Most formatting should not allow album-level data to override item-level fields
Recently, we refactored the string-formatting logic for Items so that, consistently, the associated album-level data would override any inconsistent item-level data. Confusing experiences in #853 and #807 have demonstrated that this was probably not a good idea.

We still need this behavior for formatting paths—for directory structure consistency—but we should back off on making it the default. Commands like `list` should show item-level data with no album-level overrides.

diff --git a/beets/dbcore/db.py b/beets/dbcore/db.py
index 5172ad523..756448720 100644
--- a/beets/dbcore/db.py
+++ b/beets/dbcore/db.py
@@ -28,6 +28,50 @@ from .query import MatchQuery, build_sql
 from .types import BASE_TYPE
 
 
+class FormattedMapping(collections.Mapping):
+    """A `dict`-like formatted view of a model.
+
+    The accessor `mapping[key]` returns the formated version of
+    `model[key]` as a unicode string.
+
+    If `for_path` is true, all path separators in the formatted values
+    are replaced.
+    """
+
+    def __init__(self, model, for_path=False):
+        self.for_path = for_path
+        self.model = model
+        self.model_keys = model.keys(True)
+
+    def __getitem__(self, key):
+        if key in self.model_keys:
+            return self._get_formatted(self.model, key)
+        else:
+            raise KeyError(key)
+
+    def __iter__(self):
+        return iter(self.model_keys)
+
+    def __len__(self):
+        return len(self.model_keys)
+
+    def get(self, key, default=u''):
+        return super(FormattedMapping, self).get(key, default)
+
+    def _get_formatted(self, model, key):
+        value = model._type(key).format(model.get(key))
+        if isinstance(value, bytes):
+            value = value.decode('utf8', 'ignore')
+
+        if self.for_path:
+            sep_repl = beets.config['path_sep_replace'].get(unicode)
+            for sep in (os.path.sep, os.path.altsep):
+                if sep:
+                    value = value.replace(sep, sep_repl)
+
+        return value
+
+
 # Abstract base for model classes.
 
 class Model(object):
@@ -380,63 +424,24 @@ class Model(object):
 
     # Formatting and templating.
 
-    @classmethod
-    def _format(cls, key, value, for_path=False):
-        """Format a value as the given field for this model.
-        """
-        # Format the value as a string according to its type.
-        value = cls._type(key).format(value)
-
-        # Formatting must result in a string. To deal with
-        # Python2isms, implicitly convert ASCII strings.
-        assert isinstance(value, basestring), \\
-            u'field formatter must produce strings'
-        if isinstance(value, bytes):
-            value = value.decode('utf8', 'ignore')
-
-        if for_path:
-            sep_repl = beets.config['path_sep_replace'].get(unicode)
-            for sep in (os.path.sep, os.path.altsep):
-                if sep:
-                    value = value.replace(sep, sep_repl)
+    _formatter = FormattedMapping
 
-        return value
-
-    def _get_formatted(self, key, for_path=False):
-        """Get a field value formatted as a string (`unicode` object)
-        for display to the user. If `for_path` is true, then the value
-        will be sanitized for inclusion in a pathname (i.e., path
-        separators will be removed from the value).
-        """
-        return self._format(key, self.get(key), for_path)
-
-    def _formatted_mapping(self, for_path=False):
+    def formatted(self, for_path=False):
         """Get a mapping containing all values on this object formatted
-        as human-readable strings.
-        """
-        return FormattedMapping(self, for_path)
-
-    @property
-    def formatted(self):
-        """A `dict`-like view containing formatted values.
+        as human-readable unicode strings.
         """
-        return self._formatted_mapping(False)
+        return self._formatter(self, for_path)
 
     def evaluate_template(self, template, for_path=False):
         """Evaluate a template (a string or a `Template` object) using
         the object's fields. If `for_path` is true, then no new path
         separators will be added to the template.
         """
-        # Build value mapping.
-        mapping = self._formatted_mapping(for_path)
-
-        # Get template functions.
-        funcs = self._template_funcs()
-
         # Perform substitution.
         if isinstance(template, basestring):
             template = Template(template)
-        return template.substitute(mapping, funcs)
+        return template.substitute(self.formatted(for_path),
+                                   self._template_funcs())
 
     # Parsing.
 
@@ -450,33 +455,6 @@ class Model(object):
         return cls._type(key).parse(string)
 
