...

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

@@ -514,8 +514,9 @@ class Metadata(object):
             fmt('Rights', unicode(self.rights))
         for key in self.user_metadata_keys():
             val = self.get(key, None)
-            (name, val) = self.format_field(key)
+            if val:
-            fmt(name, unicode(val))
+                (name, val) = self.format_field(key)
+                fmt(name, unicode(val))
         return u'\n'.join(ans)
 
     def to_html(self):
@@ -538,7 +539,7 @@ class Metadata(object):
             ans += [(_('Rights'), unicode(self.rights))]
         for key in self.user_metadata_keys():
             val = self.get(key, None)
-            if val is not None:
+            if val:
                 (name, val) = self.format_field(key)
                 ans += [(name, val)]
         for i, x in enumerate(ans):

src/calibre/gui2/ui.py

@@ -533,6 +533,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, # {{{
             # Save the current field_metadata for applications like calibre2opds
             # Goes here, because if cf is valid, db is valid.
             db.prefs['field_metadata'] = db.field_metadata.all_metadata()
+            db.commit_dirty_cache()
             if DEBUG and db.gm_count > 0:
                 print 'get_metadata cache: {0:d} calls, {1:4.2f}% misses'.format(
                         db.gm_count, (db.gm_missed*100.0)/db.gm_count)

src/calibre/library/database2.py

@@ -340,6 +340,7 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         setattr(self, 'title_sort', functools.partial(self.get_property,
                 loc=self.FIELD_MAP['sort']))
 
+        self.dirtied_cache = set()
         d = self.conn.get('SELECT book FROM metadata_dirtied', all=True)
         for x in d:
             self.dirtied_queue.put(x[0])
@@ -585,12 +586,19 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
             if remove_from_dirtied:
                 self.conn.execute('DELETE FROM metadata_dirtied WHERE book=?',
                         (book_id,))
+                # if a later exception prevents the commit, then the dirtied
+                # table will still have the book. No big deal, because the OPF
+                # is there and correct. We will simply do it again on next
+                # start
+                self.dirtied_cache.discard(book_id)
         if commit:
             self.conn.commit()
         return True
 
     def dirtied(self, book_ids, commit=True):
         for book in book_ids:
+            if book in self.dirtied_cache:
+                continue
             try:
                 self.conn.execute(
                     'INSERT INTO metadata_dirtied (book) VALUES (?)',
@@ -598,10 +606,28 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
                 self.dirtied_queue.put(book)
             except IntegrityError:
                 # Already in table
-                continue
+                pass
+            # If the commit doesn't happen, then our cache will be wrong. This
+            # could lead to a problem because we won't put the book back into
+            # the dirtied table. We deal with this by writing the dirty cache
+            # back to the table on GUI exit. Not perfect, but probably OK
+            self.dirtied_cache.add(book)
         if commit:
             self.conn.commit()
 
+    def commit_dirty_cache(self):
+        '''
+        Set the dirty indication for every book in the cache. The vast majority
+        of the time, the indication will already be set. However, sometimes
+        exceptions may have prevented a commit, which may remove some dirty
+        indications from the DB. This call will put them back. Note that there
+        is no problem with setting a dirty indication for a book that isn't in
+        fact dirty. Just wastes a few cycles.
+        '''
+        book_ids = list(self.dirtied_cache)
+        self.dirtied_cache = set()
+        self.dirtied(book_ids)
+
     def get_metadata(self, idx, index_is_id=False, get_cover=False):
         '''
         Convenience method to return metadata as a :class:`Metadata` object.

src/calibre/manual/template_lang.rst

@@ -17,14 +17,14 @@ For the book "The Foundation" by "Isaac Asimov" it will become::
 
     Asimov, Isaac/The Foundation/The Foundation - Isaac Asimov
 
-You can use all the various metadata fields available in calibre in a template, including any custom columns you have created yourself. To find out the template name for a column simply hover your mouse over the column header. Names for custom fields (columns you have created yourself) always have a # as the first character. For series type custom fields, there is always an additional field named ``#seriesname_index`` that becomes the series index for that series. So if you have a custom series field named #myseries, there will also be a field named #myseries_index.
+You can use all the various metadata fields available in calibre in a template, including any custom columns you have created yourself. To find out the template name for a column simply hover your mouse over the column header. Names for custom fields (columns you have created yourself) always have a # as the first character. For series type custom fields, there is always an additional field named ``#seriesname_index`` that becomes the series index for that series. So if you have a custom series field named ``#myseries``, there will also be a field named ``#myseries_index``.
 
