target_link_libraries: Allow use with targets in other directories

Previously the command did not allow naming targets on the LHS that
were not created in the calling directory.  Lift this restriction to
enable more flexible use by projects.

Fixes: #17943

19 files changed, 110 insertions, 10 deletions

diff --git a/Copyright.txt b/Copyright.txt
index 660455f619..743c63418e 100644
--- a/Copyright.txt
+++ b/Copyright.txt
@@ -78,6 +78,7 @@ The following individuals and institutions are among the Contributors:
 * Nikita Krupen'ko <krnekit@gmail.com>
 * NVIDIA Corporation <www.nvidia.com>
 * OpenGamma Ltd. <opengamma.com>
+* Patrick Stotko <stotko@cs.uni-bonn.de>
 * Per Øyvind Karlsen <peroyvind@mandriva.org>
 * Peter Collingbourne <peter@pcc.me.uk>
 * Petr Gotthard <gotthard@honeywell.com>
diff --git a/Help/command/target_link_libraries.rst b/Help/command/target_link_libraries.rst
index fcc2c0745d..6379730d81 100644
--- a/Help/command/target_link_libraries.rst
+++ b/Help/command/target_link_libraries.rst
@@ -18,7 +18,7 @@ All of them have the general form::
 
   target_link_libraries(<target> ... <item>... ...)
 
-The named ``<target>`` must have been created in the current directory by
+The named ``<target>`` must have been created by
 a command such as :command:`add_executable` or :command:`add_library` and
 must not be an :ref:`ALIAS target <Alias Targets>`.
 Repeated calls for the same ``<target>`` append items in the order called.
diff --git a/Help/release/dev/subdirectory-linking.rst b/Help/release/dev/subdirectory-linking.rst
new file mode 100644
index 0000000000..1909c36558
--- /dev/null
+++ b/Help/release/dev/subdirectory-linking.rst
@@ -0,0 +1,5 @@
+subdirectory-linking
+--------------------
+
+* The :command:`target_link_libraries` command may now be called
+  to modify targets created outside the current directory.
diff --git a/Source/cmTargetLinkLibrariesCommand.cxx b/Source/cmTargetLinkLibrariesCommand.cxx
index 699fff8b8b..53f1213e88 100644
--- a/Source/cmTargetLinkLibrariesCommand.cxx
+++ b/Source/cmTargetLinkLibrariesCommand.cxx
@@ -364,7 +364,7 @@ bool cmTargetLinkLibrariesCommand::HandleLibrary(const std::string& lib,
   if (this->CurrentProcessingState != ProcessingKeywordLinkInterface &&
       this->CurrentProcessingState != ProcessingPlainLinkInterface) {
 