 
-class FormattedMapping(collections.Mapping):
-    """A `dict`-like formatted view of a model.
-
-    The accessor ``mapping[key]`` returns the formated version of
-    ``model[key]``. The formatting is handled by `model._format()`.
-    """
-    # TODO Move all formatting logic here
-    # TODO Add caching
-
-    def __init__(self, model, for_path=False):
-        self.for_path = for_path
-        self.model = model
-        self.model_keys = model.keys(True)
-
-    def __getitem__(self, key):
-        if key in self.model_keys:
-            return self.model._get_formatted(key, self.for_path)
-        else:
-            raise KeyError(key)
-
-    def __iter__(self):
-        return iter(self.model_keys)
-
-    def __len__(self):
-        return len(self.model_keys)
-
-
 # Database controller and supporting interfaces.
 
 class Results(object):
diff --git a/beets/library.py b/beets/library.py
index 456f51f7b..3119e1bfa 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -216,6 +216,57 @@ class LibModel(dbcore.Model):
         plugins.send('database_change', lib=self._db)
 
 
+class FormattedItemMapping(dbcore.db.FormattedMapping):
+    """Add lookup for album-level fields.
+
+    Album-level fields take precedence if `for_path` is true.
+    """
+
+    def __init__(self, item, for_path=False):
+        super(FormattedItemMapping, self).__init__(item, for_path)
+        self.album = item.get_album()
+        self.album_keys = []
+        if self.album:
+            for key in self.album.keys(True):
+                if key in Album.item_keys or key not in item._fields.keys():
+                    self.album_keys.append(key)
+        self.all_keys = set(self.model_keys).union(self.album_keys)
+
+    def _get(self, key):
+        """Get the value for a key, either from the album or the item.
+        Raise a KeyError for invalid keys.
+        """
+        if self.for_path and key in self.album_keys:
+            return self._get_formatted(self.album, key)
+        elif key in self.model_keys:
+            return self._get_formatted(self.model, key)
+        elif key in self.album_keys:
+            return self._get_formatted(self.album, key)
+        else:
+            raise KeyError(key)
+
+    def __getitem__(self, key):
+        """Get the value for a key. Certain unset values are remapped.
+        """
+        value = self._get(key)
+
+        # `artist` and `albumartist` fields fall back to one another.
+        # This is helpful in path formats when the album artist is unset
+        # on as-is imports.
+        if key == 'artist' and not value:
+            return self._get('albumartist')
+        elif key == 'albumartist' and not value:
+            return self._get('artist')
+        else:
+            return value
+
+    def __iter__(self):
+        return iter(self.all_keys)
+
+    def __len__(self):
+        return len(self.all_keys)
+
+
 class Item(LibModel):
     _table = 'items'
     _flex_table = 'item_attributes'
@@ -296,6 +347,8 @@ class Item(LibModel):
     `write`.
     """
 
+    _formatter = FormattedItemMapping
+
     @classmethod
     def _getters(cls):
         getters = plugins.item_field_getters()
@@ -523,12 +576,6 @@ class Item(LibModel):
 
     # Templating.
 
-    def _formatted_mapping(self, for_path=False):
-        """Get a mapping containing string-formatted values from either
-        this item or the associated album, if any.
-        """
-        return FormattedItemMapping(self, for_path)
-
     def destination(self, fragment=False, basedir=None, platform=None,
                     path_formats=None):
         """Returns the path in the library directory designated for the
@@ -604,56 +651,6 @@ class Item(LibModel):
             return normpath(os.path.join(basedir, subpath))
 
 
-class FormattedItemMapping(dbcore.db.FormattedMapping):
-    """A `dict`-like formatted view of an item that inherits album fields.
-
-    The accessor ``mapping[key]`` returns the formated version of either
-    ``item[key]`` or ``album[key]``. Here `album` is the album
-    associated to `item` if it exists.
-    """
-    def __init__(self, item, for_path=False):
-        super(FormattedItemMapping, self).__init__(item, for_path)
-        self.album = item.get_album()
-        self.album_keys = []
-        if self.album:
-            for key in self.album.keys(True):
-                if key in Album.item_keys or key not in item._fields.keys():
-                    self.album_keys.append(key)
-        self.all_keys = set(self.model_keys).union(self.album_keys)
-
-    def _get(self, key):
-        """Get the value for a key, either from the album or the item.
-        Raise a KeyError for invalid keys.
-        """
-        if key in self.album_keys:
-            return self.album._get_formatted(key, self.for_path)
-        elif key in self.model_keys:
-            return self.model._get_formatted(key, self.for_path)
-        else:
-            raise KeyError(key)
-
-    def __getitem__(self, key):
-        """Get the value for a key. Certain unset values are remapped.
-        """
-        value = self._get(key)
-
-        # `artist` and `albumartist` fields fall back to one another.
-        # This is helpful in path formats when the album artist is unset
-        # on as-is imports.
-        if key == 'artist' and not value:
-            return self._get('albumartist')
-        elif key == 'albumartist' and not value:
-            return self._get('artist')
-        else:
-            return value
-
-    def __iter__(self):
-        return iter(self.all_keys)
-
-    def __len__(self):
-        return len(self.all_keys)
-
-
 class Album(LibModel):
     """Provides access to information about albums stored in a
     library. Reflects the library's "albums" table, including album
@@ -1219,7 +1216,7 @@ class DefaultTemplateFunctions(object):
             return res
 
