From 0ada2ad42bf3f05fd780d989ed640bc76163e99f Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 9 Mar 2020 09:36:48 +0530
Subject: [PATCH] DB: Ensure that set_metadata() sets author_sort to a correct
 value if the Metadata object has authors but no author_sort. Fixes #1116
 (Generate an author_sort in fetch-ebook-metadata output)

---
 src/calibre/db/cache.py         | 12 ++++++++++--
 src/calibre/db/tests/writing.py |  7 +++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index 11e02d083b..f2b01b68b5 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -26,7 +26,7 @@ from calibre.db.tables import VirtualTable
 from calibre.db.write import get_series_values, uniq
 from calibre.db.lazy import FormatMetadata, FormatsList, ProxyMetadata
 from calibre.ebooks import check_ebook_format
-from calibre.ebooks.metadata import string_to_authors, author_to_author_sort
+from calibre.ebooks.metadata import string_to_authors, author_to_author_sort, authors_to_sort_string
 from calibre.ebooks.metadata.book.base import Metadata
 from calibre.ebooks.metadata.opf2 import metadata_to_opf
 from calibre.ptempfile import (base_dir, PersistentTemporaryFile,
@@ -1297,6 +1297,7 @@ class Cache(object):
         if set_title and mi.title:
             path_changed = True
             set_field('title', mi.title)
+        authors_changed = False
         if set_authors:
             path_changed = True
             if not mi.authors:
@@ -1305,6 +1306,7 @@ class Cache(object):
             for a in mi.authors:
                 authors += string_to_authors(a)
             set_field('authors', authors)
+            authors_changed = True
 
         if path_changed:
             self._update_path({book_id})
@@ -1339,7 +1341,13 @@ class Cache(object):
                     if val is not None:
                         protected_set_field(field, val)
 
-                for field in ('author_sort', 'publisher', 'series', 'tags', 'comments',
+                val = mi.get('author_sort', None)
+                if authors_changed and (not val or mi.is_null('author_sort')):
+                    val = authors_to_sort_string(mi.authors)
+                if authors_changed or (force_changes and val is not None) or not mi.is_null('author_sort'):
+                    protected_set_field('author_sort', val)
+
+                for field in ('publisher', 'series', 'tags', 'comments',
                     'languages', 'pubdate'):
                     val = mi.get(field, None)
                     if (force_changes and val is not None) or not mi.is_null(field):
diff --git a/src/calibre/db/tests/writing.py b/src/calibre/db/tests/writing.py
index 74c43aee4c..8d858c12d9 100644
--- a/src/calibre/db/tests/writing.py
+++ b/src/calibre/db/tests/writing.py
@@ -11,6 +11,7 @@ from functools import partial
 from io import BytesIO
 
 from calibre.ebooks.metadata import author_to_author_sort, title_sort
+from calibre.ebooks.metadata.book.base import Metadata
 from calibre.utils.date import UNDEFINED_DATE
 from calibre.db.tests.base import BaseTest, IMG
 from polyglot.builtins import iteritems, itervalues, unicode_type
@@ -436,6 +437,12 @@ class WritingTest(BaseTest):
         cache.set_metadata(3, mi)
         self.assertEqual(set(otags), set(cache.field_for('tags', 3)), 'case changes should not be allowed in set_metadata')
 
+        # test that setting authors without author sort results in an
+        # auto-generated authors sort
+        mi = Metadata('empty', ['a1', 'a2'])
+        cache.set_metadata(1, mi)
+        self.assertEqual('a1 & a2', cache.field_for('author_sort', 1))
+
     # }}}
 
     def test_conversion_options(self):  # {{{