ALIAS: Add support for install and export commands

The install({TARGETS, EXPORT}) versions of the command now accept ALIAS
targets. The behavior is identical to what would happen if the name of
the target that the ALIAS references were put instead. The
export(TARGETS) command also has the same support and behavior for ALIAS
targets now.

Closes: #20979

Help/command/add_executable.rst

@@ -112,13 +112,15 @@ Alias Executables
 ``ALIAS`` targets can be used as targets to read properties
 from, executables for custom commands and custom targets.  They can also be
 tested for existence with the regular :command:`if(TARGET)` subcommand.
-An ``ALIAS`` target may not be installed or exported.
 
 .. versionchanged:: 4.5
   The ``<name>`` may be used as the operand of :command:`set_property`,
   :command:`set_target_properties`, :command:`target_link_libraries`, etc. to
-  modify properties of ``<target>``.  CMake 4.4 and earlier did not allow the
-  ``<name>`` to modify properties of ``<target>``.
+  modify properties of ``<target>``.  If an ``ALIAS`` executable is passed to
+  an :command:`install` or :command:`export` command, the executable that the
+  alias references is installed or exported.  CMake 4.4 and earlier did not
+  allow using the ``<name>`` to modify properties of ``<target>``, or using
+  the ``<name>`` in :command:`install` and :command:`export` commands.
 
 See Also
 ^^^^^^^^

Help/command/add_library.rst

@@ -317,14 +317,16 @@ Alias Libraries
 
 ``ALIAS`` targets can be used as linkable targets and as targets to
 read properties from.  They can also be tested for existence with the
-regular :command:`if(TARGET)` subcommand.  An ``ALIAS`` target may not be
-installed or exported.
+regular :command:`if(TARGET)` subcommand.
 
 .. versionchanged:: 4.5
   The ``<name>`` may be used as the operand of :command:`set_property`,
   :command:`set_target_properties`, :command:`target_link_libraries`, etc. to
-  modify properties of ``<target>``.  CMake 4.4 and earlier did not allow the
-  ``<name>`` to modify properties of ``<target>``.
+  modify properties of ``<target>``.  If an ``ALIAS`` target is passed to an
+  :command:`install` or :command:`export` command, the target that the alias
+  references is installed or exported.  CMake 4.4 and earlier did not allow
+  using the ``<name>`` to modify properties of ``<target>``, or using the
+  ``<name>`` in :command:`install` and :command:`export` commands.
 
 See Also
 ^^^^^^^^

Help/manual/cmake-buildsystem.7.rst

@@ -1433,9 +1433,11 @@ entirely local to the buildsystem description.
 
 .. versionchanged:: 4.5
   ``ALIAS`` targets may be used as the operand for :command:`set_property` and
-  similar commands used to modify properties of targets.  The commands operate
-  on the target which the alias references.  CMake 4.4 and earlier did not
-  allow modifying targets via an ``ALIAS``.
+  similar commands used to modify properties of targets.  The
+  :command:`install` and :command:`export` commands may also use an ``ALIAS``
+  target as the operand.  The commands operate on the target which the alias
+  references.  CMake 4.4 and earlier did not allow modifying, installing,
+  or exporting targets via an ``ALIAS``.
 
 A name can be tested for whether it is an ``ALIAS`` name by reading the
 :prop_tgt:`ALIASED_TARGET` property from it:

Help/release/dev/alias-transparency-install.rst

@@ -0,0 +1,6 @@
+alias-transparency-install
+--------------------------
+
+* The :command:`export` and :command:`install` commands now
+  accept :ref:`Alias Targets`. The commands operate on the underlying
+  aliased target.

Source/cmExportCommand.cxx

@@ -89,15 +89,10 @@ static void AddExportGenerator(
   makefile.AddExportBuildFileGenerator(std::move(exportGenerator));
 }
 
-static bool ValidateExportableTarget(std::string const& name, cmMakefile& mf,
+static bool ValidateExportableTarget(std::string const& name,
                                      cmGlobalGenerator* gg,
                                      cmExecutionStatus& status)
 {
-  if (mf.IsAlias(name)) {
-    status.SetError(cmStrCat("given ALIAS target \"", name,
-                             "\" which may not be exported."));
-    return false;
-  }
   cmTarget const* target = gg->FindTarget(name);
   if (!target) {
     status.SetError(cmStrCat("given target \"", name,
@@ -187,7 +182,7 @@ static bool HandleTargetsMode(std::vector<std::string> const& args,
   cmGlobalGenerator* gg = mf.GetGlobalGenerator();
 
   for (std::string const& currentTarget : *arguments.Targets) {
-    if (!ValidateExportableTarget(currentTarget, mf, gg, status)) {
+    if (!ValidateExportableTarget(currentTarget, gg, status)) {
       return false;
     }
     targets.emplace_back(currentTarget, std::string{});