         # Flatten disambiguation value into a string.
-        disam_value = album._get_formatted(disambiguator, True)
+        disam_value = album.formatted(True).get(disambiguator)
         res = u' [{0}]'.format(disam_value)
         self.lib._memotable[memokey] = res
         return res
diff --git a/beets/ui/__init__.py b/beets/ui/__init__.py
index 1e64cd89c..829089200 100644
--- a/beets/ui/__init__.py
+++ b/beets/ui/__init__.py
@@ -576,8 +576,8 @@ def _field_diff(field, old, new):
         return None
 
     # Get formatted values for output.
-    oldstr = old.formatted.get(field, u'')
-    newstr = new.formatted.get(field, u'')
+    oldstr = old.formatted().get(field, u'')
+    newstr = new.formatted().get(field, u'')
 
     # For strings, highlight changes. For others, colorize the whole
     # thing.
@@ -620,7 +620,7 @@ def show_model_changes(new, old=None, fields=None, always=False):
 
         changes.append(u'  {0}: {1}'.format(
             field,
-            colorize('red', new.formatted[field])
+            colorize('red', new.formatted()[field])
         ))
 
     # Print changes.
diff --git a/test/test_dbcore.py b/test/test_dbcore.py
index e55bd84db..d6e92a1fb 100644
--- a/test/test_dbcore.py
+++ b/test/test_dbcore.py
@@ -255,54 +255,54 @@ class FormatTest(_common.TestCase):
     def test_format_fixed_field(self):
         model = TestModel1()
         model.field_one = u'caf\\xe9'
-        value = model._get_formatted('field_one')
+        value = model.formatted().get('field_one')
         self.assertEqual(value, u'caf\\xe9')
 
     def test_format_flex_field(self):
         model = TestModel1()
         model.other_field = u'caf\\xe9'
-        value = model._get_formatted('other_field')
+        value = model.formatted().get('other_field')
         self.assertEqual(value, u'caf\\xe9')
 
     def test_format_flex_field_bytes(self):
         model = TestModel1()
         model.other_field = u'caf\\xe9'.encode('utf8')
-        value = model._get_formatted('other_field')
+        value = model.formatted().get('other_field')
         self.assertTrue(isinstance(value, unicode))
         self.assertEqual(value, u'caf\\xe9')
 
     def test_format_unset_field(self):
         model = TestModel1()
-        value = model._get_formatted('other_field')
+        value = model.formatted().get('other_field')
         self.assertEqual(value, u'')
 
     def test_format_typed_flex_field(self):
         model = TestModel1()
         model.some_float_field = 3.14159265358979
-        value = model._get_formatted('some_float_field')
+        value = model.formatted().get('some_float_field')
         self.assertEqual(value, u'3.1')
 
 
 class FormattedMappingTest(_common.TestCase):
     def test_keys_equal_model_keys(self):
         model = TestModel1()
-        formatted = model._formatted_mapping()
+        formatted = model.formatted()
         self.assertEqual(set(model.keys(True)), set(formatted.keys()))
 
     def test_get_unset_field(self):
         model = TestModel1()
-        formatted = model._formatted_mapping()
+        formatted = model.formatted()
         with self.assertRaises(KeyError):
             formatted['other_field']
 
-    def test_get_method_with_none_default(self):
+    def test_get_method_with_default(self):
         model = TestModel1()
-        formatted = model._formatted_mapping()
-        self.assertIsNone(formatted.get('other_field'))
+        formatted = model.formatted()
+        self.assertEqual(formatted.get('other_field'), u'')
 
     def test_get_method_with_specified_default(self):
         model = TestModel1()
-        formatted = model._formatted_mapping()
+        formatted = model.formatted()
         self.assertEqual(formatted.get('other_field', 'default'), 'default')
 
