def _preview_module_system(request, descriptor, field_data):
    """
    Returns a ModuleSystem for the specified descriptor that is specialized for
    rendering module previews.

    request: The active django request
    descriptor: An XModuleDescriptor
    """

    course_id = descriptor.location.course_key
    display_name_only = (descriptor.category == 'static_tab')

    wrappers = [
        # This wrapper wraps the module in the template specified above
        partial(
            wrap_xblock,
            'PreviewRuntime',
            display_name_only=display_name_only,
            usage_id_serializer=unicode,
            request_token=request_token(request)
        ),

        # This wrapper replaces urls in the output that start with /static
        # with the correct course-specific url for the static content
        partial(replace_static_urls, None, course_id=course_id),
        _studio_wrap_xblock,
    ]

    descriptor.runtime._services['studio_user_permissions'] = StudioPermissionsService(request)  # pylint: disable=protected-access

    return PreviewModuleSystem(
        static_url=settings.STATIC_URL,
        # TODO (cpennington): Do we want to track how instructors are using the preview problems?
        track_function=lambda event_type, event: None,
        filestore=descriptor.runtime.resources_fs,
        get_module=partial(_load_preview_module, request),
        render_template=render_from_lms,
        debug=True,
        replace_urls=partial(static_replace.replace_static_urls, data_directory=None, course_id=course_id),
        user=request.user,
        can_execute_unsafe_code=(lambda: can_execute_unsafe_code(course_id)),
        get_python_lib_zip=(lambda: get_python_lib_zip(contentstore, course_id)),
        mixins=settings.XBLOCK_MIXINS,
        course_id=course_id,
        anonymous_student_id='student',

        # Set up functions to modify the fragment produced by student_view
        wrappers=wrappers,
        error_descriptor_class=ErrorDescriptor,
        get_user_role=lambda: get_user_role(request.user, course_id),
        # Get the raw DescriptorSystem, not the CombinedSystem
        descriptor_runtime=descriptor._runtime,  # pylint: disable=protected-access
        services={
            "i18n": ModuleI18nService(),
            "field-data": field_data,
            "library_tools": LibraryToolsService(modulestore()),
            "settings": SettingsService(),
            "user": DjangoXBlockUserService(request.user),
        },
    )

#.........这里部分代码省略.........
    # These modules store data using the anonymous_student_id as a key.
    # To prevent loss of data, we will continue to provide old modules with
    # the per-student anonymized id (as we have in the past),
    # while giving selected modules a per-course anonymized id.
    # As we have the time to manually test more modules, we can add to the list
    # of modules that get the per-course anonymized id.
    is_pure_xblock = isinstance(descriptor, XBlock) and not isinstance(descriptor, XModuleDescriptor)
    module_class = getattr(descriptor, 'module_class', None)
    is_lti_module = not is_pure_xblock and issubclass(module_class, LTIModule)
    if is_pure_xblock or is_lti_module:
        anonymous_student_id = anonymous_id_for_user(user, course_id)
    else:
        anonymous_student_id = anonymous_id_for_user(user, None)

    field_data = LmsFieldData(descriptor._field_data, student_data)  # pylint: disable=protected-access

    user_is_staff = has_access(user, u'staff', descriptor.location, course_id)

    system = LmsModuleSystem(
        track_function=track_function,
        render_template=render_to_string,
        static_url=settings.STATIC_URL,
        xqueue=xqueue,
        # TODO (cpennington): Figure out how to share info between systems
        filestore=descriptor.runtime.resources_fs,
        get_module=inner_get_module,
        user=user,
        debug=settings.DEBUG,
        hostname=settings.SITE_NAME,
        # TODO (cpennington): This should be removed when all html from
        # a module is coming through get_html and is therefore covered
        # by the replace_static_urls code below
        replace_urls=partial(
            static_replace.replace_static_urls,
            data_directory=getattr(descriptor, 'data_dir', None),
            course_id=course_id,
            static_asset_path=static_asset_path or descriptor.static_asset_path,
        ),
        replace_course_urls=partial(
            static_replace.replace_course_urls,
            course_key=course_id
        ),
        replace_jump_to_id_urls=partial(
            static_replace.replace_jump_to_id_urls,
            course_id=course_id,
            jump_to_id_base_url=reverse('jump_to_id', kwargs={'course_id': course_id.to_deprecated_string(), 'module_id': ''})
        ),
        node_path=settings.NODE_PATH,
        publish=publish,
        anonymous_student_id=anonymous_student_id,
        course_id=course_id,
        open_ended_grading_interface=open_ended_grading_interface,
        s3_interface=s3_interface,
        cache=cache,
        can_execute_unsafe_code=(lambda: can_execute_unsafe_code(course_id)),
        get_python_lib_zip=(lambda: get_python_lib_zip(contentstore, course_id)),
        # TODO: When we merge the descriptor and module systems, we can stop reaching into the mixologist (cpennington)
        mixins=descriptor.runtime.mixologist._mixins,  # pylint: disable=protected-access
        wrappers=block_wrappers,
        get_real_user=user_by_anonymous_id,
        services={
            'i18n': ModuleI18nService(),
            'fs': xblock.reference.plugins.FSService(),
            'field-data': field_data,
            'user': DjangoXBlockUserService(user, user_is_staff=user_is_staff),
        },
        get_user_role=lambda: get_user_role(user, course_id),
        descriptor_runtime=descriptor._runtime,  # pylint: disable=protected-access
        rebind_noauth_module_to_user=rebind_noauth_module_to_user,
        user_location=user_location,
        request_token=request_token,
    )

    # pass position specified in URL to module through ModuleSystem
    if position is not None:
        try:
            position = int(position)
        except (ValueError, TypeError):
            log.exception('Non-integer %r passed as position.', position)
            position = None

    system.set('position', position)
    if settings.FEATURES.get('ENABLE_PSYCHOMETRICS') and user.is_authenticated():
        system.set(
            'psychometrics_handler',  # set callback for updating PsychometricsData
            make_psychometrics_data_update_handler(course_id, user, descriptor.location)
        )

    system.set(u'user_is_staff', user_is_staff)
    system.set(u'user_is_admin', has_access(user, u'staff', 'global'))
    system.set(u'user_is_beta_tester', CourseBetaTesterRole(course_id).has_user(user))
    system.set(u'days_early_for_beta', getattr(descriptor, 'days_early_for_beta'))

    # make an ErrorDescriptor -- assuming that the descriptor's system is ok
    if has_access(user, u'staff', descriptor.location, course_id):
        system.error_descriptor_class = ErrorDescriptor
    else:
        system.error_descriptor_class = NonStaffErrorDescriptor

    return system, field_data

#.........这里部分代码省略.........
        if staff_access:
            block_wrappers.append(partial(add_staff_markup, user, instructor_access, disable_staff_debug_info))

    # These modules store data using the anonymous_student_id as a key.
    # To prevent loss of data, we will continue to provide old modules with
    # the per-student anonymized id (as we have in the past),
    # while giving selected modules a per-course anonymized id.
    # As we have the time to manually test more modules, we can add to the list
    # of modules that get the per-course anonymized id.
    is_pure_xblock = isinstance(descriptor, XBlock) and not isinstance(descriptor, XModuleDescriptor)
    module_class = getattr(descriptor, 'module_class', None)
    is_lti_module = not is_pure_xblock and issubclass(module_class, LTIModule)
    if is_pure_xblock or is_lti_module:
        anonymous_student_id = anonymous_id_for_user(user, course_id)
    else:
        anonymous_student_id = anonymous_id_for_user(user, None)

    field_data = LmsFieldData(descriptor._field_data, student_data)  # pylint: disable=protected-access

    user_is_staff = bool(has_access(user, u'staff', descriptor.location, course_id))

    system = LmsModuleSystem(
        track_function=track_function,
        render_template=render_to_string,
        static_url=settings.STATIC_URL,
        xqueue=xqueue,
        # TODO (cpennington): Figure out how to share info between systems
        filestore=descriptor.runtime.resources_fs,
        get_module=inner_get_module,
        user=user,
        debug=settings.DEBUG,
        hostname=settings.SITE_NAME,
        # TODO (cpennington): This should be removed when all html from
        # a module is coming through get_html and is therefore covered
        # by the replace_static_urls code below
        replace_urls=partial(
            static_replace.replace_static_urls,
            data_directory=getattr(descriptor, 'data_dir', None),
            course_id=course_id,
            static_asset_path=static_asset_path or descriptor.static_asset_path,
        ),
        replace_course_urls=partial(
            static_replace.replace_course_urls,
            course_key=course_id
        ),
        replace_jump_to_id_urls=partial(
            static_replace.replace_jump_to_id_urls,
            course_id=course_id,
            jump_to_id_base_url=reverse('jump_to_id', kwargs={'course_id': course_id.to_deprecated_string(), 'module_id': ''})
        ),
        node_path=settings.NODE_PATH,
        publish=publish,
        anonymous_student_id=anonymous_student_id,
        course_id=course_id,
        cache=cache,
        can_execute_unsafe_code=(lambda: can_execute_unsafe_code(course_id)),
        get_python_lib_zip=(lambda: get_python_lib_zip(contentstore, course_id)),
        # TODO: When we merge the descriptor and module systems, we can stop reaching into the mixologist (cpennington)
        mixins=descriptor.runtime.mixologist._mixins,  # pylint: disable=protected-access
        wrappers=block_wrappers,
        get_real_user=user_by_anonymous_id,
        services={
            'fs': FSService(),
            'field-data': field_data,
            'user': DjangoXBlockUserService(user, user_is_staff=user_is_staff),
            'verification': VerificationService(),
            'proctoring': ProctoringService(),
            'milestones': milestones_helpers.get_service(),
            'credit': CreditService(),
            'bookmarks': BookmarksService(user=user),
        },
        get_user_role=lambda: get_user_role(user, course_id),
        descriptor_runtime=descriptor._runtime,  # pylint: disable=protected-access
        rebind_noauth_module_to_user=rebind_noauth_module_to_user,
        user_location=user_location,
        request_token=request_token,
    )

    # pass position specified in URL to module through ModuleSystem
    if position is not None:
        try:
            position = int(position)
        except (ValueError, TypeError):
            log.exception('Non-integer %r passed as position.', position)
            position = None

    system.set('position', position)

    system.set(u'user_is_staff', user_is_staff)
    system.set(u'user_is_admin', bool(has_access(user, u'staff', 'global')))
    system.set(u'user_is_beta_tester', CourseBetaTesterRole(course_id).has_user(user))
    system.set(u'days_early_for_beta', descriptor.days_early_for_beta)

    # make an ErrorDescriptor -- assuming that the descriptor's system is ok
    if has_access(user, u'staff', descriptor.location, course_id):
        system.error_descriptor_class = ErrorDescriptor
    else:
        system.error_descriptor_class = NonStaffErrorDescriptor

    return system, field_data

#.........这里部分代码省略.........
            staff_access = has_access(user, "staff", descriptor, course_id)
            instructor_access = bool(has_access(user, "instructor", descriptor, course_id))
        if staff_access:
            block_wrappers.append(partial(add_staff_markup, user, instructor_access, disable_staff_debug_info))

    # These modules store data using the anonymous_student_id as a key.
    # To prevent loss of data, we will continue to provide old modules with
    # the per-student anonymized id (as we have in the past),
    # while giving selected modules a per-course anonymized id.
    # As we have the time to manually test more modules, we can add to the list
    # of modules that get the per-course anonymized id.
    is_pure_xblock = isinstance(descriptor, XBlock) and not isinstance(descriptor, XModuleDescriptor)
    module_class = getattr(descriptor, "module_class", None)
    is_lti_module = not is_pure_xblock and issubclass(module_class, LTIModule)
    if is_pure_xblock or is_lti_module:
        anonymous_student_id = anonymous_id_for_user(user, course_id)
    else:
        anonymous_student_id = anonymous_id_for_user(user, None)

    field_data = LmsFieldData(descriptor._field_data, student_data)  # pylint: disable=protected-access

    user_is_staff = bool(has_access(user, u"staff", descriptor.location, course_id))

    system = LmsModuleSystem(
        track_function=track_function,
        render_template=render_to_string,
        static_url=settings.STATIC_URL,
        xqueue=xqueue,
        # TODO (cpennington): Figure out how to share info between systems
        filestore=descriptor.runtime.resources_fs,
        get_module=inner_get_module,
        user=user,
        debug=settings.DEBUG,
        hostname=settings.SITE_NAME,
        # TODO (cpennington): This should be removed when all html from
        # a module is coming through get_html and is therefore covered
        # by the replace_static_urls code below
        replace_urls=partial(
            static_replace.replace_static_urls,
            data_directory=getattr(descriptor, "data_dir", None),
            course_id=course_id,
            static_asset_path=static_asset_path or descriptor.static_asset_path,
        ),
        replace_course_urls=partial(static_replace.replace_course_urls, course_key=course_id),
        replace_jump_to_id_urls=partial(
            static_replace.replace_jump_to_id_urls,
            course_id=course_id,
            jump_to_id_base_url=reverse(
                "jump_to_id", kwargs={"course_id": course_id.to_deprecated_string(), "module_id": ""}
            ),
        ),
        node_path=settings.NODE_PATH,
        publish=publish,
        anonymous_student_id=anonymous_student_id,
        course_id=course_id,
        cache=cache,
        can_execute_unsafe_code=(lambda: can_execute_unsafe_code(course_id)),
        get_python_lib_zip=(lambda: get_python_lib_zip(contentstore, course_id)),
        # TODO: When we merge the descriptor and module systems, we can stop reaching into the mixologist (cpennington)
        mixins=descriptor.runtime.mixologist._mixins,  # pylint: disable=protected-access
        wrappers=block_wrappers,
        get_real_user=user_by_anonymous_id,
        services={
            "fs": FSService(),
            "field-data": field_data,
            "user": DjangoXBlockUserService(user, user_is_staff=user_is_staff),
            "reverification": ReverificationService(),
            "proctoring": ProctoringService(),
            "credit": CreditService(),
            "bookmarks": BookmarksService(user=user),
        },
        get_user_role=lambda: get_user_role(user, course_id),
        descriptor_runtime=descriptor._runtime,  # pylint: disable=protected-access
        rebind_noauth_module_to_user=rebind_noauth_module_to_user,
        user_location=user_location,
        request_token=request_token,
    )

    # pass position specified in URL to module through ModuleSystem
    if position is not None:
        try:
            position = int(position)
        except (ValueError, TypeError):
            log.exception("Non-integer %r passed as position.", position)
            position = None

    system.set("position", position)

    system.set(u"user_is_staff", user_is_staff)
    system.set(u"user_is_admin", bool(has_access(user, u"staff", "global")))
    system.set(u"user_is_beta_tester", CourseBetaTesterRole(course_id).has_user(user))
    system.set(u"days_early_for_beta", descriptor.days_early_for_beta)

    # make an ErrorDescriptor -- assuming that the descriptor's system is ok
    if has_access(user, u"staff", descriptor.location, course_id):
        system.error_descriptor_class = ErrorDescriptor
    else:
        system.error_descriptor_class = NonStaffErrorDescriptor

    return system, field_data

def _preview_module_system(request, descriptor, field_data):
    """
    Returns a ModuleSystem for the specified descriptor that is specialized for
    rendering module previews.

    request: The active django request
    descriptor: An XModuleDescriptor
    """

    course_id = descriptor.location.course_key
    display_name_only = (descriptor.category == 'static_tab')

    wrappers = [
        # This wrapper wraps the module in the template specified above
        partial(
            wrap_xblock,
            'PreviewRuntime',
            display_name_only=display_name_only,
            usage_id_serializer=unicode,
            request_token=request_token(request)
        ),

        # This wrapper replaces urls in the output that start with /static
        # with the correct course-specific url for the static content
        partial(replace_static_urls, None, course_id=course_id),
        _studio_wrap_xblock,
    ]

    wrappers_asides = [
        partial(
            wrap_xblock_aside,
            'PreviewRuntime',
            usage_id_serializer=unicode,
            request_token=request_token(request)
        )
    ]

    if settings.FEATURES.get("LICENSING", False):
        # stick the license wrapper in front
        wrappers.insert(0, wrap_with_license)

    services = get_available_xblock_services(request, field_data, course_id)

    return PreviewModuleSystem(
        static_url=settings.STATIC_URL,
        # TODO (cpennington): Do we want to track how instructors are using the preview problems?
        track_function=lambda event_type, event: None,
        filestore=descriptor.runtime.resources_fs,
        get_module=partial(_load_preview_module, request),
        render_template=render_from_lms,
        debug=True,
        replace_urls=partial(static_replace.replace_static_urls, data_directory=None, course_id=course_id),
        user=request.user,
        can_execute_unsafe_code=(lambda: can_execute_unsafe_code(course_id)),
        get_python_lib_zip=(lambda: get_python_lib_zip(contentstore, course_id)),
        mixins=settings.XBLOCK_MIXINS,
        course_id=course_id,
        anonymous_student_id='student',

        # Set up functions to modify the fragment produced by student_view
        wrappers=wrappers,
        wrappers_asides=wrappers_asides,
        error_descriptor_class=ErrorDescriptor,
        get_user_role=lambda: get_user_role(request.user, course_id),
        # Get the raw DescriptorSystem, not the CombinedSystem
        descriptor_runtime=descriptor._runtime,  # pylint: disable=protected-access
        services=services,
    )