gh-75223: Deprecate undotted extensions in `mimetypes.MimeTypes.add_type` (#128638)

Co-authored-by: Petr Viktorin <encukou@gmail.com>
Co-authored-by: Daniel Watkins <daniel@daniel-watkins.co.uk>
Co-authored-by: Oleg Iarygin <oleg@arhadthedev.net>

diff --git a/Doc/deprecations/pending-removal-in-3.16.rst b/Doc/deprecations/pending-removal-in-3.16.rst
index acb53198bdc07e464f63a94d5d36b578bc38f094..90183f1ff233c13f9bb1f0eb97b1f862155df737 100644 (file)
--- a/Doc/deprecations/pending-removal-in-3.16.rst
+++ b/Doc/deprecations/pending-removal-in-3.16.rst
@@ -61,6 +61,14 @@ Pending removal in Python 3.16
   * Calling the Python implementation of :func:`functools.reduce` with *function*
     or *sequence* as keyword arguments has been deprecated since Python 3.14.
 
+* :mod:`mimetypes`:
+
+  * Valid extensions start with a '.' or are empty for
+    :meth:`mimetypes.MimeTypes.add_type`.
+    Undotted extensions are deprecated and will
+    raise a :exc:`ValueError` in Python 3.16.
+    (Contributed by Hugo van Kemenade in :gh:`75223`.)
+
 * :mod:`shutil`:
 
   * The :class:`!ExecError` exception

diff --git a/Doc/library/mimetypes.rst b/Doc/library/mimetypes.rst
index 5af69455032d71a2edb8394a7cb03e701195bb4f..13511b16a0ed8ce7e33f854e34608943e820f330 100644 (file)
--- a/Doc/library/mimetypes.rst
+++ b/Doc/library/mimetypes.rst
@@ -301,13 +301,18 @@ than one MIME-type database; it provides an interface similar to the one of the
 
    .. method:: MimeTypes.add_type(type, ext, strict=True)
 
-      Add a mapping from the MIME type *type* to the extension *ext*. When the
+      Add a mapping from the MIME type *type* to the extension *ext*.
+      Valid extensions start with a '.' or are empty. When the
       extension is already known, the new type will replace the old one. When the type
       is already known the extension will be added to the list of known extensions.
 
       When *strict* is ``True`` (the default), the mapping will be added to the
       official MIME types, otherwise to the non-standard ones.
 
+      .. deprecated-removed:: 3.14 3.16
+         Invalid, undotted extensions will raise a
+         :exc:`ValueError` in Python 3.16.
+
 
 .. _mimetypes-cli:
 

diff --git a/Doc/whatsnew/3.14.rst b/Doc/whatsnew/3.14.rst
index 95a4d0d5822362f531971b29bae821a68f0742c7..82ef636778183b4826d46072c360b35de2f0dde4 100644 (file)
--- a/Doc/whatsnew/3.14.rst
+++ b/Doc/whatsnew/3.14.rst
@@ -1589,6 +1589,13 @@ Deprecated
   and scheduled for removal in Python 3.16. Define handlers with the *stream*
   argument instead. (Contributed by Mariusz Felisiak in :gh:`115032`.)
 
+* :mod:`mimetypes`:
+  Valid extensions start with a '.' or are empty for
+  :meth:`mimetypes.MimeTypes.add_type`.
+  Undotted extensions are deprecated and will
+  raise a :exc:`ValueError` in Python 3.16.
+  (Contributed by Hugo van Kemenade in :gh:`75223`.)
+
 * :mod:`!nturl2path`: This module is now deprecated. Call
   :func:`urllib.request.url2pathname` and :func:`~urllib.request.pathname2url`
   instead.

diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index de842eabea80932c3f9608b0ac435d877d5fb5f6..e93e1d5a03a45491ba02531a2254cfd94803039d 100644 (file)
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -89,7 +89,19 @@ class MimeTypes:
         If strict is true, information will be added to
         list of standard types, else to the list of non-standard
         types.
+
+        Valid extensions are empty or start with a '.'.
         """
+        if ext and not ext.startswith('.'):
+            from warnings import _deprecated
+
+            _deprecated(
+                "Undotted extensions",
+                "Using undotted extensions is deprecated and "
+                "will raise a ValueError in Python {remove}",
+                remove=(3, 16),
+            )
+
         if not type:
             return
         self.types_map[strict][ext] = type

diff --git a/Lib/test/test_mimetypes.py b/Lib/test/test_mimetypes.py
index f2a19c0863570afe3e8bacb7732fa7e5c410b6a7..b9197069a08a884063fb4334cf0321295debefae 100644 (file)
--- a/Lib/test/test_mimetypes.py
+++ b/Lib/test/test_mimetypes.py
@@ -363,6 +363,22 @@ class MimeTypesTestCase(unittest.TestCase):
         self.assertEqual(self.db.guess_extension(
             type='image/jpg', strict=False), '.jpg')
 
+    def test_added_types_are_used(self):
+        mimetypes.add_type('testing/default-type', '')
+        mime_type, _ = mimetypes.guess_type('')
+        self.assertEqual(mime_type, 'testing/default-type')
+
+        mime_type, _ = mimetypes.guess_type('test.myext')
+        self.assertEqual(mime_type, None)
+
+        mimetypes.add_type('testing/type', '.myext')
+        mime_type, _ = mimetypes.guess_type('test.myext')
+        self.assertEqual(mime_type, 'testing/type')
+
+    def test_add_type_with_undotted_extension_deprecated(self):
+        with self.assertWarns(DeprecationWarning):
+            mimetypes.add_type("testing/type", "undotted")
+
 
 @unittest.skipUnless(sys.platform.startswith("win"), "Windows only")
 class Win32MimeTypesTestCase(unittest.TestCase):

diff --git a/Misc/NEWS.d/next/Library/2019-09-10-09-28-52.gh-issue-75223.VyAJS9.rst b/Misc/NEWS.d/next/Library/2019-09-10-09-28-52.gh-issue-75223.VyAJS9.rst
new file mode 100644 (file)
index 0000000..d3c8d1b
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-09-10-09-28-52.gh-issue-75223.VyAJS9.rst
@@ -0,0 +1,2 @@
+Deprecate undotted extensions in :meth:`mimetypes.MimeTypes.add_type`.
+Patch by Hugo van Kemenade.