLists.txt
index a4c9225..c19283b 100644
--- a/Tests/RunCMake/CXXModules/examples/export-interface-install/test/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModules/examples/export-interface-install/test/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.24)
 project(cxx_modules_library NONE)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 find_package(export_interfaces REQUIRED)
 
diff --git a/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-build/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-build/test/CMakeLists.txt
index 7f145ba2..fba05f4 100644
--- a/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-build/test/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-build/test/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.24)
 project(cxx_modules_library NONE)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 find_package(export_interfaces_no_properties REQUIRED)
 
diff --git a/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-install/test/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-install/test/CMakeLists.txt
index 7f145ba2..fba05f4 100644
--- a/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-install/test/CMakeLists.txt
+++ b/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-install/test/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.24)
 project(cxx_modules_library NONE)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 find_package(export_interfaces_no_properties REQUIRED)
 
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..8dfc41b
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-build/importable.cxx
@@ -0,0 +1,10 @@
+export module importable;
+
+extern "C++" {
+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..adec9e7
--- /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 "ac01f462-0f5f-432a-86aa-acef252918a6")
+
+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..8dfc41b
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/export-usage-install/importable.cxx
@@ -0,0 +1,10 @@
+export module importable;
+
+extern "C++" {
+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..9ccd63a
--- /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 "ac01f462-0f5f-432a-86aa-acef252918a6")
+
+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 ()
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules-export-bmi-and-interface-build-stderr.txt b/Tests/RunCMake/CXXModules/examples/import-modules-export-bmi-and-interface-build-stderr.txt
new file mode 100644
index 0000000..71ee795
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules-export-bmi-and-interface-build-stderr.txt
@@ -0,0 +1,7 @@
+CMake Warning \(dev\) at .*/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-build-build/export_bmi_and_interfaces-targets.cmake:[0-9]* \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+Call Stack \(most recent call first\):
+  .*/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-build-build/export_bmi_and_interfaces-config.cmake:1 \(include\)
+  CMakeLists.txt:15 \(find_package\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules-export-bmi-and-interface-install-stderr.txt b/Tests/RunCMake/CXXModules/examples/import-modules-export-bmi-and-interface-install-stderr.txt
new file mode 100644
index 0000000..d22b2a1
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules-export-bmi-and-interface-install-stderr.txt
@@ -0,0 +1,7 @@
+CMake Warning \(dev\) at .*/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-install-install/lib/cmake/export_bmi_and_interfaces/export_bmi_and_interfaces-targets.cmake:[0-9]* \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+Call Stack \(most recent call first\):
+  .*/Tests/RunCMake/CXXModules/examples/export-bmi-and-interface-install-install/lib/cmake/export_bmi_and_interfaces/export_bmi_and_interfaces-config.cmake:1 \(include\)
+  CMakeLists.txt:15 \(find_package\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-build-stderr.txt b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-build-stderr.txt
new file mode 100644
index 0000000..f79abbc
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-build-stderr.txt
@@ -0,0 +1,7 @@
+CMake Warning \(dev\) at .*/Tests/RunCMake/CXXModules/examples/export-interface-build-build/export_interfaces-targets.cmake:[0-9]* \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+Call Stack \(most recent call first\):
+  .*/Tests/RunCMake/CXXModules/examples/export-interface-build-build/export_interfaces-config.cmake:1 \(include\)
+  CMakeLists.txt:15 \(find_package\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-install-stderr.txt b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-install-stderr.txt
new file mode 100644
