Use nullcontext more as do-nothing context manager.

anntzer · anntzer · commit d7ea24978902 · 2021-04-28T14:00:45.000+02:00
(The implementation of open_file_cm is very close to the second example
in the stdlib docs for nullcontext.)
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -26,7 +26,7 @@
 """
 
 from collections import namedtuple
-from contextlib import contextmanager, suppress
+from contextlib import contextmanager, nullcontext
 from enum import Enum, IntEnum
 import functools
 import importlib
@@ -2286,10 +2286,7 @@ def print_figure(
                     functools.partial(
                         print_method, orientation=orientation)
                 )
-                ctx = (renderer._draw_disabled()
-                       if hasattr(renderer, '_draw_disabled')
-                       else suppress())
-                with ctx:
+                with getattr(renderer, "_draw_disabled", nullcontext)():
                     self.figure.draw(renderer)
 
             if bbox_inches:
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -475,15 +475,10 @@ def to_filehandle(fname, flag='r', return_opened=False, encoding=None):
     return fh
 
 
-@contextlib.contextmanager
 def open_file_cm(path_or_file, mode="r", encoding=None):
     r"""Pass through file objects and context-manage path-likes."""
     fh, opened = to_filehandle(path_or_file, mode, True, encoding)
-    if opened:
-        with fh:
-            yield fh
-    else:
-        yield fh
+    return fh if opened else contextlib.nullcontext(fh)
 
 
 def is_scalar_or_string(val):
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -3089,21 +3089,16 @@ def tight_layout(self, *, pad=1.08, h_pad=None, w_pad=None, rect=None):
         .Figure.set_tight_layout
         .pyplot.tight_layout
         """
-
+        from contextlib import nullcontext
         from .tight_layout import (
             get_subplotspec_list, get_tight_layout_figure)
-        from contextlib import suppress
         subplotspec_list = get_subplotspec_list(self.axes)
         if None in subplotspec_list:
             _api.warn_external("This figure includes Axes that are not "
                                "compatible with tight_layout, so results "
                                "might be incorrect.")
-
         renderer = _get_renderer(self)
-        ctx = (renderer._draw_disabled()
-               if hasattr(renderer, '_draw_disabled')
-               else suppress())
-        with ctx:
+        with getattr(renderer, "_draw_disabled", nullcontext)():
             kwargs = get_tight_layout_figure(
                 self, self.axes, subplotspec_list, renderer,
                 pad=pad, h_pad=h_pad, w_pad=w_pad, rect=rect)
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -1,14 +1,11 @@
 from collections import namedtuple
+from contextlib import nullcontext
 import datetime
 from decimal import Decimal
 import io
 from itertools import product
 import platform
 from types import SimpleNamespace
-try:
-    from contextlib import nullcontext
-except ImportError:
-    from contextlib import ExitStack as nullcontext  # Py3.6.
 
 import dateutil.tz
 
