CMake: Disable static plugin imports for non-executable targets

There is no point in generating cpp files containing Q_IMPORT_PLUGIN()
macro calls for non-executable targets like modules, plugins and object
libraries in a static Qt build.
It causes unnecessary compiling of 10+ files for each of those targets.
In a static Qt build, plugin imports should only be done for executables,
tools and applications.

Pick-to: 6.0
Change-Id: Ied90ef2f6d77a61a093d393cfdf94c400284c4f0
Reviewed-by: Craig Scott <craig.scott@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

cmake/Qt3rdPartyLibraryHelpers.cmake

@@ -9,11 +9,14 @@ function(qt_internal_add_cmake_library target)
         ${ARGN}
     )
 
+    set(is_static_lib 0)
+
     ### Define Targets:
     if(${arg_INTERFACE})
         add_library("${target}" INTERFACE)
     elseif(${arg_STATIC} OR (${arg_MODULE} AND NOT BUILD_SHARED_LIBS))
         add_library("${target}" STATIC)
+        set(is_static_lib 1)
     elseif(${arg_SHARED})
         add_library("${target}" SHARED)
         qt_internal_apply_win_prefix_and_suffix("${target}")
@@ -32,6 +35,9 @@ function(qt_internal_add_cmake_library target)
         qt_internal_apply_win_prefix_and_suffix("${target}")
     else()
         add_library("${target}")
+        if(NOT BUILD_SHARED_LIBS)
+            set(is_static_lib 1)
+        endif()
     endif()
 
     if (NOT arg_ARCHIVE_INSTALL_DIRECTORY AND arg_INSTALL_DIRECTORY)
@@ -43,6 +49,11 @@ function(qt_internal_add_cmake_library target)
     endif()
     qt_skip_warnings_are_errors_when_repo_unclean("${target}")
 
+    # No need to compile Q_IMPORT_PLUGIN-containing files for non-executables.
+    if(is_static_lib)
+        _qt_internal_disable_static_default_plugins("${target}")
+    endif()
+
     if (arg_INSTALL_DIRECTORY)
         set(install_arguments
             ARCHIVE_INSTALL_DIRECTORY ${arg_ARCHIVE_INSTALL_DIRECTORY}
@@ -93,11 +104,14 @@ function(qt_internal_add_3rdparty_library target)
         ${ARGN}
     )
 
+    set(is_static_lib 0)
+
     ### Define Targets:
     if(${arg_INTERFACE})
         add_library("${target}" INTERFACE)
     elseif(${arg_STATIC} OR (${arg_MODULE} AND NOT BUILD_SHARED_LIBS))
         add_library("${target}" STATIC)
+        set(is_static_lib 1)
     elseif(${arg_SHARED})
         add_library("${target}" SHARED)
     elseif(${arg_MODULE})
@@ -114,6 +128,9 @@ function(qt_internal_add_3rdparty_library target)
         endif()
     else()
         add_library("${target}")
+        if(NOT BUILD_SHARED_LIBS)
+            set(is_static_lib 1)
+        endif()
     endif()
 
     if(NOT arg_INTERFACE)
@@ -128,6 +145,11 @@ function(qt_internal_add_3rdparty_library target)
     qt_internal_add_target_aliases(${target})
     _qt_internal_apply_strict_cpp(${target})
 
+    # No need to compile Q_IMPORT_PLUGIN-containing files for non-executables.
+    if(is_static_lib)
+        _qt_internal_disable_static_default_plugins("${target}")
+    endif()
+
     if (ANDROID)
         qt_android_apply_arch_suffix("${target}")
     endif()

cmake/QtModuleHelpers.cmake

@@ -31,16 +31,19 @@ function(qt_internal_add_module target)
     ### Define Targets:
     set(is_interface_lib 0)
     set(is_shared_lib 0)
+    set(is_static_lib 0)
     if(${arg_HEADER_MODULE})
         add_library("${target}" INTERFACE)
         set(is_interface_lib 1)
     elseif(${arg_STATIC})
         add_library("${target}" STATIC)
+        set(is_static_lib 1)
     elseif(${QT_BUILD_SHARED_LIBS})
         add_library("${target}" SHARED)
         set(is_shared_lib 1)
     else()
         add_library("${target}" STATIC)
+        set(is_static_lib 1)
     endif()
 
     set(property_prefix "INTERFACE_")
@@ -86,6 +89,11 @@ function(qt_internal_add_module target)
     qt_skip_warnings_are_errors_when_repo_unclean("${target}")
     _qt_internal_apply_strict_cpp("${target}")
 
+    # No need to compile Q_IMPORT_PLUGIN-containing files for non-executables.
+    if(is_static_lib)
+        _qt_internal_disable_static_default_plugins("${target}")
+    endif()
+
     # Add _private target to link against the private headers:
     if(NOT ${arg_NO_PRIVATE_MODULE})
         set(target_private "${target}Private")

cmake/QtPluginHelpers.cmake

@@ -88,7 +88,7 @@ function(qt_internal_add_plugin target)
 
     # Disable linking of plugins against other plugins during static regular and
     # super builds. The latter causes cyclic dependencies otherwise.
-    set_target_properties(${target} PROPERTIES QT_DEFAULT_PLUGINS 0)
+    _qt_internal_disable_static_default_plugins("${target}")
 
     set_target_properties("${target}" PROPERTIES
         LIBRARY_OUTPUT_DIRECTORY "${output_directory}"

src/corelib/Qt6CoreMacros.cmake

@@ -494,6 +494,10 @@ macro(_qt_import_plugin target plugin)
     endif()
 endmacro()
 
+function(_qt_internal_disable_static_default_plugins target)
+    set_target_properties(${target} PROPERTIES QT_DEFAULT_PLUGINS 0)
+endfunction()
+
 # This function is used to indicate which plug-ins are going to be
 # used by a given target.
 # This allows static linking to a correct set of plugins.
@@ -518,7 +522,7 @@ function(qt6_import_plugins target)
 
     # Handle NO_DEFAULT
     if(${arg_NO_DEFAULT})
-        set_target_properties(${target} PROPERTIES QT_DEFAULT_PLUGINS 0)
+        _qt_internal_disable_static_default_plugins("${target}")
     endif()
 
     # Handle INCLUDE
@@ -1088,6 +1092,9 @@ function(__qt_propagate_generated_resource target resource_name generated_source
         target_link_libraries(${target} INTERFACE
                               "$<TARGET_OBJECTS:$<TARGET_NAME:${resource_target}>>")
         set(${output_generated_target} "${resource_target}" PARENT_SCOPE)
+
+        # No need to compile Q_IMPORT_PLUGIN-containing files for non-executables.
+        _qt_internal_disable_static_default_plugins("${resource_target}")
     else()
         set(${output_generated_target} "" PARENT_SCOPE)
         target_sources(${target} PRIVATE ${generated_source_code})