-    // Assure that the target on the LHS was created in the current directory.
+    // Find target on the LHS locally
     cmTarget* t =
       this->Makefile->FindLocalNonAliasTarget(this->Target->GetName());
     if (!t) {
@@ -377,11 +377,18 @@ bool cmTargetLinkLibrariesCommand::HandleLibrary(const std::string& lib,
         }
       }
     }
+
+    // If no local target has been found, find it in the global scope
+    if (!t) {
+      t = this->Makefile->GetGlobalGenerator()->FindTarget(
+        this->Target->GetName(), true);
+    }
+
     if (!t) {
       std::ostringstream e;
       e << "Attempt to add link library \"" << lib << "\" to target \""
         << this->Target->GetName()
-        << "\" which is not built in this directory.";
+        << "\" which does not exist or is an alias target.";
       this->Makefile->IssueMessage(cmake::FATAL_ERROR, e.str());
       return false;
     }
diff --git a/Tests/RunCMake/target_link_libraries/RunCMakeTest.cmake b/Tests/RunCMake/target_link_libraries/RunCMakeTest.cmake
index 97b0888a7e..d61fa5f8cf 100644
--- a/Tests/RunCMake/target_link_libraries/RunCMakeTest.cmake
+++ b/Tests/RunCMake/target_link_libraries/RunCMakeTest.cmake
@@ -8,7 +8,10 @@ run_cmake(ImportedTarget)
 run_cmake(ImportedTargetFailure)
 run_cmake(MixedSignature)
 run_cmake(Separate-PRIVATE-LINK_PRIVATE-uses)
+run_cmake(SubDirImportedTarget)
 run_cmake(SubDirTarget)
+run_cmake(SubDirTarget-UNKNOWN-IMPORTED)
+run_cmake(SubDirTarget-UNKNOWN-IMPORTED-GLOBAL)
 run_cmake(SharedDepNotTarget)
 run_cmake(StaticPrivateDepNotExported)
 run_cmake(StaticPrivateDepNotTarget)
diff --git a/Tests/RunCMake/target_link_libraries/SubDirImportedTarget-stdout.txt b/Tests/RunCMake/target_link_libraries/SubDirImportedTarget-stdout.txt
new file mode 100644
index 0000000000..a7ef260e61
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirImportedTarget-stdout.txt
@@ -0,0 +1,4 @@
+-- mainexeUnknownImportedGlobal: mainlib;sublib
+-- mainlibUnknownImportedGlobal: mainlib;sublib
+-- subexeUnknownImportedGlobal: mainlib;sublib
+-- sublibUnknownImportedGlobal: mainlib;sublib
diff --git a/Tests/RunCMake/target_link_libraries/SubDirImportedTarget.cmake b/Tests/RunCMake/target_link_libraries/SubDirImportedTarget.cmake
new file mode 100644
index 0000000000..738280be1b
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirImportedTarget.cmake
@@ -0,0 +1,17 @@
+enable_language(C)
+
+add_executable(mainexeUnknownImportedGlobal IMPORTED GLOBAL)
+add_library(mainlibUnknownImportedGlobal UNKNOWN IMPORTED GLOBAL)
+add_library(mainlib empty.c)
+
+add_subdirectory(SubDirImportedTarget)
+
+target_link_libraries(subexeUnknownImportedGlobal INTERFACE mainlib)
+target_link_libraries(subexeUnknownImportedGlobal INTERFACE sublib)
+get_property(subexeUnknownImportedGlobal_libs TARGET subexeUnknownImportedGlobal PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "subexeUnknownImportedGlobal: ${subexeUnknownImportedGlobal_libs}")
+
+target_link_libraries(sublibUnknownImportedGlobal INTERFACE mainlib)
+target_link_libraries(sublibUnknownImportedGlobal INTERFACE sublib)
+get_property(sublibUnknownImportedGlobal_libs TARGET sublibUnknownImportedGlobal PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "sublibUnknownImportedGlobal: ${sublibUnknownImportedGlobal_libs}")
diff --git a/Tests/RunCMake/target_link_libraries/SubDirImportedTarget/CMakeLists.txt b/Tests/RunCMake/target_link_libraries/SubDirImportedTarget/CMakeLists.txt
new file mode 100644
index 0000000000..d67a01cb6e
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirImportedTarget/CMakeLists.txt
@@ -0,0 +1,13 @@
+add_executable(subexeUnknownImportedGlobal IMPORTED GLOBAL)
+add_library(sublibUnknownImportedGlobal UNKNOWN IMPORTED GLOBAL)
+add_library(sublib ../empty.c)
+
+target_link_libraries(mainexeUnknownImportedGlobal INTERFACE mainlib)
+target_link_libraries(mainexeUnknownImportedGlobal INTERFACE sublib)
+get_property(mainexeUnknownImportedGlobal_libs TARGET mainexeUnknownImportedGlobal PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "mainexeUnknownImportedGlobal: ${mainexeUnknownImportedGlobal_libs}")
+
+target_link_libraries(mainlibUnknownImportedGlobal INTERFACE mainlib)
+target_link_libraries(mainlibUnknownImportedGlobal INTERFACE sublib)
+get_property(mainlibUnknownImportedGlobal_libs TARGET mainlibUnknownImportedGlobal PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "mainlibUnknownImportedGlobal: ${mainlibUnknownImportedGlobal_libs}")
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL-stdout.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL-stdout.txt
new file mode 100644
index 0000000000..a8c77cbbe0
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL-stdout.txt
@@ -0,0 +1,2 @@
+-- mainexe: mainlibUnknownImportedGlobal;sublibUnknownImportedGlobal
+-- subexe: mainlibUnknownImportedGlobal;sublibUnknownImportedGlobal
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL.cmake b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL.cmake
new file mode 100644
index 0000000000..04d64e6529
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL.cmake
