bpo-9372: Deprecate several __getitem__ methods (GH-8609)

The __getitem__ methods of DOMEventStream, FileInput,
and FileWrapper classes ignore their 'index' parameters
and return the next item instead.

4 files changed, 42 insertions, 0 deletions

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index d8dabd4..13b60f7 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -89,6 +89,7 @@ __all__ = [
     "requires_IEEE_754", "skip_unless_xattr", "requires_zlib",
     "anticipate_failure", "load_package_tests", "detect_api_mismatch",
     "check__all__", "skip_unless_bind_unix_socket",
+    "ignore_warnings",
     # sys
     "is_jython", "is_android", "check_impl_detail", "unix_shell",
     "setswitchinterval",
@@ -138,6 +139,22 @@ def _ignore_deprecated_imports(ignore=True):
         yield
 
 
+def ignore_warnings(*, category):
+    """Decorator to suppress deprecation warnings.
+
+    Use of context managers to hide warnings make diffs
+    more noisy and tools like 'git blame' less useful.
+    """
+    def decorator(test):
+        @functools.wraps(test)
+        def wrapper(self, *args, **kwargs):
+            with warnings.catch_warnings():
+                warnings.simplefilter('ignore', category=category)
+                return test(self, *args, **kwargs)
+        return wrapper
+    return decorator
+
+
 def import_module(name, deprecated=False, *, required_on=()):
     """Import and return the module to be tested, raising SkipTest if
     it is not available.
diff --git a/Lib/test/test_fileinput.py b/Lib/test/test_fileinput.py
index c97bb4c..c5d722e 100644
--- a/Lib/test/test_fileinput.py
+++ b/Lib/test/test_fileinput.py
@@ -351,6 +351,7 @@ class FileInputTests(BaseTests, unittest.TestCase):
         with FileInput(files=[]) as fi:
             self.assertEqual(fi._files, ('-',))
 
+    @support.ignore_warnings(category=DeprecationWarning)
     def test__getitem__(self):
         """Tests invoking FileInput.__getitem__() with the current
            line number"""
@@ -361,6 +362,14 @@ class FileInputTests(BaseTests, unittest.TestCase):
             retval2 = fi[1]
             self.assertEqual(retval2, "line2\n")
 
+    def test__getitem___deprecation(self):
+        t = self.writeTmp("line1\nline2\n")
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'Use iterator protocol instead'):
+            with FileInput(files=[t]) as fi:
+                self.assertEqual(fi[0], "line1\n")
+
+    @support.ignore_warnings(category=DeprecationWarning)
     def test__getitem__invalid_key(self):
         """Tests invoking FileInput.__getitem__() with an index unequal to
            the line number"""
@@ -370,6 +379,7 @@ class FileInputTests(BaseTests, unittest.TestCase):
                 fi[1]
         self.assertEqual(cm.exception.args, ("accessing lines out of order",))
 
+    @support.ignore_warnings(category=DeprecationWarning)
     def test__getitem__eof(self):
         """Tests invoking FileInput.__getitem__() with the line number but at
            end-of-input"""
diff --git a/Lib/test/test_pulldom.py b/Lib/test/test_pulldom.py
index 3d89e3a..f454098 100644
--- a/Lib/test/test_pulldom.py
+++ b/Lib/test/test_pulldom.py
@@ -159,6 +159,13 @@ class PullDOMTestCase(unittest.TestCase):
             self.fail(
                 "Ran out of events, but should have received END_DOCUMENT")
 
+    def test_getitem_deprecation(self):
+        parser = pulldom.parseString(SMALL_SAMPLE)
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'Use iterator protocol instead'):
+            # This should have returned 'END_ELEMENT'.
+            self.assertEqual(parser[-1][0], pulldom.START_DOCUMENT)
+
 
 class ThoroughTestCase(unittest.TestCase):
     """Test the hard-to-reach parts of pulldom."""
diff --git a/Lib/test/test_wsgiref.py b/Lib/test/test_wsgiref.py
index 8422b30..737dfed 100644
--- a/Lib/test/test_wsgiref.py
+++ b/Lib/test/test_wsgiref.py
@@ -338,6 +338,7 @@ class UtilityTests(TestCase):
         util.setup_testing_defaults(kw)
         self.assertEqual(util.request_uri(kw,query),uri)
 
+    @support.ignore_warnings(category=DeprecationWarning)
     def checkFW(self,text,size,match):
 
         def make_it(text=text,size=size):
@@ -356,6 +357,13 @@ class UtilityTests(TestCase):
         it.close()
         self.assertTrue(it.filelike.closed)
 
+    def test_filewrapper_getitem_deprecation(self):
+        wrapper = util.FileWrapper(StringIO('foobar'), 3)
+        with self.assertWarnsRegex(DeprecationWarning,
+                                   r'Use iterator protocol instead'):
+            # This should have returned 'bar'.
+            self.assertEqual(wrapper[1], 'foo')
+
     def testSimpleShifts(self):
         self.checkShift('','/', '', '/', '')
         self.checkShift('','/x', 'x', '/x', '')