Add new target-property `IMPORTED_GLOBAL`.

The purpose of this new `IMPORTED_GLOBAL` target-property is to prolong
the lifetime and scope of `IMPORTED` targets in such a way as if they
had been created with the keyword `GLOBAL` in the first place.

* It can only be set to `TRUE`. That means, a local `IMPORTED` target
  can be promoted to global scope but a global `IMPORTED` target cannot
  be degraded to local scope!
* Setting it to `TRUE` only succeeds if done from within the same
  directory in which the `IMPORTED` target was created in the first
  place.

Fixes #17256.

9 files changed, 155 insertions, 1 deletions

diff --git a/Tests/RunCMake/get_property/target_properties-stderr.txt b/Tests/RunCMake/get_property/target_properties-stderr.txt
index 6b3c6ca..df7a2f1 100644
--- a/Tests/RunCMake/get_property/target_properties-stderr.txt
+++ b/Tests/RunCMake/get_property/target_properties-stderr.txt
@@ -7,4 +7,10 @@ get_property: --><--
 get_target_property: -->(.*)/Tests/RunCMake/get_property<--
 get_property: -->(.*)/Tests/RunCMake/get_property<--
 get_target_property: -->(.*)/Tests/RunCMake/get_property/target_properties-build<--
-get_property: -->(.*)/Tests/RunCMake/get_property/target_properties-build<--$
+get_property: -->(.*)/Tests/RunCMake/get_property/target_properties-build<--
+get_target_property: -->FALSE<--
+get_property: -->FALSE<--
+get_target_property: -->FALSE<--
+get_property: -->FALSE<--
+get_target_property: -->TRUE<--
+get_property: -->TRUE<--$
diff --git a/Tests/RunCMake/get_property/target_properties.cmake b/Tests/RunCMake/get_property/target_properties.cmake
index 9ff833a..321d5b5 100644
--- a/Tests/RunCMake/get_property/target_properties.cmake
+++ b/Tests/RunCMake/get_property/target_properties.cmake
@@ -16,3 +16,10 @@ check_target_property(tgt custom)
 check_target_property(tgt noexist)
 check_target_property(tgt SOURCE_DIR)
 check_target_property(tgt BINARY_DIR)
+
+add_library(imported_local_tgt SHARED IMPORTED)
+add_library(imported_global_tgt SHARED IMPORTED GLOBAL)
+
+check_target_property(tgt IMPORTED_GLOBAL)
+check_target_property(imported_local_tgt IMPORTED_GLOBAL)
+check_target_property(imported_global_tgt IMPORTED_GLOBAL)
diff --git a/Tests/RunCMake/set_property/IMPORTED_GLOBAL-result.txt b/Tests/RunCMake/set_property/IMPORTED_GLOBAL-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/set_property/IMPORTED_GLOBAL-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/set_property/IMPORTED_GLOBAL-stderr.txt b/Tests/RunCMake/set_property/IMPORTED_GLOBAL-stderr.txt
new file mode 100644
index 0000000..f21b1de
--- /dev/null
+++ b/Tests/RunCMake/set_property/IMPORTED_GLOBAL-stderr.txt
@@ -0,0 +1,61 @@
+^CMake Error at IMPORTED_GLOBAL.cmake:9 \(set_property\):
+  IMPORTED_GLOBAL property can't be set to FALSE on targets
+  \(\"ImportedGlobalTarget\"\)
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error at IMPORTED_GLOBAL.cmake:16 \(set_property\):
+  IMPORTED_GLOBAL property can't be appended, only set on imported targets
+  \(\"ImportedGlobalTarget\"\)
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error at IMPORTED_GLOBAL.cmake:26 \(set_property\):
+  IMPORTED_GLOBAL property can't be set to FALSE on targets
+  \(\"ImportedLocalTarget\"\)
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error at IMPORTED_GLOBAL.cmake:32 \(set_property\):
+  IMPORTED_GLOBAL property can't be set on non-imported targets
