Refactor the author data api for multiple authors

src/calibre/db/cache.py

@@ -161,7 +161,8 @@ class Cache(object):
     def _get_metadata(self, book_id, get_user_categories=True):  # {{{
         mi = Metadata(None, template_cache=self.formatter_template_cache)
         author_ids = self._field_ids_for('authors', book_id)
-        aut_list = [self._author_data(i) for i in author_ids]
+        adata = self._author_data(author_ids)
+        aut_list = [adata[i] for i in author_ids]
         aum = []
         aus = {}
         aul = {}
@@ -388,17 +389,17 @@ class Cache(object):
             raise ValueError('%s is not a many-one or many-many field' % field)
 
     @read_api
-    def author_data(self, author_id):
+    def author_data(self, author_ids):
         '''
         Return author data as a dictionary with keys: name, sort, link
 
-        If no author with the specified id is found an empty dictionary is
-        returned.
+        If no authors with the specified ids are found an empty dictionary is
+        returned. If author_ids is None, data for all authors is returned.
         '''
-        try:
-            return self.fields['authors'].author_data(author_id)
-        except (KeyError, IndexError):
-            return {}
+        af = self.fields['authors']
+        if author_ids is None:
+            author_ids = tuple(af.table.id_map)
+        return {aid:af.author_data(aid) for aid in author_ids if aid in af.table.id_map}
 
     @read_api
     def format_metadata(self, book_id, fmt, allow_cache=True):

src/calibre/db/tests/legacy.py

@@ -243,6 +243,8 @@ class LegacyTest(BaseTest):
             '_set_title', '_set_custom', '_update_author_in_cache',
             # Feeds are now stored in the config folder
             'get_feeds', 'get_feed', 'update_feed', 'remove_feeds', 'add_feed', 'set_feeds',
+            # Obsolete/broken methods
+            'author_id',  # replaced by get_author_id
         }
         SKIP_ARGSPEC = {
             '__init__', 'get_next_series_num_for', 'has_book', 'author_sort_from_authors', 'all_tags',

src/calibre/db/view.py

@@ -189,10 +189,8 @@ class View(object):
         id_ = idx if index_is_id else self.index_to_id(idx)
         with self.cache.read_lock:
             ids = self.cache._field_ids_for('authors', id_)
-            ans = []
-            for id_ in ids:
-                data = self.cache._author_data(id_)
-                ans.append(':::'.join((data['name'], data['sort'], data['link'])))
+            adata = self.cache._author_data(ids)
+            ans = [':::'.join((adata[aid]['name'], adata[aid]['sort'], adata[aid]['link'])) for aid in ids if aid in adata]
         return ':#:'.join(ans) if ans else default_value
 
     def multisort(self, fields=[], subsort=False, only_ids=None):