export: Restore exclusion of private shared library dependencies from checks

Refactoring in commit 8c65b7042e (cmExportFileGenerator: Simplify
collection of targets missing from export set, 2022-04-11,
v3.24.0-rc1~281^2) accidentally dropped the behavior change from
commit 0ad2a1c181 (Export: Never treat private link libraries as
public package dependencies., 2013-09-24, v3.0.0-rc1~559^2).
Restore the behavior and add a test.

Fixes: #23838

Source/cmExportFileGenerator.cxx

@@ -843,9 +843,16 @@ void cmExportFileGenerator::SetImportDetailProperties(
       suffix, target, "IMPORTED_LINK_INTERFACE_LANGUAGES", iface->Languages,
       properties, ImportLinkPropertyTargetNames::No);
 
+    // Export IMPORTED_LINK_DEPENDENT_LIBRARIES to help consuming linkers
+    // find private dependencies of shared libraries.
+    std::size_t oldMissingTargetsSize = this->MissingTargets.size();
     this->SetImportLinkProperty(
       suffix, target, "IMPORTED_LINK_DEPENDENT_LIBRARIES", iface->SharedDeps,
       properties, ImportLinkPropertyTargetNames::Yes);
+    // Avoid enforcing shared library private dependencies as public package
+    // dependencies by ignoring missing targets added for them.
+    this->MissingTargets.resize(oldMissingTargetsSize);
+
     if (iface->Multiplicity > 0) {
       std::string prop =
         cmStrCat("IMPORTED_LINK_INTERFACE_MULTIPLICITY", suffix);

Tests/RunCMake/CMakeLists.txt

@@ -301,6 +301,7 @@ if("${CMAKE_GENERATOR}" MATCHES "Unix Makefiles|Ninja")
   add_RunCMake_test(ExportCompileCommands)
 endif()
 add_RunCMake_test(ExcludeFromAll)
+add_RunCMake_test(ExportImport)
 add_RunCMake_test(ExternalData)
 add_RunCMake_test(FeatureSummary)
 add_RunCMake_test(FPHSA)

Tests/RunCMake/ExportImport/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 3.23)
+project(${RunCMake_TEST} NONE)
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/ExportImport/RunCMakeTest.cmake

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.23)
+include(RunCMake)
+
+function(run_ExportImport_test case)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/${case}-export-build)
+  set(CMAKE_INSTALL_PREFIX ${RunCMake_TEST_BINARY_DIR}/root)
+  if (NOT RunCMake_GENERATOR_IS_MULTI_CONFIG)
+    set(RunCMake_TEST_OPTIONS -DCMAKE_BUILD_TYPE=Debug)
+  endif()
+  run_cmake(${case}-export)
+  unset(RunCMake_TEST_OPTIONS)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  run_cmake_command(${case}-export-build ${CMAKE_COMMAND} --build . --config Debug)
+  run_cmake_command(${case}-export-install ${CMAKE_COMMAND} -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX} -DBUILD_TYPE=Debug -P cmake_install.cmake)
+  unset(RunCMake_TEST_NO_CLEAN)
+
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/${case}-import-build)
+  run_cmake_with_options(${case}-import
+    -Dfoo_DIR=${CMAKE_INSTALL_PREFIX}/lib/cmake/foo
+    -Dbar_DIR=${CMAKE_INSTALL_PREFIX}/lib/cmake/bar
+    )
+endfunction()
+
+run_ExportImport_test(SharedDep)

Tests/RunCMake/ExportImport/SharedDep-export.cmake

@@ -0,0 +1,13 @@
+enable_language(C)
+
+add_library(foo SHARED foo.c)
+install(TARGETS foo EXPORT foo)
+install(EXPORT foo DESTINATION lib/cmake/foo)
+install(FILES foo-config.cmake.in RENAME foo-config.cmake DESTINATION lib/cmake/foo)
+
+add_library(bar SHARED bar.c)
+target_link_libraries(bar PRIVATE foo)
+# 'foo' only appears in IMPORTED_LINK_DEPENDENT_LIBRARIES, and so is not enforced on import.
+install(TARGETS bar EXPORT bar)
+install(EXPORT bar DESTINATION lib/cmake/bar)
+install(FILES bar-config.cmake.in RENAME bar-config.cmake DESTINATION lib/cmake/bar)

Tests/RunCMake/ExportImport/SharedDep-import.cmake

@@ -0,0 +1 @@
+find_package(bar REQUIRED CONFIG NO_DEFAULT_PATH)

Tests/RunCMake/ExportImport/bar-config.cmake.in

@@ -0,0 +1,2 @@
+# find_dependency(foo) intentionally left out for this test case
+include(${CMAKE_CURRENT_LIST_DIR}/bar.cmake)

Tests/RunCMake/ExportImport/bar.c

@@ -0,0 +1,12 @@
+#if defined(_WIN32)
+__declspec(dllimport)
+#endif
+  int foo(void);
+
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+  int bar(void)
+{
+  return foo();
+}

Tests/RunCMake/ExportImport/foo-config.cmake.in

@@ -0,0 +1 @@
+include(${CMAKE_CURRENT_LIST_DIR}/foo.cmake)

Tests/RunCMake/ExportImport/foo.c

@@ -0,0 +1,7 @@
+#ifdef _WIN32
+__declspec(dllexport)
+#endif
+  int foo(void)
+{
+  return 0;
+}