 
diff --git a/test/test_library.py b/test/test_library.py
index aac58b9e9..458863190 100644
--- a/test/test_library.py
+++ b/test/test_library.py
@@ -340,37 +340,37 @@ class DestinationTest(_common.TestCase):
         with _common.platform_posix():
             name = os.path.join('a', 'b')
             self.i.title = name
-            newname = self.i._get_formatted('title')
+            newname = self.i.formatted().get('title')
         self.assertEqual(name, newname)
 
     def test_get_formatted_pads_with_zero(self):
         with _common.platform_posix():
             self.i.track = 1
-            name = self.i._get_formatted('track')
+            name = self.i.formatted().get('track')
         self.assertTrue(name.startswith('0'))
 
     def test_get_formatted_uses_kbps_bitrate(self):
         with _common.platform_posix():
             self.i.bitrate = 12345
-            val = self.i._get_formatted('bitrate')
+            val = self.i.formatted().get('bitrate')
         self.assertEqual(val, u'12kbps')
 
     def test_get_formatted_uses_khz_samplerate(self):
         with _common.platform_posix():
             self.i.samplerate = 12345
-            val = self.i._get_formatted('samplerate')
+            val = self.i.formatted().get('samplerate')
         self.assertEqual(val, u'12kHz')
 
     def test_get_formatted_datetime(self):
         with _common.platform_posix():
             self.i.added = 1368302461.210265
-            val = self.i._get_formatted('added')
+            val = self.i.formatted().get('added')
         self.assertTrue(val.startswith('2013'))
 
     def test_get_formatted_none(self):
         with _common.platform_posix():
             self.i.some_other_field = None
-            val = self.i._get_formatted('some_other_field')
+            val = self.i.formatted().get('some_other_field')
         self.assertEqual(val, u'')
 
     def test_artist_falls_back_to_albumartist(self):
@@ -462,23 +462,35 @@ class DestinationTest(_common.TestCase):
 
 class ItemFormattedMappingTest(_common.LibTestCase):
     def test_formatted_item_value(self):
-        formatted = self.i._formatted_mapping()
+        formatted = self.i.formatted()
         self.assertEqual(formatted['artist'], 'the artist')
 
     def test_get_unset_field(self):
-        formatted = self.i._formatted_mapping()
+        formatted = self.i.formatted()
         with self.assertRaises(KeyError):
             formatted['other_field']
 
-    def test_get_method_with_none_default(self):
-        formatted = self.i._formatted_mapping()
-        self.assertIsNone(formatted.get('other_field'))
+    def test_get_method_with_default(self):
+        formatted = self.i.formatted()
+        self.assertEqual(formatted.get('other_field'), u'')
 
     def test_get_method_with_specified_default(self):
-        formatted = self.i._formatted_mapping()
+        formatted = self.i.formatted()
         self.assertEqual(formatted.get('other_field', 'default'), 'default')
 
-    def test_album_field_overrides_item_field(self):
+    def test_item_precedence(self):
+        album = self.lib.add_album([self.i])
+        album['artist'] = 'foo'
+        album.store()
+        self.assertNotEqual('foo', self.i.formatted().get('artist'))
+
+    def test_album_flex_field(self):
+        album = self.lib.add_album([self.i])
+        album['flex'] = 'foo'
+        album.store()
+        self.assertEqual('foo', self.i.formatted().get('flex'))
+
+    def test_album_field_overrides_item_field_for_path(self):
         # Make the album inconsistent with the item.
         album = self.lib.add_album([self.i])
         album.album = 'foo'
@@ -487,23 +499,23 @@ class ItemFormattedMappingTest(_common.LibTestCase):
         self.i.store()
 
         # Ensure the album takes precedence.
-        formatted = self.i._formatted_mapping()
+        formatted = self.i.formatted(for_path=True)
         self.assertEqual(formatted['album'], 'foo')
 
     def test_artist_falls_back_to_albumartist(self):
         self.i.artist = ''
-        formatted = self.i._formatted_mapping()
+        formatted = self.i.formatted()
         self.assertEqual(formatted['artist'], 'the album artist')
 
     def test_albumartist_falls_back_to_artist(self):
         self.i.albumartist = ''
-        formatted = self.i._formatted_mapping()
+        formatted = self.i.formatted()
         self.assertEqual(formatted['albumartist'], 'the artist')
 
     def test_both_artist_and_albumartist_empty(self):
         self.i.artist = ''
         self.i.albumartist = ''
-        formatted = self.i._formatted_mapping()
+        formatted = self.i.formatted()
         self.assertEqual(formatted['albumartist'], '')
 
 
['test/test_library.py', 'beets/ui/__init__.py', 'beets/dbcore/db.py', 'beets/library.py', 'test/test_dbcore.py']