CPack/DMG: Add explicit option to use CPACK_RESOURCE_FILE_LICENSE for SLA

Since macOS 12.0, the ``hdiutil udifrez`` and ``hdiutil udifderez``
commands to embed and extract resources in a disk image are deprecated.
The CPack DragNDrop Generator uses these to attach the SLA specified by
the `CPACK_RESOURCE_FILE_LICENSE` option.  Since that option is shared
by multiple CPack generators, we cannot deprecate it.  Instead, add an
explicit option to control the behavior.  This will give projects a way
to package on future macOS versions that remove the commands.

In order to provide a long-term transition away from attaching SLAs to
disk images, update `cpack` to default this behavior to OFF.  To retain
compatibility for CMake projects, teach the CPack module to default the
option to ON.  Later a policy can be added to change the default.

Issue: #22978

Help/cpack_gen/dmg.rst

@@ -54,6 +54,27 @@ on macOS:
  Default behavior is to include a symlink to ``/Applications`` in the DMG.
  Set this option to ``ON`` to avoid adding the symlink.
 
+.. variable:: CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE
+
+ .. versionadded:: 3.23
+
+ Control whether :variable:`CPACK_RESOURCE_FILE_LICENSE`, if set to a
+ non-default value, is used as the license agreement provided when
+ mounting the DMG.  If ``CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE`` is
+ not set, :manual:`cpack(1)` defaults to off.
+
+ In a CMake project that uses the :module:`CPack` module to generate
+ ``CPackConfig.cmake``, ``CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE``
+ is automatically enabled by default if it is not set and
+ :variable:`CPACK_RESOURCE_FILE_LICENSE` is set to a non-default value.
+
+ .. note::
+
+  This option was added in response to macOS 12.0's deprecation of
+  the ``hdiutil udifrez`` command to make its use optional.
+  CPack 3.22 and below always use :variable:`CPACK_RESOURCE_FILE_LICENSE`,
+  if set to a non-default value, as the DMG license.
+
 .. variable:: CPACK_DMG_SLA_DIR
 
   .. versionadded:: 3.5

Help/release/dev/cpack-dmg-sla.rst

@@ -0,0 +1,9 @@
+cpack-dmg-sla
+-------------
+
+* The :cpack_gen:`CPack DragNDrop Generator` no longer attaches
+  :variable:`CPACK_RESOURCE_FILE_LICENSE` as the license agreement in
+  the generated ``.dmg`` unless explicitly activated by a
+  :variable:`CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE` option.
+  In CMake projects, the :module:`CPack` module enables the option
+  by default for compatibility.

Modules/CPack.cmake

@@ -805,6 +805,11 @@ _cpack_set_default(CPACK_INSTALL_PREFIX "${CMAKE_INSTALL_PREFIX}")
 _cpack_set_default(CPACK_NSIS_INSTALLER_ICON_CODE "")
 _cpack_set_default(CPACK_NSIS_INSTALLER_MUI_ICON_CODE "")
 
+# DragNDrop specific variables
+if(CPACK_RESOURCE_FILE_LICENSE AND NOT CPACK_RESOURCE_FILE_LICENSE STREQUAL "${CMAKE_ROOT}/Templates/CPack.GenericLicense.txt")
+  _cpack_set_default(CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE ON)
+endif()
+
 # WiX specific variables
 _cpack_set_default(CPACK_WIX_SIZEOF_VOID_P "${CMAKE_SIZEOF_VOID_P}")
 

Source/CPack/cmCPackDragNDropGenerator.cxx

@@ -98,7 +98,9 @@ int cmCPackDragNDropGenerator::InitializeInternal()
 
   if (this->IsSet("CPACK_DMG_SLA_DIR")) {
     slaDirectory = this->GetOption("CPACK_DMG_SLA_DIR");
-    if (!slaDirectory.empty() && this->IsSet("CPACK_RESOURCE_FILE_LICENSE")) {
+    if (!slaDirectory.empty() &&
+        this->IsOn("CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE") &&
+        this->IsSet("CPACK_RESOURCE_FILE_LICENSE")) {
       std::string license_file =
         this->GetOption("CPACK_RESOURCE_FILE_LICENSE");
       if (!license_file.empty() &&
@@ -278,8 +280,10 @@ int cmCPackDragNDropGenerator::CreateDMG(const std::string& src_dir,
     : "HFS+";
 
   // Get optional arguments ...
-  std::string cpack_license_file =
-    *this->GetOption("CPACK_RESOURCE_FILE_LICENSE");
+  std::string cpack_license_file;
+  if (this->IsOn("CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE")) {
+    cpack_license_file = *this->GetOption("CPACK_RESOURCE_FILE_LICENSE");
+  }
 
   cmValue cpack_dmg_background_image =
     this->GetOption("CPACK_DMG_BACKGROUND_IMAGE");

Tests/RunCMake/CPack/RunCMakeTest.cmake

@@ -22,6 +22,7 @@ endif()
 run_cpack_test(DIST "RPM.DIST" false "MONOLITHIC")
 run_cpack_test(DMG_SLA "DragNDrop" false "MONOLITHIC")
 run_cpack_test(DMG_SLA_FILE "DragNDrop" false "MONOLITHIC")
+run_cpack_test(DMG_SLA_OFF "DragNDrop" false "MONOLITHIC")
 run_cpack_test(EMPTY_DIR "RPM.EMPTY_DIR;DEB.EMPTY_DIR;TGZ" true "MONOLITHIC;COMPONENT")
 run_cpack_test(VERSION "RPM.VERSION;DEB.VERSION" false "MONOLITHIC;COMPONENT")
 run_cpack_test(EXTRA "DEB.EXTRA" false "COMPONENT")

Tests/RunCMake/CPack/tests/DMG_SLA_OFF/Example.txt

@@ -0,0 +1,4 @@
+Example License File
+--------------------
+
+This is an example license file for a DMG.

Tests/RunCMake/CPack/tests/DMG_SLA_OFF/ExpectedFiles.cmake

@@ -0,0 +1,2 @@
+set(EXPECTED_FILES_COUNT "1")
+set(EXPECTED_FILE_CONTENT_1_LIST "/foo;/foo/CMakeLists.txt")

Tests/RunCMake/CPack/tests/DMG_SLA_OFF/VerifyResult.cmake

@@ -0,0 +1,12 @@
+set(dmg "${bin_dir}/${FOUND_FILE_1}")
+execute_process(COMMAND hdiutil udifderez -xml "${dmg}" OUTPUT_VARIABLE out ERROR_VARIABLE err RESULT_VARIABLE res)
+if(NOT res EQUAL 0)
+  string(REPLACE "\n" "\n  " err "  ${err}")
+  message(FATAL_ERROR "Running 'hdiutil udifderez -xml' on\n  ${dmg}\nfailed with:\n${err}")
+endif()
+foreach(key "LPic" "STR#" "TEXT")
+  if(out MATCHES "<key>${key}</key>")
+    string(REPLACE "\n" "\n  " out "  ${out}")
+    message(FATAL_ERROR "error: running 'hdiutil udifderez -xml' on\n  ${dmg}\nhas unexpected '${key}' key:\n${out}")
+  endif()
+endforeach()

Tests/RunCMake/CPack/tests/DMG_SLA_OFF/test.cmake

@@ -0,0 +1,3 @@
+install(FILES CMakeLists.txt DESTINATION foo)
+set(CPACK_RESOURCE_FILE_LICENSE "${CMAKE_CURRENT_LIST_DIR}/Example.txt")
+set(CPACK_DMG_SLA_USE_RESOURCE_FILE_LICENSE OFF)