 In addition to the column based fields, you also can use::
 
     {formats} - A list of formats available in the calibre library for a book
     {isbn}    - The ISBN number of the book
 
-If a particular book does not have a particular piece of metadata, the field in the template is automatically removed for that book. So for example::
+If a particular book does not have a particular piece of metadata, the field in the template is automatically removed for that book. Consider, for example::
 
     {author_sort}/{series}/{title} {series_index}
 
@@ -44,19 +44,19 @@ Advanced formatting
 
 You can do more than just simple substitution with the templates. You can also conditionally include text and control how the substituted data is formatted.
 
-First, conditionally including text. There are cases where you might want to have text appear in the output only if a field is not empty. A common case is series and series_index, where you want either nothing or the two values with a hyphen between them. Calibre handles this case using a special field syntax.
+First, conditionally including text. There are cases where you might want to have text appear in the output only if a field is not empty. A common case is ``series`` and ``series_index``, where you want either nothing or the two values with a hyphen between them. Calibre handles this case using a special field syntax.
 
 For example, assume you want to use the template::
 
         {series} - {series_index} - {title}
 
-If the book has no series, the answer will be '- - title'. Many people would rather the result be simply 'title', without the hyphens. To do this, use the extended syntax ``{field:|prefix_text|suffix_text}``. When you use this syntax, if field has the value SERIES then the result will be prefix_textSERIESsuffix_text. If field has no value, then the result will be the empty string (nothing). The prefix and suffix can contain blanks.
+If the book has no series, the answer will be ``- - title``. Many people would rather the result be simply ``title``, without the hyphens. To do this, use the extended syntax ``{field:|prefix_text|suffix_text}``. When you use this syntax, if field has the value SERIES then the result will be ``prefix_textSERIESsuffix_text``. If field has no value, then the result will be the empty string (nothing); the prefix and suffix are ignored. The prefix and suffix can contain blanks.
 
 Using this syntax, we can solve the above series problem with the template::
 
         {series}{series_index:| - | - }{title}
 
-The hyphens will be included only if the book has a series index.
+The hyphens will be included only if the book has a series index, which it will have only if it has a series.
 
 Notes: you must include the : character if you want to use a prefix or a suffix. You must either use no \| characters or both of them; using one, as in ``{field:| - }``, is not allowed. It is OK not to provide any text for one side or the other, such as in ``{series:|| - }``. Using ``{title:||}`` is the same as using ``{title}``.
 
@@ -85,7 +85,7 @@ Advanced features
 Using templates in custom columns
 ----------------------------------
 
-There are sometimes cases where you want to display metadata that |app| does not normally display, or to display data in a way different from how |app| normally does. For example, you might want to display the ISBN, a field that |app| does not display. You can use custom columns for this. To do so, you create a column with the type 'column built from other columns' (hereafter called composite columns), enter a template, and |app| will display in the column the result of evaluating that template. To display the isbn, create the column and enter ``{isbn}`` into the template box. To display a column containing the values of two series custom columns separated by a comma, use ``{#series1:||,}{#series2}``.
+There are sometimes cases where you want to display metadata that |app| does not normally display, or to display data in a way different from how |app| normally does. For example, you might want to display the ISBN, a field that |app| does not display. You can use custom columns for this by creating a column with the type 'column built from other columns' (hereafter called composite columns), and entering a template. Result: |app| will display a column showing the result of evaluating that template. To display the ISBN, create the column and enter ``{isbn}`` into the template box. To display a column containing the values of two series custom columns separated by a comma, use ``{#series1:||,}{#series2}``.
 
 Composite columns can use any template option, including formatting.
 
@@ -98,7 +98,7 @@ Suppose you want to display the value of a field in upper case, when that field
 
 Function references replace the formatting specification, going after the : and before the first ``|`` or the closing ``}``. Functions must always end with ``()``. Some functions take extra values (arguments), and these go inside the ``()``.
 
-The syntax for using functions is ``{field:function(arguments)}``, or ``{field:function(arguments)|prefix|suffix}``. Argument values cannot contain a comma, because it is used to separate arguments. Functions return the value of the field used in the template, suitably modified.
+The syntax for using functions is ``{field:function(arguments)}``, or ``{field:function(arguments)|prefix|suffix}``. Argument values cannot contain a comma, because it is used to separate arguments. The last (or only) argument cannot contain a closing parenthesis ( ')' ). Functions return the value of the field used in the template, suitably modified.
 
 The functions available are: