CMake: Mark qm files as GENERATED in the target scope

Projects with cmake_minimum_required(VERSION 3.19) or below, so with
no support for the CMP0118 policy, failed to configure when
translations were added in a subdirectory scope different from
the target scope.

qt_add_translations adds qm files to resources, that in turn calls
_qt_internal_expose_deferred_files_to_ide which adds the qm files
to the target sources.

Because qm files are created using add_custom_command, which by default
marks the files as GENERATED only in the directory scope of the
command (unless CMP0118 is set to NEW), that causes add_executable to
think the qm files are not generated, and error out with
"Cannot find source file:".

Explicitly set the GENERATED flag in the target directory scope to
avoid the issue when using CMake 3.18+.

The error still happens with CMake 3.17 or lower, but that's not the
only error that happens. Just adding resources in a different
subdirectory without exposing the source files already fails, and
that's not something we can really fix without a newer CMake version.

Pick-to: 6.5
Fixes: QTBUG-112841
Change-Id: I79eced94ac641a6f9239f3eb721cef5e35f847fa
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>
Reviewed-by: Amir Masoud Abdol <amir.abdol@qt.io>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/linguist/Qt6LinguistToolsMacros.cmake b/src/linguist/Qt6LinguistToolsMacros.cmake
index 637202267..c992bfa41 100644
--- a/src/linguist/Qt6LinguistToolsMacros.cmake
+++ b/src/linguist/Qt6LinguistToolsMacros.cmake
@@ -246,6 +246,21 @@ function(qt6_add_lrelease target)
             ${lrelease_command} ${arg_OPTIONS} ${ts_file} -qm ${qm}
             DEPENDS ${QT_CMAKE_EXPORT_NAMESPACE}::lrelease "${ts_file}"
             VERBATIM)
+
+        # Mark file as GENERATED, so that calling _qt_internal_expose_deferred_files_to_ide
+        # doesn't cause an error at generation time saying "Cannot find source file:" when
+        # qt6_add_lrelease is called from a subdirectory different than the target.
+        # The issue happend when the user project called cmake_minimum_required(VERSION)
+        # with a version less than 3.20 or set the CMP0118 policy value to OLD.
+        set(scope_args)
+        if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.18")
+            set(scope_args TARGET_DIRECTORY ${target})
+        endif()
+        set_source_files_properties(${qm}
+            ${scope_args}
+            PROPERTIES GENERATED TRUE
+        )
+
         list(APPEND qm_files "${qm}")
 
         # QTBUG-103470: Save the target responsible for driving the build of the custom command