Strange problem when using qt_add_qml_module in module being brought in via FetchContent

Rich v

Going thru a CMake restructure. As part of this many internal dependencies, some of which are QML modules, are being brought in via FetchContent. With Qt6, these QML modules use qt_add_qml_module(). These modules had no issues configuring and building prior to being added thru FetchContent, but now give a CMake configuration warning as shown below:

CMake Warning at C:/Qt/6.2.4/install-dtop32-deb-and-rel/lib/cmake/Qt6Qml/Qt6QmlMacros.cmake:698 (message):
  The BCControls target is a QML module with target path BCControls.  It uses
  an OUTPUT_DIRECTORY of
  C:/Projects/build-AEPP-Desktop_Qt_6_2_4_MSVC2019_32bit-Release/_deps/bccontrols-build,
  which should end in the same target path, but doesn't.  Tooling such as
  qmllint may not work correctly.
Call Stack (most recent call first):
  C:/Qt/6.2.4/install-dtop32-deb-and-rel/lib/cmake/Qt6Qml/Qt6QmlMacros.cmake:1458 (_qt_internal_target_enable_qmllint)
  C:/Qt/6.2.4/install-dtop32-deb-and-rel/lib/cmake/Qt6Qml/Qt6QmlMacros.cmake:564 (qt6_target_qml_sources)
  C:/Qt/6.2.4/install-dtop32-deb-and-rel/lib/cmake/Qt6Qml/Qt6QmlMacros.cmake:615 (qt6_add_qml_module)
  eSW/Qt/QtCommon/BCControls/CMakeLists.txt:282 (qt_add_qml_module)

In addition, the application that is Fetching dependencies with this warning exhibits a CMake configuration error. In this example BatchExecutor, the executable wanting to link against BCControls, is complaining about a non-existent Qt6::Svg, but BatchExecutor is not itself dependent on that component. Prior to bringing BCControls in using FetchContent, there was no error.

BatchExecutor error:

CMake Error at C:/Qt/6.2.4/install-dtop32-deb-and-rel/lib/cmake/Qt6Core/Qt6CoreMacros.cmake:592 (get_target_property):
  get_target_property() called with non-existent target "Qt6::Svg".
Call Stack (most recent call first):
  C:/Qt/6.2.4/install-dtop32-deb-and-rel/lib/cmake/Qt6Core/Qt6CoreMacros.cmake:681 (_qt_internal_finalize_executable)
  C:/Qt/6.2.4/install-dtop32-deb-and-rel/lib/cmake/Qt6Core/Qt6CoreMacros.cmake:661:EVAL:1 (qt6_finalize_target)
  eSW/Qt/Apps/BatchExecutor/CMakeLists.txt:DEFERRED

This error goes away if I add Qt6::Svg on the list of REQUIRED COMPONENTS in the find_package() call.

I’m pasting the relevant sections of the CMakeLists.txt from BCControls followed by that from BatchExecutor. I realize this is as much a Qt CMake integration problem as it is a pure CMake problem, but I know gurus like Craig Scott are here often and he is a domain expert in both as well as being the author of FetchContent, IIRC.

BCControls/CMakeLists.txt (qml module):

project(BCControls)
find_package(Qt${QT_VERSION_MAJOR} COMPONENTS Core Svg Qml LinguistTools REQUIRED)

set(QML_FILES
    BCInfoScreen.qml
    # omitting many files here
   )   
set(RESOURCE_FILES 
    # omitting
)
qt_add_library(BCControls STATIC)
file(GLOB TS_FILES translations/*.ts)
qt_add_translations(BCControls
    TS_FILES ${TS_FILES}
    QM_FILES_OUTPUT_VARIABLE qmfiles
    )
qt_add_qml_module(BCControls
    URI "BCControls"
    VERSION 1.0
    QML_FILES ${QML_FILES}
    RESOURCES ${RESOURCE_FILES}
    )
qt_add_resources(BCControls "BCControlsTranslations" PREFIX "/translations" FILES ${qmfiles})

# Images in SVG format exist in bccontrols.qrc.  Need to
# load Qt${QT_VERSION_MAJOR}::Svg shared library at runtime.
target_link_libraries(BCControls
    PRIVATE
    Qt${QT_VERSION_MAJOR}::Svg
    Qt${QT_VERSION_MAJOR}::Qml
    )

BatchExecutor/CMakeLists.txt (app):

find_package(Qt${QT_VERSION_MAJOR} COMPONENTS Core Gui Qml REQUIRED)

set(RESOURCE_FILES
    # omitting
)
set(QML_FILES
    # omitting many files here
   )   
set(CPP_FILES 
    # omitting
)
qt_add_executable(BatchExecutor  ${CPP_FILES})
qt_add_qml_module(BatchExecutor
    VERSION 1.0
    URI "BatchExecutor"
    QML_FILES ${QML_FILES}
    RESOURCES ${RESOURCE_FILES}
)


FetchContent_Declare(BCControls SOURCE_DIR ${BCControls_LOC})
FetchContent_MakeAvailable(BCControls)

target_include_directories(BatchExecutor PRIVATE .)