@@ -0,0 +1,11 @@
+enable_language(C)
+
+add_executable(mainexe empty.c)
+add_library(mainlibUnknownImportedGlobal UNKNOWN IMPORTED GLOBAL)
+
+add_subdirectory(SubDirTarget-UNKNOWN-IMPORTED-GLOBAL)
+
+target_link_libraries(subexe mainlibUnknownImportedGlobal)
+target_link_libraries(subexe sublibUnknownImportedGlobal)
+get_property(subexe_libs TARGET subexe PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "subexe: ${subexe_libs}")
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL/CMakeLists.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL/CMakeLists.txt
new file mode 100644
index 0000000000..6c0c8b20c4
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-GLOBAL/CMakeLists.txt
@@ -0,0 +1,7 @@
+add_executable(subexe ../empty.c)
+add_library(sublibUnknownImportedGlobal UNKNOWN IMPORTED GLOBAL)
+
+target_link_libraries(mainexe mainlibUnknownImportedGlobal)
+target_link_libraries(mainexe sublibUnknownImportedGlobal)
+get_property(mainexe_libs TARGET mainexe PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "mainexe: ${mainexe_libs}")
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-stdout.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-stdout.txt
new file mode 100644
index 0000000000..4980dc925a
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED-stdout.txt
@@ -0,0 +1,2 @@
+-- mainexe: mainlibUnknownImported;sublibUnknownImported
+-- subexe: mainlibUnknownImported;sublibUnknownImported
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED.cmake b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED.cmake
new file mode 100644
index 0000000000..e476a3f0cd
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED.cmake
@@ -0,0 +1,11 @@
+enable_language(C)
+
+add_executable(mainexe empty.c)
+add_library(mainlibUnknownImported UNKNOWN IMPORTED)
+
+add_subdirectory(SubDirTarget-UNKNOWN-IMPORTED)
+
+target_link_libraries(subexe mainlibUnknownImported)
+target_link_libraries(subexe sublibUnknownImported)
+get_property(subexe_libs TARGET subexe PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "subexe: ${subexe_libs}")
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED/CMakeLists.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED/CMakeLists.txt
new file mode 100644
index 0000000000..4a40a68aef
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget-UNKNOWN-IMPORTED/CMakeLists.txt
@@ -0,0 +1,7 @@
+add_executable(subexe ../empty.c)
+add_library(sublibUnknownImported UNKNOWN IMPORTED)
+
+target_link_libraries(mainexe mainlibUnknownImported)
+target_link_libraries(mainexe sublibUnknownImported)
+get_property(mainexe_libs TARGET mainexe PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "mainexe: ${mainexe_libs}")
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-result.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget-result.txt
deleted file mode 100644
index d00491fd7e..0000000000
--- a/Tests/RunCMake/target_link_libraries/SubDirTarget-result.txt
+++ /dev/null
@@ -1 +0,0 @@
-1
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-stderr.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget-stderr.txt
deleted file mode 100644
index 5cd1f23d7b..0000000000
--- a/Tests/RunCMake/target_link_libraries/SubDirTarget-stderr.txt
+++ /dev/null
@@ -1,5 +0,0 @@
-^CMake Error at SubDirTarget.cmake:[0-9]+ \(target_link_libraries\):
-  Attempt to add link library "m" to target "subexe" which is not built in
-  this directory.
-Call Stack \(most recent call first\):
-  CMakeLists.txt:[0-9]+ \(include\)$
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget-stdout.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget-stdout.txt
new file mode 100644
index 0000000000..646f984279
--- /dev/null
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget-stdout.txt
@@ -0,0 +1,2 @@
+-- mainexe: mainlib;sublib
+-- subexe: mainlib;sublib
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget.cmake b/Tests/RunCMake/target_link_libraries/SubDirTarget.cmake
index 32431cecc0..55c658dc76 100644
--- a/Tests/RunCMake/target_link_libraries/SubDirTarget.cmake
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget.cmake
@@ -1,3 +1,11 @@
 enable_language(C)
+
+add_executable(mainexe empty.c)
+add_library(mainlib empty.c)
+
 add_subdirectory(SubDirTarget)
-target_link_libraries(subexe m)
+
+target_link_libraries(subexe mainlib)
+target_link_libraries(subexe sublib)
+get_property(subexe_libs TARGET subexe PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "subexe: ${subexe_libs}")
diff --git a/Tests/RunCMake/target_link_libraries/SubDirTarget/CMakeLists.txt b/Tests/RunCMake/target_link_libraries/SubDirTarget/CMakeLists.txt
index b0b23809a6..3d956a83d1 100644
--- a/Tests/RunCMake/target_link_libraries/SubDirTarget/CMakeLists.txt
+++ b/Tests/RunCMake/target_link_libraries/SubDirTarget/CMakeLists.txt
@@ -1 +1,7 @@
 add_executable(subexe ../empty.c)
+add_library(sublib ../empty.c)
+
+target_link_libraries(mainexe mainlib)
+target_link_libraries(mainexe sublib)
+get_property(mainexe_libs TARGET mainexe PROPERTY INTERFACE_LINK_LIBRARIES)
+message(STATUS "mainexe: ${mainexe_libs}")