CMake: Allow excluding tools and apps from the default 'all' target

Qt uses the qtNomakeTools() function to mark a directory which will
not be built as part of the default target. This is especially
important when cross-compiling (to iOS for example) because the build
process might fail.

The condition for not building these "GUI tool sub-directory projects"
is the absence of the "tools" value in qmake's QT_BUILD_PARTS
variable.

Introduce a QT_NO_MAKE_TOOLS CMake variable. If the value is true,
it's equivalent to "tools" not being present in QT_BUILD_PARTS.

Introduce qt_exclude_tool_directories_from_default_target().
It's the qmake counter part to qtNomakeTools().

Teach pro2cmake to generate it where appropriate.

Change-Id: If2e5958d91847ab139af0e452608510286e73fa0
Reviewed-by: Leander Beernaert <leander.beernaert@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

cmake/QtBuild.cmake

@@ -4124,6 +4124,29 @@ function(qt_enable_msvc_cplusplus_define target visibility)
     endif()
 endfunction()
 
+# Equivalent of qmake's qtNomakeTools(directory1 directory2).
+# If QT_NO_MAKE_TOOLS is true, then the given directories will be excluded from the
+# default 'all' target.
+function(qt_exclude_tool_directories_from_default_target)
+    if(QT_NO_MAKE_TOOLS)
+        set(absolute_path_directories "")
+        foreach(directory ${ARGV})
+            list(APPEND absolute_path_directories "${CMAKE_CURRENT_SOURCE_DIR}/${directory}")
+        endforeach()
+
+        # Properties can only be set on processed directories (some might not be processed due to
+        # disabled features). So we need to exclude only processed directories.
+        get_directory_property(subdirectories SUBDIRECTORIES)
+
+        # Poor man's set intersection.
+        foreach(directory ${absolute_path_directories})
+            if(directory IN_LIST subdirectories)
+                set_property(DIRECTORY "${directory}" PROPERTY EXCLUDE_FROM_ALL TRUE)
+            endif()
+        endforeach()
+    endif()
+endfunction()
+
 # Compatibility macros that should be removed once all their usages are removed.
 function(extend_target)
     qt_extend_target(${ARGV})

cmake/QtSetup.cmake

@@ -122,6 +122,12 @@ if(QT_BUILD_STANDALONE_TESTS)
 endif()
 option(QT_NO_MAKE_TESTS "Should tests be built as part of the default 'all' target." OFF)
 
+# When cross-building, we don't build tools by default. Sometimes this also covers Qt apps as well.
+# Like in qttools/assistant/assistant.pro, load(qt_app), which is guarded by a qtNomakeTools() call.
+
+option(QT_NO_MAKE_TOOLS "Should tools be built as part of the default 'all' target."
+       "${CMAKE_CROSSCOMPILING}")
+
 include(CTest)
 enable_testing()
 

util/cmake/pro2cmake.py

@@ -1064,6 +1064,13 @@ class Scope(object):
             if project_required_condition:
                 scope._append_operation("_REQUIREMENTS", AddOperation(project_required_condition))
 
+            qt_no_make_tools = statement.get("qt_no_make_tools_arguments")
+            if qt_no_make_tools:
+                qt_no_make_tools = qt_no_make_tools.strip("()").strip()
+                qt_no_make_tools = qt_no_make_tools.split()
+                for entry in qt_no_make_tools:
+                    scope._append_operation("_QT_NO_MAKE_TOOLS", AddOperation(entry))
+
         scope.settle_condition()
 
         if scope.scope_debug:
@@ -1783,6 +1790,16 @@ def handle_subdir(
     )
     group_and_print_sub_dirs(scope, indent=indent)
 
+    qt_no_make_tools = scope.get("_QT_NO_MAKE_TOOLS")
+    if qt_no_make_tools:
+        ind = spaces(indent + 1)
+        directories_string = ""
+        for directory in qt_no_make_tools:
+            directories_string += f"{ind}{directory}\n"
+        cm_fh.write(
+            f"\nqt_exclude_tool_directories_from_default_target(\n{directories_string})\n\n"
+        )
+
 
 def sort_sources(sources: List[str]) -> List[str]:
     to_sort = {}  # type: Dict[str, List[str]]

util/cmake/qmake_parser.py

@@ -243,6 +243,14 @@ class QmakeParser:
             "Requires", pp.Keyword("requires") + RequiresCondition("project_required_condition")
         )
 
+        FunctionArgumentsAsString = add_element(
+            "FunctionArgumentsAsString", pp.originalTextFor(pp.nestedExpr())
+        )
+        QtNoMakeTools = add_element(
+            "QtNoMakeTools",
+            pp.Keyword("qtNomakeTools") + FunctionArgumentsAsString("qt_no_make_tools_arguments"),
+        )
+
         # ignore the whole thing...
         DefineTestDefinition = add_element(
             "DefineTestDefinition",
@@ -281,6 +289,7 @@ class QmakeParser:
                 | Include
                 | Option
                 | Requires
+                | QtNoMakeTools
                 | ForLoop
                 | ForLoopSingleLine
                 | DefineTestDefinition