Simplify resource embedding for qml modules

* Add support for a QT_RESOURCE_PREFIX target property, that
      add_qt_resource respects. This makes it convenient to add files
      to the resource system for a project without the need to repeat
      prefixes. In qmake land with multiple resources they're repeated
      in the foo.prefix variables or in the prefix attribute in .qrc
      files.

    * Since /qt-project.org/imports is in the default QML import search path
       and the hierarchy under the import search paths is "regulated",
       we might as well make add_qml_module set QT_RESOURCE_PREFIX on
       the target. We can compute the correct value for that. This
       allows removing the redundant prefix from the add_qt_resource()
       calls for the qml files.

Change-Id: Ic15130dc9e432340fc3edf93e35f2a803b4b40eb
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Reviewed-by: Qt CMake Build Bot

cmake/QtBuild.cmake

@@ -1905,8 +1905,6 @@ endfunction()
 #  to the module's URI where '.' is replaced with '/'. Use this to override the
 #  default substitution pattern.
 #  VERSION: Version of the qml module
-#  RESOURCE_PREFIX: Resource import prefix to be prepended to the module's
-#  target path.
 #  QML_PLUGINDUMP_DEPENDENCIES: Path to a dependencies.json file to be consumed
 #  with the ${target}_qmltypes target (optional)
 #
@@ -1920,7 +1918,6 @@ function(add_qml_module target)
         URI
         TARGET_PATH
         VERSION
-        RESOURCE_PREFIX
         QML_PLUGINDUMP_DEPENDENCIES
     )
 
@@ -1939,10 +1936,6 @@ function(add_qml_module target)
         message(FATAL_ERROR "add_qml_module called without specifying the module's import version. Please specify one using the VERSION parameter.")
     endif()
 
-    if (NOT arg_RESOURCE_PREFIX)
-        message(FATAL_ERROR "add_qml_module called without specifying the module's import prefix. Prease specify one using the RESOURCE_PREFIX parameter.")
-    endif()
-
     if (NOT arg_TARGET_PATH)
         string(REPLACE "." "/" arg_TARGET_PATH ${arg_URI})
     endif()
@@ -1983,7 +1976,7 @@ function(add_qml_module target)
         PROPERTIES
             QT_QML_MODULE_TARGET_PATH ${arg_TARGET_PATH}
             QT_QML_MODULE_URI ${arg_URI}
-            QT_QML_MODULE_RESOURCE_PREFIX ${arg_RESOURCE_PREFIX}
+            QT_RESOURCE_PREFIX "/qt-project.org/imports/${arg_TARGET_PATH}"
             QT_QML_MODULE_VERSION ${arg_VERSION}
     )
 
@@ -2017,7 +2010,6 @@ function(add_qml_module target)
         set(qmldir_resource_name "${qmldir_resource_name}_qmldir")
         add_qt_resource(${target} ${uri_target}
             FILES "${CMAKE_CURRENT_SOURCE_DIR}/qmldir"
-            PREFIX "${arg_RESOURCE_PREFIX}/${arg_TARGET_PATH}"
         )
     endif()
 
@@ -2547,6 +2539,9 @@ function(add_qt_resource target resourceName)
         set(resource_files ${rcc_FILES})
     endif()
 
+    if(NOT rcc_PREFIX)
+        get_target_property(rcc_PREFIX ${target} QT_RESOURCE_PREFIX)
+    endif()
 
     # Apply quick compiler pass
     qt_quick_compiler_process_resources(${target} ${resourceName}

cmake/QtProperties.cmake

@@ -79,11 +79,12 @@ define_property(TARGET
 
 define_property(TARGET
     PROPERTY
-        QT_QML_MODULE_RESOURCE_PREFIX
+        QT_RESOURCE_PREFIX
     BRIEF_DOCS
-        "Specifies the qml module's resource prefix."
+        "Specifies the default Qt resource prefix."
     FULL_DOCS
-        "Specifies the qml module's resource prefix."
+        "When using add_qt_resource() without a PREFIX, then prefix of this target property
+        will be used."
 )
 
 define_property(TARGET

util/cmake/pro2cmake.py

@@ -2097,8 +2097,6 @@ def write_qml_plugin(cm_fh: typing.IO[str],
     if plugindump_dep:
         extra_lines.append('QML_PLUGINDUMP_DEPENDENCIES "{}"'.format(plugindump_dep))
 
-    # This is only required because of qmldir
-    extra_lines.append('RESOURCE_PREFIX "/qt-project.org/imports"')
 
 def write_qml_plugin_qml_files(cm_fh: typing.IO[str],
                                target: str,
@@ -2116,15 +2114,11 @@ def write_qml_plugin_qml_files(cm_fh: typing.IO[str],
         target_path_mangled = target_path.replace('/', '_')
         target_path_mangled = target_path_mangled.replace('.', '_')
         resource_name = 'qmake_' + target_path_mangled
-        prefix = '/qt-project.org/imports/' + target_path
-        cm_fh.write('\n{}add_qt_resource({} {}\n{}PREFIX\n{}"{}"\n{}FILES\n{}${{qml_files}}\n)\n'.format(
+        cm_fh.write('\n{}add_qt_resource({} {}\n{}FILES\n{}${{qml_files}}\n)\n'.format(
             spaces(indent),
             target,
             resource_name,
             spaces(indent + 1),
-            spaces(indent + 2),
-            prefix,
-            spaces(indent + 1),
             spaces(indent + 2)))
 
         cm_fh.write('\nqt_install_qml_files({}\n    FILES ${{qml_files}}\n)\n\n'.format(