Fix check_no_warnings() docs to reflect what it actually does

Alexey Izbyshev · Alexey Izbyshev · commit 64dfd42ba486 · 2018-09-12T12:51:05.000+03:00
My previous understanding of behavior of check_no_resource_warning(),
which check_no_warnings() is based on, was incorrect.
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
@@ -101,7 +101,8 @@
     # threads
     "threading_setup", "threading_cleanup", "reap_threads", "start_threads",
     # miscellaneous
-    "check_warnings", "check_no_resource_warning", "EnvironmentVarGuard",
+    "check_warnings", "check_no_resource_warning", "check_no_warnings",
+    "EnvironmentVarGuard",
     "run_with_locale", "swap_item",
     "swap_attr", "Matcher", "set_memlimit", "SuppressCrashReport", "sortdict",
     "run_with_tz", "PGO", "missing_compiler_executable", "fd_count",
@@ -1209,10 +1210,14 @@ def check_warnings(*filters, **kwargs):
 
 
 @contextlib.contextmanager
-def check_no_warning(testcase, message='', category=Warning, force_gc=False):
-    """Context manager to check that no matching warning is emitted.
+def check_no_warnings(testcase, message='', category=Warning, force_gc=False):
+    """Context manager to check that no warnings are emitted.
 
-    If force_gc is True, attempt a garbage collection before checking
+    This context manager enables a given warning within its scope
+    and checks that no warnings are emitted even with that warning
+    enabled.
+
+    If force_gc is True, a garbage collection is attempted before checking
     for warnings. This may help to catch warnings emitted when objects
     are deleted, such as ResourceWarning.
 
@@ -1242,7 +1247,7 @@ def check_no_resource_warning(testcase):
     You must remove the object which may emit ResourceWarning before
     the end of the context manager.
     """
-    with check_no_warning(testcase, category=ResourceWarning, force_gc=True):
+    with check_no_warnings(testcase, category=ResourceWarning, force_gc=True):
         yield
 
 
diff --git a/Lib/test/test_file.py b/Lib/test/test_file.py
@@ -182,9 +182,9 @@ def testSetBufferSize(self):
         # make sure that explicitly setting the buffer size doesn't cause
         # misbehaviour especially with repeated close() calls
         for s in (-1, 0, 512):
-            with support.check_no_warning(self,
-                                          message='line buffering',
-                                          category=RuntimeWarning):
+            with support.check_no_warnings(self,
+                                           message='line buffering',
+                                           category=RuntimeWarning):
                 self._checkBufferSize(s)
 
         # test that attempts to use line buffering in binary mode cause