Source/cmInstallCommand.cxx

@@ -704,18 +704,12 @@ bool HandleTargetsMode(std::vector<std::string> const& args,
 
   for (std::string const& tgt : targetList) {
 
-    if (helper.Makefile->IsAlias(tgt)) {
-      status.SetError(
-        cmStrCat("TARGETS given target \"", tgt, "\" which is an alias."));
-      return false;
-    }
     // Lookup this target in the current directory.
     cmTarget* target = helper.Makefile->FindLocalNonAliasTarget(tgt);
     if (!target) {
       // If no local target has been found, find it in the global scope.
       cmTarget* const globalTarget =
-        helper.Makefile->GetGlobalGenerator()->FindTarget(
-          tgt, { cm::TargetDomain::NATIVE });
+        helper.Makefile->GetGlobalGenerator()->FindTarget(tgt);
       if (globalTarget && !globalTarget->IsImported()) {
         target = globalTarget;
       }
@@ -1369,11 +1363,6 @@ bool HandleImportedRuntimeArtifactsMode(std::vector<std::string> const& args,
   }
 
   for (std::string const& tgt : targetList) {
-    if (helper.Makefile->IsAlias(tgt)) {
-      status.SetError(cmStrCat("IMPORTED_RUNTIME_ARTIFACTS given target \"",
-                               tgt, "\" which is an alias."));
-      return false;
-    }
     // Lookup this target in the current directory.
     cmTarget* target = helper.Makefile->FindTargetToUse(tgt);
     if (!target || !target->IsImported()) {

Tests/RunCMake/alias_targets/RunCMakeTest.cmake

@@ -27,6 +27,7 @@ run_cmake(target_link_options)
 run_cmake(target_precompile_headers)
 run_cmake(target_sources)
 run_cmake(export)
+run_cmake(export-alias-and-target)
 run_cmake(install-export)
 run_cmake(name-conflict)
 run_cmake(add_dependencies)

Tests/RunCMake/alias_targets/export-alias-and-target-stderr.txt

@@ -0,0 +1,2 @@
+CMake Error in CMakeLists\.txt:
+  given target "foo" more than once\.

Tests/RunCMake/alias_targets/export-alias-and-target.cmake

@@ -0,0 +1,8 @@
+
+enable_language(CXX)
+
+add_library(foo empty.cpp)
+
+add_library(alias ALIAS foo)
+
+export(TARGETS foo alias FILE anotherFile.cmake)

Tests/RunCMake/alias_targets/export-check.cmake

@@ -0,0 +1,9 @@
+file(READ "${RunCMake_TEST_BINARY_DIR}/someFile.cmake" content)
+
+if(NOT "${content}" MATCHES "add_library\\(foo ")
+  set(RunCMake_TEST_FAILED "export(): Exported file does not define aliased target 'foo'.\n")
+endif()
+
+if("${content}" MATCHES "add_library\\(alias ")
+  set(RunCMake_TEST_FAILED "export(): Exported file lists 'alias' instead of the aliased target 'foo'.\n")
+endif()

Tests/RunCMake/alias_targets/export-stderr.txt

@@ -1,4 +0,0 @@
-CMake Error at export\.cmake:8 \(export\):
-  export given ALIAS target "alias" which may not be exported\.
-Call Stack \(most recent call first\):
-  CMakeLists\.txt:3 \(include\)

Tests/RunCMake/alias_targets/install-export-check.cmake

@@ -0,0 +1,10 @@
+string(MD5 _hash "lib/cmake")
+file(READ "${RunCMake_TEST_BINARY_DIR}/CMakeFiles/Export/${_hash}/theTargets.cmake" content)
+
+if(NOT "${content}" MATCHES "add_library\\(foo ")
+  set(RunCMake_TEST_FAILED "install(): Aliased target 'foo' was not registered in the export set.\n")
+endif()
+
+if("${content}" MATCHES "add_library\\(alias ")
+  set(RunCMake_TEST_FAILED "install(): 'alias' was registered in the export set instead of the aliased target 'foo'.\n")
+endif()

Tests/RunCMake/alias_targets/install-export-result.txt

@@ -1 +0,0 @@
-1

Tests/RunCMake/alias_targets/install-export-stderr.txt

@@ -1,4 +0,0 @@
-CMake Error at install-export\.cmake:8 \(install\):
-  install TARGETS given target "alias" which is an alias\.
-Call Stack \(most recent call first\):
-  CMakeLists\.txt:3 \(include\)