index 0000000..32f9452
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-install-stderr.txt
@@ -0,0 +1,7 @@
+CMake Warning \(dev\) at .*/Tests/RunCMake/CXXModules/examples/export-interface-install-install/lib/cmake/export_interfaces/export_interfaces-targets.cmake:[0-9]* \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+Call Stack \(most recent call first\):
+  .*/Tests/RunCMake/CXXModules/examples/export-interface-install-install/lib/cmake/export_interfaces/export_interfaces-config.cmake:1 \(include\)
+  CMakeLists.txt:15 \(find_package\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-no-properties-build-stderr.txt b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-no-properties-build-stderr.txt
new file mode 100644
index 0000000..9254936
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-no-properties-build-stderr.txt
@@ -0,0 +1,7 @@
+CMake Warning \(dev\) at .*/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-build-build/export_interfaces_no_properties-targets.cmake:[0-9]* \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+Call Stack \(most recent call first\):
+  .*/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-build-build/export_interfaces_no_properties-config.cmake:1 \(include\)
+  CMakeLists.txt:15 \(find_package\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-no-properties-install-stderr.txt b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-no-properties-install-stderr.txt
new file mode 100644
index 0000000..71269f4
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules-export-interface-no-properties-install-stderr.txt
@@ -0,0 +1,7 @@
+CMake Warning \(dev\) at .*/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-install-install/lib/cmake/export_interfaces_no_properties/export_interfaces_no_properties-targets.cmake:[0-9]* \(target_sources\):
+  CMake's C\+\+ module support is experimental.  It is meant only for
+  experimentation and feedback to CMake developers.
+Call Stack \(most recent call first\):
+  .*/Tests/RunCMake/CXXModules/examples/export-interface-no-properties-install-install/lib/cmake/export_interfaces_no_properties/export_interfaces_no_properties-config.cmake:1 \(include\)
+  CMakeLists.txt:15 \(find_package\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/import-modules/CMakeLists.txt
new file mode 100644
index 0000000..3e6f379
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules/CMakeLists.txt
@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.24)
+project(cxx_modules_import_interfaces CXX)
+
+include("${CMAKE_SOURCE_DIR}/../cxx-modules-rules.cmake")
+
+if (NO_PROPERTIES)
+  set(package_name "export_interfaces_no_properties")
+elseif (WITH_BMIS)
+  set(package_name "export_bmi_and_interfaces")
+else ()
+  set(package_name "export_interfaces")
+endif ()
+set(target_name "CXXModules::${package_name}")
+
+find_package("${package_name}" REQUIRED)
+
+add_executable(use_import_interfaces)
+target_sources(use_import_interfaces
+  PRIVATE
+    use.cxx)
+target_compile_features(use_import_interfaces PRIVATE cxx_std_20)
+target_link_libraries(use_import_interfaces PRIVATE "${target_name}")
+
+add_test(NAME use_import_interfaces COMMAND use_import_interfaces)
diff --git a/Tests/RunCMake/CXXModules/examples/import-modules/use.cxx b/Tests/RunCMake/CXXModules/examples/import-modules/use.cxx
new file mode 100644
index 0000000..feb38d2
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/import-modules/use.cxx
@@ -0,0 +1,6 @@
+import importable;
+
+int main(int argc, char* argv[])
+{
+  return from_import();
+}
diff --git a/Tests/RunCMake/target_sources/FileSetDefaultWrongTypeExperimental.cmake b/Tests/RunCMake/target_sources/FileSetDefaultWrongTypeExperimental.cmake
index 0826686..9a8429d 100644
--- a/Tests/RunCMake/target_sources/FileSetDefaultWrongTypeExperimental.cmake
+++ b/Tests/RunCMake/target_sources/FileSetDefaultWrongTypeExperimental.cmake
@@ -1,6 +1,6 @@
 enable_language(C)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 add_library(lib1 STATIC empty.c)
 target_sources(lib1 PRIVATE FILE_SET UNKNOWN)
diff --git a/Tests/RunCMake/target_sources/FileSetWrongTypeExperimental.cmake b/Tests/RunCMake/target_sources/FileSetWrongTypeExperimental.cmake
index 7935178..f63308c 100644
--- a/Tests/RunCMake/target_sources/FileSetWrongTypeExperimental.cmake
+++ b/Tests/RunCMake/target_sources/FileSetWrongTypeExperimental.cmake
@@ -1,6 +1,6 @@
 enable_language(C)
 
-set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "a816ed09-43d1-40e5-bc8c-1a2824ee194e")
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API "ac01f462-0f5f-432a-86aa-acef252918a6")
 
 add_library(lib1 STATIC empty.c)
 target_sources(lib1 PRIVATE FILE_SET a TYPE UNKNOWN)