add_test: Honor CROSSCOMPILING_EMULATOR only when cross-compiling

Add policy CMP0158 to provide compatibility for existing projects.

Fixes: #23672

4 files changed, 38 insertions, 0 deletions

diff --git a/Help/command/add_test.rst b/Help/command/add_test.rst
index 37b9563..557c858 100644
--- a/Help/command/add_test.rst
+++ b/Help/command/add_test.rst
@@ -42,6 +42,12 @@ directory the test is created in.
 
         <emulator> <command>
 
+      .. versionchanged:: 3.29
+
+        The emulator is used only when
+        :variable:`cross-compiling <CMAKE_CROSSCOMPILING>`.
+        See policy :policy:`CMP0158`.
+
   * .. versionadded:: 3.29
 
       The target's :prop_tgt:`TEST_LAUNCHER`, if set, will be
diff --git a/Help/manual/cmake-policies.7.rst b/Help/manual/cmake-policies.7.rst
index ddde877..35b4497 100644
--- a/Help/manual/cmake-policies.7.rst
+++ b/Help/manual/cmake-policies.7.rst
@@ -57,6 +57,7 @@ Policies Introduced by CMake 3.29
 .. toctree::
    :maxdepth: 1
 
+   CMP0158: add_test() honors CMAKE_CROSSCOMPILING_EMULATOR only when cross-compiling. </policy/CMP0158>
    CMP0157: Swift compilation mode is selected by an abstraction. </policy/CMP0157>
    CMP0156: De-duplicate libraries on link lines based on linker capabilities. </policy/CMP0156>
 
diff --git a/Help/policy/CMP0158.rst b/Help/policy/CMP0158.rst
new file mode 100644
index 0000000..4289c6d
--- /dev/null
+++ b/Help/policy/CMP0158.rst
@@ -0,0 +1,27 @@
+CMP0158
+-------
+
+.. versionadded:: 3.29
+
+:command:`add_test` honors :variable:`CMAKE_CROSSCOMPILING_EMULATOR` only
+when :variable:`cross-compiling <CMAKE_CROSSCOMPILING>`.
+
+In CMake 3.28 and below, :command:`add_test` unconditionally used the
+:prop_tgt:`CROSSCOMPILING_EMULATOR` target property (initialized by the
+:variable:`CMAKE_CROSSCOMPILING_EMULATOR` variable) to run test commands
+naming executable targets.  CMake 3.29 and above prefer to use the emulator
+only when the :variable:`CMAKE_CROSSCOMPILING` variable is enabled.  The
+:variable:`CMAKE_TEST_LAUNCHER` variable may be used instead when not
+cross-compiling.  This policy provides compatibility for projects that
+have not been updated.
+
+The ``OLD`` behavior for this policy is for :command:`add_test` to use
+the :prop_tgt:`CROSSCOMPILING_EMULATOR` target property unconditionally.
+The ``NEW`` behavior for this policy is for :command:`add_test` to use
+the :prop_tgt:`CROSSCOMPILING_EMULATOR` target property only when
+:variable:`cross-compiling <CMAKE_CROSSCOMPILING>`.
+
+This policy was introduced in CMake version 3.29. Use the
+:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
+Unlike many policies, CMake version |release| does *not* warn
+when this policy is not set and simply uses ``OLD`` behavior.
diff --git a/Help/release/dev/cmake-test-launcher.rst b/Help/release/dev/cmake-test-launcher.rst
index e97498d..a82a8ad 100644
--- a/Help/release/dev/cmake-test-launcher.rst
+++ b/Help/release/dev/cmake-test-launcher.rst
@@ -5,3 +5,7 @@ cmake-test-launcher
   :prop_tgt:`TEST_LAUNCHER` target property were added to specify
   a launcher to be used by executable targets when invoked by
   tests added by the :command:`add_test` command.
+
+* The :command:`add_test` command now honors
+  :variable:`CMAKE_CROSSCOMPILING_EMULATOR` only when cross-compiling.
+  See policy :policy:`CMP0158`.