bpo-36543: Revert "bpo-36543: Remove the xml.etree.cElementTree module." (GH-20117)

* Revert "bpo-36543: Remove the xml.etree.cElementTree module. (GH-19108)"

This reverts commit b33e52511a59c6da7132c226b7f7489b092a33eb.

5 files changed, 21 insertions, 5 deletions

diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst
index 2085a85927..7725e4d158 100644
--- a/Doc/library/xml.etree.elementtree.rst
+++ b/Doc/library/xml.etree.elementtree.rst
@@ -15,6 +15,8 @@ for parsing and creating XML data.
 
 .. versionchanged:: 3.3
    This module will use a fast implementation whenever available.
+
+.. deprecated:: 3.3
    The :mod:`xml.etree.cElementTree` module is deprecated.
 
 
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index b20cd14565..67a83bc958 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -826,11 +826,6 @@ Removed
   module have been removed.  They were deprecated in Python 3.2.
   Use ``iter(x)`` or ``list(x)`` instead of ``x.getchildren()`` and
   ``x.iter()`` or ``list(x.iter())`` instead of ``x.getiterator()``.
-  The ``xml.etree.cElementTree`` module has been removed,
-  use the :mod:`xml.etree.ElementTree` module instead.
-  Since Python 3.3 the ``xml.etree.cElementTree`` module has been deprecated,
-  the ``xml.etree.ElementTree`` module uses a fast implementation whenever
-  available.
   (Contributed by Serhiy Storchaka in :issue:`36543`.)
 
 * The old :mod:`plistlib` API has been removed, it was deprecated since Python
diff --git a/Lib/test/test_xml_etree_c.py b/Lib/test/test_xml_etree_c.py
index 7437e13d06..e26e1714a5 100644
--- a/Lib/test/test_xml_etree_c.py
+++ b/Lib/test/test_xml_etree_c.py
@@ -8,6 +8,9 @@ import unittest
 
 cET = import_fresh_module('xml.etree.ElementTree',
                           fresh=['_elementtree'])
+cET_alias = import_fresh_module('xml.etree.cElementTree',
+                                fresh=['_elementtree', 'xml.etree'],
+                                deprecated=True)
 
 
 @unittest.skipUnless(cET, 'requires _elementtree')
@@ -168,6 +171,14 @@ class MiscTests(unittest.TestCase):
 
 
 @unittest.skipUnless(cET, 'requires _elementtree')
+class TestAliasWorking(unittest.TestCase):
+    # Test that the cET alias module is alive
+    def test_alias_working(self):
+        e = cET_alias.Element('foo')
+        self.assertEqual(e.tag, 'foo')
+
+
+@unittest.skipUnless(cET, 'requires _elementtree')
 @support.cpython_only
 class TestAcceleratorImported(unittest.TestCase):
     # Test that the C accelerator was imported, as expected
@@ -175,6 +186,9 @@ class TestAcceleratorImported(unittest.TestCase):
         # SubElement is a function so it retains _elementtree as its module.
         self.assertEqual(cET.SubElement.__module__, '_elementtree')
 
+    def test_correct_import_cET_alias(self):
+        self.assertEqual(cET_alias.SubElement.__module__, '_elementtree')
+
     def test_parser_comes_from_C(self):
         # The type of methods defined in Python code is types.FunctionType,
         # while the type of methods defined inside _elementtree is
@@ -214,6 +228,7 @@ def test_main():
     # Run the tests specific to the C implementation
     support.run_unittest(
         MiscTests,
+        TestAliasWorking,
         TestAcceleratorImported,
         SizeofTest,
         )
diff --git a/Lib/xml/etree/cElementTree.py b/Lib/xml/etree/cElementTree.py
new file mode 100644
index 0000000000..368e679189
--- /dev/null
+++ b/Lib/xml/etree/cElementTree.py
@@ -0,0 +1,3 @@
+# Deprecated alias for xml.etree.ElementTree
+
+from xml.etree.ElementTree import *
diff --git a/Misc/NEWS.d/next/Library/2020-05-15-21-14-45.bpo-36543.Jt-eSX.rst b/Misc/NEWS.d/next/Library/2020-05-15-21-14-45.bpo-36543.Jt-eSX.rst
new file mode 100644
index 0000000000..468c1ac9ee
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-05-15-21-14-45.bpo-36543.Jt-eSX.rst
@@ -0,0 +1 @@
+Restored the deprecated :mod:`xml.etree.cElementTree` module.