Add new formatter function "current_virtual_library_name().

manual/template_lang.rst

@@ -389,6 +389,7 @@ In `GPM` the functions described in `Single Function Mode` all require an additi
 * ``connected_device_uuid(storage_location_key)`` -- if a device is connected then return the device uuid (unique id), otherwise return the empty string. Each storage location on a device has a different uuid. The ``storage_location_key`` location names are ``'main'``, ``'carda'`` and ``'cardb'``. This function works only in the GUI.
 * ``current_library_name()`` -- return the last name on the path to the current calibre library.
 * ``current_library_path()`` -- return the full path to the current calibre library.
+* ``current_virtual_library_name()`` -- return the name of the current virtual library if there is one, otherwise the empty string. Library name case is preserved. Example: ``program: current_virtual_library_name()``. This function works only in the GUI.
 * ``date_arithmetic(date, calc_spec, fmt)`` -- Calculate a new date from ``date`` using ``calc_spec``. Return the new date formatted according to optional ``fmt``: if not supplied then the result will be in ISO format. The calc_spec is a string formed by concatenating pairs of ``vW`` (``valueWhat``) where ``v`` is a possibly-negative number and W is one of the following letters:
 
     * ``s``: add ``v`` seconds to ``date``

src/calibre/utils/formatter_functions.py

@@ -1762,6 +1762,22 @@ class BuiltinVirtualLibraries(BuiltinFormatterFunction):
         return _('This function can be used only in the GUI')
 
 
+class BuiltinCurrentVirtualLibraryName(BuiltinFormatterFunction):
+    name = 'current_virtual_library_name'
+    arg_count = 0
+    category = 'Get values from metadata'
+    __doc__ = doc = _('current_virtual_library_name() -- '
+            'return the name of the current virtual library if there is one, '
+            'otherwise the empty string. Library name case is preserved. '
+            'Example: "program: current_virtual_library_name()".')
+
+    def evaluate(self, formatter, kwargs, mi, locals):
+        with suppress(Exception):
+            from calibre.gui2.ui import get_gui
+            return get_gui().current_db.data.get_base_restriction_name()
+        return _('This function can be used only in the GUI')
+
+
 class BuiltinUserCategories(BuiltinFormatterFunction):
     name = 'user_categories'
     arg_count = 0
@@ -2086,7 +2102,7 @@ _formatter_builtins = [
     BuiltinCapitalize(), BuiltinCharacter(), BuiltinCheckYesNo(), BuiltinCeiling(),
     BuiltinCmp(), BuiltinConnectedDeviceName(), BuiltinConnectedDeviceUUID(), BuiltinContains(),
     BuiltinCount(), BuiltinCurrentLibraryName(), BuiltinCurrentLibraryPath(),
-    BuiltinDateArithmetic(),
+    BuiltinCurrentVirtualLibraryName(), BuiltinDateArithmetic(),
     BuiltinDaysBetween(), BuiltinDivide(), BuiltinEval(), BuiltinFirstNonEmpty(),
     BuiltinField(), BuiltinFieldExists(),
     BuiltinFinishFormatting(), BuiltinFirstMatchingCmp(), BuiltinFloor(),