We're starting to get several functions and operators that directly o…

…perate on fields. I decided to use a naming convention where they begin with "field_". This commit changes the existing function format_date_field() to field_format_date(), adding an alias for the original name for compatibility.

manual/template_lang.rst

@@ -558,10 +558,10 @@ In `GPM` the functions described in `Single Function Mode` all require an additi
 
    format_date(raw_field('pubdate'), 'yyyy')
 
-* ``format_date_field(field_name, format_string)`` -- format the value in the field ``field_name``, which must be the lookup name of date field, either standard or custom. See ``format_date()`` for the formatting codes. This function is much faster than format_date and should be used when you are formatting the value in a field (column). It can't be used for computed dates or dates in string variables. Examples::
+* ``field_format_date(field_name, format_string)`` -- format the value in the field ``field_name``, which must be the lookup name of date field, either standard or custom. See ``format_date()`` for the formatting codes. This function is much faster than format_date and should be used when you are formatting the value in a field (column). It can't be used for computed dates or dates in string variables. Alias: format_date_field. Examples::
 
-   format_date_field('pubdate', 'yyyy.MM.dd')
-   format_date_field('#date_read', 'MMM dd, yyyy')
+   field_format_date('pubdate', 'yyyy.MM.dd')
+   field_format_date('#date_read', 'MMM dd, yyyy')
 
 * ``formats_modtimes(date_format_string)`` -- return a comma-separated list of colon-separated items ``FMT:DATE`` representing modification times for the formats of a book. The ``date_format_string`` parameter specifies how the date is to be formatted. See the ``format_date()`` function for details. You can use the ``select`` function to get the modification time for a specific format. Note that format names are always uppercase, as in EPUB.
 * ``formats_paths()`` -- return a comma-separated list of colon-separated items ``FMT:PATH`` giving the full path to the formats of a book. You can use the select function to get the path for a specific format. Note that format names are always uppercase, as in EPUB.

src/calibre/utils/formatter_functions.py

@@ -1290,21 +1290,23 @@ def evaluate(self, formatter, kwargs, mi, locals, val, format_string):
 
 
 class BuiltinFormatDateField(BuiltinFormatterFunction):
-    name = 'format_date_field'
+    name = 'field_format_date'
     arg_count = 2
     category = 'Formatting values'
-    __doc__ = doc = _("format_date_field(field_name, format_string) -- format "
+    __doc__ = doc = _("field_format_date(field_name, format_string) -- format "
             "the value in the field 'field_name', which must be the lookup name "
             "of date field, either standard or custom. See 'format_date' for "
             "the formatting codes. This function is much faster than format_date "
             "and should be used when you are formatting the value in a field "
             "(column). It can't be used for computed dates or dates in string "
-            "variables. Example: format_date_field('pubdate', 'yyyy.MM.dd')")
+            "variables. Example: format_date_field('pubdate', 'yyyy.MM.dd'). "
+            "Alias: format_date_field")
+    aliases = ['format_date_field']
 
     def evaluate(self, formatter, kwargs, mi, locals, field, format_string):
         try:
             if field not in mi.all_field_keys():
-                return _('Unknown field %s passed to function %s')%(field, 'format_date_field')
+                return _('Unknown field %s passed to function %s')%(field, 'field_format_date')
             val = mi.get(field, None)
             if val is None:
                 s = ''