+  \(\"NonImportedTarget\"\)
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error at IMPORTED_GLOBAL/CMakeLists.txt:8 \(set_property\):
+  Attempt to promote imported target \"ImportedLocalTarget2\" to global scope
+  \(by setting IMPORTED_GLOBAL\) which is not built in this directory.
+
+
+CMake Error in IMPORTED_GLOBAL/CMakeLists.txt:
+  IMPORTED_GLOBAL property can't be set to FALSE on targets
+  \(\"ImportedSubdirTarget1\"\)
+
+
+
+CMake Error at IMPORTED_GLOBAL.cmake:50 \(set_property\):
+  Attempt to promote imported target \"ImportedSubdirTarget1\" to global scope
+  \(by setting IMPORTED_GLOBAL\) which is not built in this directory.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+
+
+CMake Error in IMPORTED_GLOBAL/CMakeLists.txt:
+  IMPORTED_GLOBAL property can't be set to FALSE on targets
+  \(\"ImportedSubdirTarget2\"\)
+
+
+
+CMake Error at IMPORTED_GLOBAL.cmake:52 \(set_property\):
+  Attempt to promote imported target \"ImportedSubdirTarget2\" to global scope
+  \(by setting IMPORTED_GLOBAL\) which is not built in this directory.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)$
diff --git a/Tests/RunCMake/set_property/IMPORTED_GLOBAL-stdout.txt b/Tests/RunCMake/set_property/IMPORTED_GLOBAL-stdout.txt
new file mode 100644
index 0000000..c5f1d11
--- /dev/null
+++ b/Tests/RunCMake/set_property/IMPORTED_GLOBAL-stdout.txt
@@ -0,0 +1,17 @@
+-- ImportedGlobalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedGlobalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedGlobalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedGlobalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedGlobalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedLocalTarget: Target IMPORTED_GLOBAL is 'FALSE'
+-- ImportedLocalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedLocalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedLocalTarget: Target IMPORTED_GLOBAL is 'TRUE'
+-- NonImportedTarget: Target IMPORTED_GLOBAL is 'FALSE'
+-- NonImportedTarget: Target IMPORTED_GLOBAL is 'FALSE'
+-- ImportedLocalTarget2: Target IMPORTED_GLOBAL is 'FALSE'
+-- ImportedLocalTarget2: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedSubdirTarget1: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedSubdirTarget2: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedSubdirTarget1: Target IMPORTED_GLOBAL is 'TRUE'
+-- ImportedSubdirTarget2: Target IMPORTED_GLOBAL is 'TRUE'
diff --git a/Tests/RunCMake/set_property/IMPORTED_GLOBAL.cmake b/Tests/RunCMake/set_property/IMPORTED_GLOBAL.cmake
new file mode 100644
index 0000000..08308eb
--- /dev/null
+++ b/Tests/RunCMake/set_property/IMPORTED_GLOBAL.cmake
@@ -0,0 +1,53 @@
+macro(print_property TARGET PROP)
+  get_property(val TARGET ${TARGET} PROPERTY ${PROP})
+  message(STATUS "${TARGET}: Target ${PROP} is '${val}'")
+endmacro()
+
+# Changing property on IMPORTED target created with `GLOBAL` option.
+add_library(ImportedGlobalTarget SHARED IMPORTED GLOBAL)
+print_property(ImportedGlobalTarget IMPORTED_GLOBAL)
+set_property(TARGET ImportedGlobalTarget PROPERTY IMPORTED_GLOBAL FALSE)
+print_property(ImportedGlobalTarget IMPORTED_GLOBAL)
+set_property(TARGET ImportedGlobalTarget PROPERTY IMPORTED_GLOBAL TRUE)
+print_property(ImportedGlobalTarget IMPORTED_GLOBAL)
+set_property(TARGET ImportedGlobalTarget PROPERTY IMPORTED_GLOBAL TRUE)
