tests: Preserve empty arguments in test command lines

This will now preserve empty values in the TEST_LAUNCHER and
CROSSCOMPILING_EMULATOR target properties for tests added by:

- The add_test() command.
- The ExternalData_Add_Test() command from the ExternalData module.
- The gtest_add_tests() or gtest_discover_tests() commands from the
  GoogleTest module.

For the gtest_add_tests() and gtest_discover_tests() commands,
empty elements in the values passed after the EXTRA_ARGS keyword
are also now preserved.

Policy CMP0178 is added to provide backward compatibility with the
old behavior where empty values were silently discarded from the
above cases.

Fixes: #26337

1 files changed, 19 insertions, 0 deletions

diff --git a/Help/release/dev/preserve-empty-args-test-command-lines.rst b/Help/release/dev/preserve-empty-args-test-command-lines.rst
new file mode 100644
index 0000000..a533ac8
--- /dev/null
+++ b/Help/release/dev/preserve-empty-args-test-command-lines.rst
@@ -0,0 +1,19 @@
+preserve-empty-args-test-command-lines
+--------------------------------------
+
+* Empty list elements in the :prop_tgt:`TEST_LAUNCHER` and
+  :prop_tgt:`CROSSCOMPILING_EMULATOR` target properties are now preserved
+  when the executable for a command given to :command:`add_test` is a CMake
+  target. See policy :policy:`CMP0178`.
+
+* Empty list elements in the :prop_tgt:`TEST_LAUNCHER` and
+  :prop_tgt:`CROSSCOMPILING_EMULATOR` target properties are now preserved
+  for the test created by :command:`ExternalData_Add_Test` from the
+  :module:`ExternalData` module.  See policy :policy:`CMP0178`.
+
+* Empty list elements in the :prop_tgt:`TEST_LAUNCHER` and
+  :prop_tgt:`CROSSCOMPILING_EMULATOR` target properties are now preserved
+  for tests created by :command:`gtest_add_tests` and
+  :command:`gtest_discover_tests` from the :module:`GoogleTest` module.
+  Empty list elements after the ``EXTRA_ARGS`` keyword of these two commands
+  are also now preserved.  See policy :policy:`CMP0178`.