Merge pull request #9 from slogsdon7/master

Read_only field style and tests

Author: sampsyo

mediafile.py

@@ -450,7 +450,7 @@ class StorageStyle(object):
     """
 
     def __init__(self, key, as_type=six.text_type, suffix=None,
-                 float_places=2):
+                 float_places=2, read_only=False):
         """Create a basic storage strategy. Parameters:
 
         - `key`: The key on the Mutagen file object used to access the
@@ -462,11 +462,16 @@ def __init__(self, key, as_type=six.text_type, suffix=None,
         - `float_places`: When the value is a floating-point number and
           encoded as a string, the number of digits to store after the
           decimal point.
+        - `read_only`: When true, writing to this field is disabled.
+           Primary use case is so wrongly named fields can be addressed
+           in a graceful manner. This does not block the delete method.
+
         """
         self.key = key
         self.as_type = as_type
         self.suffix = suffix
         self.float_places = float_places
+        self.read_only = read_only
 
         # Convert suffix to correct string type.
         if self.suffix and self.as_type is six.text_type \
@@ -1198,7 +1203,8 @@ def __set__(self, mediafile, value):
         if value is None:
             value = self._none_value()
         for style in self.styles(mediafile.mgfile):
-            style.set(mediafile.mgfile, value)
+            if not style.read_only:
+                style.set(mediafile.mgfile, value)
 
     def __delete__(self, mediafile):
         for style in self.styles(mediafile.mgfile):
@@ -1233,7 +1239,8 @@ def __get__(self, mediafile, _):
 
     def __set__(self, mediafile, values):
         for style in self.styles(mediafile.mgfile):
-            style.set_list(mediafile.mgfile, values)
+            if not style.read_only:
+                style.set_list(mediafile.mgfile, values)
 
     def single_field(self):
         """Returns a ``MediaField`` descriptor that gets and sets the

test/rsrc/read_only_tag.m4a

@@ -403,6 +403,41 @@ def test_image_encoding(self):
                 self._delete_test()
 
 
+class ReadOnlyTagTest(unittest.TestCase, _common.TempDirMixin):
+    def setUp(self):
+        self.create_temp_dir()
+        self.key = "READ_ONLY_TEST"
+        self.field = mediafile.MediaField(
+            mediafile.MP3StorageStyle(self.key, read_only=True),
+            mediafile.MP4StorageStyle(
+                "----:com.apple.iTunes:" + self.key, read_only=True),
+            mediafile.StorageStyle(self.key, read_only=True),
+            mediafile.ASFStorageStyle(self.key, read_only=True),
+        )
+
+        if "read_only_test" not in mediafile.MediaFile.fields():
+            mediafile.MediaFile.add_field("read_only_test", self.field)
+
+    def test_read(self):
+        path = os.path.join(_common.RSRC, b'empty.flac')
+        mf = mediafile.MediaFile(path)
+        mf.mgfile.tags[self.key] = "don't"
+        self.assertEqual("don't", mf.read_only_test)
+
+    def test_write(self):
+        src = os.path.join(_common.RSRC, b'empty.flac')
+        path = os.path.join(self.temp_dir, b'test.flac')
+        shutil.copy(src, path)
+        mf = mediafile.MediaFile(path)
+        mf.read_only_field = "something terrible"
+        mf.path = os.path.join(self.temp_dir, b'test.flac')
+        mf.save()
+        self.assertNotIn(self.key, mf.mgfile.tags)
+
+    def tearDown(self):
+        self.remove_temp_dir()
+
+
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)