+print_property(ImportedGlobalTarget IMPORTED_GLOBAL)
+# Appending property is never allowed!
+set_property(TARGET ImportedGlobalTarget APPEND PROPERTY IMPORTED_GLOBAL TRUE)
+print_property(ImportedGlobalTarget IMPORTED_GLOBAL)
+
+# Changing property on IMPORTED target created without `GLOBAL` option.
+add_library(ImportedLocalTarget SHARED IMPORTED)
+print_property(ImportedLocalTarget IMPORTED_GLOBAL)
+set_property(TARGET ImportedLocalTarget PROPERTY IMPORTED_GLOBAL TRUE)
+print_property(ImportedLocalTarget IMPORTED_GLOBAL)
+set_property(TARGET ImportedLocalTarget PROPERTY IMPORTED_GLOBAL TRUE)
+print_property(ImportedLocalTarget IMPORTED_GLOBAL)
+set_property(TARGET ImportedLocalTarget PROPERTY IMPORTED_GLOBAL FALSE)
+print_property(ImportedLocalTarget IMPORTED_GLOBAL)
+
+# Setting property on non-IMPORTED target is never allowed!
+add_library(NonImportedTarget SHARED test.cpp)
+print_property(NonImportedTarget IMPORTED_GLOBAL)
+set_property(TARGET NonImportedTarget PROPERTY IMPORTED_GLOBAL TRUE)
+print_property(NonImportedTarget IMPORTED_GLOBAL)
+
+# Local IMPORTED targets can only be promoted from same directory!
+add_library(ImportedLocalTarget2 SHARED IMPORTED)
+print_property(ImportedLocalTarget2 IMPORTED_GLOBAL)
+add_subdirectory(IMPORTED_GLOBAL)
+# Note: The value should not have changed. However, it does change because the
+# check for the same directory comes after it was changed! (At least, that is
+# not really bad because the generation will fail due to this error.)
+print_property(ImportedLocalTarget2 IMPORTED_GLOBAL)
+
+# Global IMPORTED targets from subdir are always visible
+# no matter how they became global.
+print_property(ImportedSubdirTarget1 IMPORTED_GLOBAL)
+print_property(ImportedSubdirTarget2 IMPORTED_GLOBAL)
+
+# Changing property on IMPORTED target from subdir is never possible.
+set_property(TARGET ImportedSubdirTarget1 PROPERTY IMPORTED_GLOBAL FALSE)
+print_property(ImportedSubdirTarget1 IMPORTED_GLOBAL)
+set_property(TARGET ImportedSubdirTarget2 PROPERTY IMPORTED_GLOBAL FALSE)
+print_property(ImportedSubdirTarget2 IMPORTED_GLOBAL)
diff --git a/Tests/RunCMake/set_property/IMPORTED_GLOBAL/CMakeLists.txt b/Tests/RunCMake/set_property/IMPORTED_GLOBAL/CMakeLists.txt
new file mode 100644
index 0000000..468bf78
--- /dev/null
+++ b/Tests/RunCMake/set_property/IMPORTED_GLOBAL/CMakeLists.txt
@@ -0,0 +1,8 @@
+add_library(ImportedSubdirTarget1 SHARED IMPORTED GLOBAL)
+add_library(ImportedSubdirTarget2 SHARED IMPORTED)
+
+# Extend visibility of ImportedSubdirTarget2 to global scope.
+set_property(TARGET ImportedSubdirTarget2 PROPERTY IMPORTED_GLOBAL TRUE)
+
+# Only targets from the same directory can be promoted.
+set_property(TARGET ImportedLocalTarget2 PROPERTY IMPORTED_GLOBAL TRUE)
diff --git a/Tests/RunCMake/set_property/RunCMakeTest.cmake b/Tests/RunCMake/set_property/RunCMakeTest.cmake
index 1ddacee..5b5327d 100644
--- a/Tests/RunCMake/set_property/RunCMakeTest.cmake
+++ b/Tests/RunCMake/set_property/RunCMakeTest.cmake
@@ -3,6 +3,7 @@ include(RunCMake)
 run_cmake(COMPILE_DEFINITIONS)
 run_cmake(COMPILE_FEATURES)
 run_cmake(COMPILE_OPTIONS)
+run_cmake(IMPORTED_GLOBAL)
 run_cmake(INCLUDE_DIRECTORIES)
 run_cmake(LINK_LIBRARIES)
 run_cmake(SOURCES)
diff --git a/Tests/RunCMake/set_property/test.cpp b/Tests/RunCMake/set_property/test.cpp
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/Tests/RunCMake/set_property/test.cpp