Tests for the new formatter db functions, and fixes for the errors that the tests found.

I left in the code I used to select specific tests. Yank it out if you don't want it.

src/calibre/db/tests/reading.py

@@ -745,3 +745,97 @@ class ReadingTest(BaseTest):
                 val = val.encode('utf-8')
             self.assertEqual(got, val)
     # }}}
+
+    def test_template_db_functions(self):  # {{{
+        from calibre.ebooks.metadata.book.base import Metadata
+        from calibre.ebooks.metadata.book.formatter import SafeFormat
+        formatter = SafeFormat()
+
+        db = self.init_cache(self.library_path)
+        db.create_custom_column('mult', 'CC1', 'composite', True, display={'composite_template': 'b,a,c'})
+
+        db = self.init_legacy(self.library_path)
+        class GetGuiAns():
+            current_db = None
+        get_gui_ans = GetGuiAns()
+        get_gui_ans.current_db = db
+        from calibre.gui2.ui import get_gui
+        get_gui.ans = get_gui_ans
+
+        try:
+            # need an empty metadata object to pass to the formatter
+            mi = Metadata('A', 'B')
+
+            # test counting books matching the search
+            v = formatter.safe_format('program: book_count("series:true", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(v, '2')
+
+            # test counting books when none match the search
+            v = formatter.safe_format('program: book_count("series:afafaf", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(v, '0')
+
+            # test is_multiple values
+            v = formatter.safe_format('program: book_values("tags", "tags:true", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(set(v.split(',')), {'Tag One', 'News', 'Tag Two'})
+
+            # test not is_multiple values
+            v = formatter.safe_format('program: book_values("series", "series:true", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(v, 'A Series One')
+
+            # test returning values for a column not searched for
+            v = formatter.safe_format('program: book_values("tags", "series:\\"A Series One\\"", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(set(v.split(',')), {'Tag One', 'News', 'Tag Two'})
+
+            # test getting a singleton value from books where the column is empty
+            v = formatter.safe_format('program: book_values("series", "series:false", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(v, '')
+
+            # test getting a multiple value from books where the column is empty
+            v = formatter.safe_format('program: book_values("tags", "tags:false", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(v, '')
+
+            # test fetching an unknown column
+            v = formatter.safe_format('program: book_values("taaags", "tags:false", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(v, "TEMPLATE ERROR The column taaags doesn't exist")
+
+            # test finding all books
+            v = formatter.safe_format('program: book_values("id", "title:true", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(set(v.split(',')), {'1', '2', '3'})
+
+            # test getting value of a composite
+            v = formatter.safe_format('program: book_values("#mult", "id:1", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(set(v.split(',')), {'b', 'c', 'a'})
+
+            # test getting value of a custom float
+            v = formatter.safe_format('program: book_values("#float", "title:true", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(set(v.split(',')), {'20.02', '10.01'})
+
+            # test getting value of an int (rating)
+            v = formatter.safe_format('program: book_values("rating", "title:true", ",", 0)', {}, 'TEMPLATE ERROR', mi)
+            self.assertEqual(set(v.split(',')), {'4', '6'})
+        finally:
+            get_gui.ans = None
+    # }}}
+
+
+import unittest, importlib, sys
+from calibre.utils.run_tests import run_tests, filter_tests_by_name
+
+
+if __name__ == '__main__':
+    try:
+        import init_calibre  # noqa
+    except ImportError:
+        pass
+    tests = sys.argv[1:]
+    sys.argv = sys.argv[0:1]
+
+    def find_tests():
+        m = importlib.import_module('calibre.db.tests.reading')
+        suite = unittest.TestSuite([unittest.defaultTestLoader.loadTestsFromModule(m)])
+        if tests:
+            return filter_tests_by_name(suite, *tests)
+        else:
+            return suite
+
+    run_tests(find_tests)

src/calibre/utils/formatter_functions.py

@@ -2265,14 +2265,25 @@ class BuiltinBookValues(BuiltinFormatterFunction):
         if (not tweaks.get('allow_template_database_functions_in_composites', False) and
                 formatter.global_vars.get(rendering_composite_name, None)):
             raise ValueError(_('The book_values() function cannot be used in a composite column'))
-        with suppress(Exception):
+        try:
             from calibre.gui2.ui import get_gui
             db = get_gui().current_db
+        except:
+            return _('This function can be used only in the GUI')
+        if column not in db.field_metadata:
+            raise ValueError(_("The column {} doesn't exist").format(column))
+        try:
             ids = db.search_getting_ids(query, None, use_virtual_library=use_vl != '0')
-            ff = db.new_api.field_for
-            s = {ff(column, id_) for id_ in ids if ff(column, id_)}
+            s = set()
+            for id_ in ids:
+                f = db.new_api.get_proxy_metadata(id_).get(column, None)
+                if isinstance(f, (tuple, list)):
+                    s.update(f)
+                elif f:
+                    s.add(str(f))
             return sep.join(s)
-        return _('This function can be used only in the GUI')
+        except Exception as e:
+            raise ValueError(e)
 
 
 _formatter_builtins = [