Make the validate_formatter use real instances of book metadata. This avoids type errors during validation in, for example, the Kobo driver..

src/calibre/ebooks/metadata/book/base.py

@@ -885,3 +885,39 @@ def field_from_string(field, raw, field_metadata):
     if val is object:
         val = raw
     return val
+
+
+def get_model_metadata_instance():
+    '''
+    Get a metadata instance that contains all the fields in the current database
+    with the fields to a plausible value. This function must only be used in
+    the GUI thread.
+    '''
+    from calibre.gui2 import is_gui_thread
+    if not is_gui_thread():
+        raise ValueError('get_model_metadata_instance() must only be used in the GUI thread')
+
+    mi = Metadata(_('Title'), [_('Author')])
+    mi.author_sort = _('Author Sort')
+    mi.series = ngettext('Series', 'Series', 1)
+    mi.series_index = 3
+    mi.rating = 4.0
+    mi.tags = [_('Tag 1'), _('Tag 2')]
+    mi.languages = ['eng']
+    mi.id = -1
+    from calibre.gui2.ui import get_gui
+    from calibre.utils.date import DEFAULT_DATE
+    fm = get_gui().current_db.new_api.field_metadata
+    mi.set_all_user_metadata(fm.custom_field_metadata())
+    for col in mi.get_all_user_metadata(False):
+        if fm[col]['datatype'] == 'datetime':
+            mi.set(col, DEFAULT_DATE)
+        elif fm[col]['datatype'] in ('int', 'float', 'rating'):
+            mi.set(col, 2)
+        elif fm[col]['datatype'] == 'bool':
+            mi.set(col, False)
+        elif fm[col]['is_multiple']:
+            mi.set(col, [col])
+        else:
+            mi.set(col, col, 1)
+    return mi

src/calibre/gui2/dialogs/template_dialog.py

@@ -44,7 +44,7 @@ from qt.core import (
 
 from calibre import sanitize_file_name
 from calibre.constants import config_dir, iswindows
-from calibre.ebooks.metadata.book.base import Metadata
+from calibre.ebooks.metadata.book.base import get_model_metadata_instance
 from calibre.ebooks.metadata.book.formatter import SafeFormat
 from calibre.gui2 import choose_files, choose_save_file, error_dialog, gprefs, info_dialog, pixmap_to_data, question_dialog, safe_open_url
 from calibre.gui2.dialogs.template_dialog_ui import Ui_TemplateDialog
@@ -52,13 +52,12 @@ from calibre.gui2.dialogs.template_general_info import GeneralInformationDialog
 from calibre.gui2.widgets2 import Dialog, HTMLDisplay
 from calibre.library.coloring import color_row_key, displayable_columns
 from calibre.utils.config_base import tweaks
-from calibre.utils.date import DEFAULT_DATE
 from calibre.utils.ffml_processor import MARKUP_ERROR, FFMLProcessor
 from calibre.utils.formatter import PythonTemplateContext, StopException
 from calibre.utils.formatter_functions import StoredObjectType, formatter_functions
 from calibre.utils.icu import lower as icu_lower
 from calibre.utils.icu import sort_key
-from calibre.utils.localization import localize_user_manual_link, ngettext
+from calibre.utils.localization import localize_user_manual_link
 from calibre.utils.resources import get_path as P
 
 
@@ -718,40 +717,11 @@ class TemplateDialog(QDialog, Ui_TemplateDialog):
         the contents of the field selectors for editing rules.
         '''
         self.fm = fm
-        from calibre.gui2.ui import get_gui
         if mi:
             if not isinstance(mi, (tuple, list)):
                 mi = (mi, )
         else:
-            mi = Metadata(_('Title'), [_('Author')])
+            mi = (get_model_metadata_instance(), )
-            mi.author_sort = _('Author Sort')
-            mi.series = ngettext('Series', 'Series', 1)
-            mi.series_index = 3
-            mi.rating = 4.0
-            mi.tags = [_('Tag 1'), _('Tag 2')]
-            mi.languages = ['eng']
-            mi.id = -1
-            if self.fm is not None:
-                mi.set_all_user_metadata(self.fm.custom_field_metadata())
-            else:
-                # No field metadata. Grab a copy from the current library so
-                # that we can validate any custom column names. The values for
-                # the columns will all be empty, which in some very unusual
-                # cases might cause formatter errors. We can live with that.
-                fm = get_gui().current_db.new_api.field_metadata
-                mi.set_all_user_metadata(fm.custom_field_metadata())
-            for col in mi.get_all_user_metadata(False):
-                if fm[col]['datatype'] == 'datetime':
-                    mi.set(col, DEFAULT_DATE)
-                elif fm[col]['datatype'] in ('int', 'float', 'rating'):
-                    mi.set(col, 2)
-                elif fm[col]['datatype'] == 'bool':
-                    mi.set(col, False)
-                elif fm[col]['is_multiple']:
-                    mi.set(col, [col])
-                else:
-                    mi.set(col, col, 1)
-            mi = (mi, )
         self.mi = mi
         tv = self.template_value
         tv.setColumnCount(3)

src/calibre/utils/formatter.py

@@ -2025,17 +2025,22 @@ class TemplateFormatter(string.Formatter):
             self.restore_state(state)
 
 
-class ValidateFormatter(TemplateFormatter):
+class ValidateFormatter:
-    '''
-    Provides a formatter that substitutes the validation string for every value
     '''
+    Provides a formatter that uses a fake book. This class must be used only
+    in the GUI thread.
 
-    def get_value(self, key, args, kwargs):
+    It is a class instead of a function for compatibility reasons.
-        return self._validation_string
+    '''
 
     def validate(self, template):
-        from calibre.ebooks.metadata.book.base import Metadata
+        from calibre.gui2 import is_gui_thread
-        return self.unsafe_format(template, {}, Metadata(''))
+        if not is_gui_thread():
+            raise ValueError('A ValidateFormatter must only be used in the GUI thread')
+
+        from calibre.ebooks.metadata.book.base import get_model_metadata_instance
+        from calibre.ebooks.metadata.book.formatter import SafeFormat
+        return SafeFormat().unsafe_format(template, {}, get_model_metadata_instance())
 
 
 validation_formatter = ValidateFormatter()