bpo-45171: Fix stacklevel handling in logging. (GH-28287)

Lib/logging/__init__.py

@@ -159,8 +159,8 @@ def addLevelName(level, levelName):
     finally:
         _releaseLock()
 
-if hasattr(sys, '_getframe'):
-    currentframe = lambda: sys._getframe(3)
+if hasattr(sys, "_getframe"):
+    currentframe = lambda: sys._getframe(1)
 else: #pragma: no cover
     def currentframe():
         """Return the frame object for the caller's stack frame."""
@@ -184,13 +184,18 @@ else: #pragma: no cover
 _srcfile = os.path.normcase(addLevelName.__code__.co_filename)
 
 # _srcfile is only used in conjunction with sys._getframe().
-# To provide compatibility with older versions of Python, set _srcfile
-# to None if _getframe() is not available; this value will prevent
-# findCaller() from being called. You can also do this if you want to avoid
-# the overhead of fetching caller information, even when _getframe() is
-# available.
-#if not hasattr(sys, '_getframe'):
-#    _srcfile = None
+# Setting _srcfile to None will prevent findCaller() from being called. This
+# way, you can avoid the overhead of fetching caller information.
+
+# The following is based on warnings._is_internal_frame. It makes sure that
+# frames of the import mechanism are skipped when logging at module level and
+# using a stacklevel value greater than one.
+def _is_internal_frame(frame):
+    """Signal whether the frame is a CPython or logging module internal."""
+    filename = os.path.normcase(frame.f_code.co_filename)
+    return filename == _srcfile or (
+        "importlib" in filename and "_bootstrap" in filename
+    )
 
 
 def _checkLevel(level):
@@ -1558,33 +1563,31 @@ class Logger(Filterer):
         f = currentframe()
         #On some versions of IronPython, currentframe() returns None if
         #IronPython isn't run with -X:Frames.
-        if f is not None:
-            f = f.f_back
-        orig_f = f
-        while f and stacklevel > 1:
-            f = f.f_back
-            stacklevel -= 1
-        if not f:
-            f = orig_f
-        rv = "(unknown file)", 0, "(unknown function)", None
-        while hasattr(f, "f_code"):
-            co = f.f_code
-            filename = os.path.normcase(co.co_filename)
-            if filename == _srcfile:
-                f = f.f_back
-                continue
-            sinfo = None
-            if stack_info:
-                sio = io.StringIO()
-                sio.write('Stack (most recent call last):\n')
+        if f is None:
+            return "(unknown file)", 0, "(unknown function)", None
+        while stacklevel > 0:
+            next_f = f.f_back
+            if next_f is None:
+                ##TODO: We've got options here
+                ## If we want to use the last (deepest) frame:
+                break
+                ## If we want to mimic the warnings module:
+                #return ("sys", 1, "(unknown function)", None)
+                ## If we want to be pedantic:
+                #raise ValueError("call stack is not deep enough")
+            f = next_f
+            if not _is_internal_frame(f):
+                stacklevel -= 1
+        co = f.f_code
+        sinfo = None
+        if stack_info:
+            with io.StringIO() as sio:
+                sio.write("Stack (most recent call last):\n")
                 traceback.print_stack(f, file=sio)
                 sinfo = sio.getvalue()
                 if sinfo[-1] == '\n':
                     sinfo = sinfo[:-1]
-                sio.close()
-            rv = (co.co_filename, f.f_lineno, co.co_name, sinfo)
-            break
-        return rv
+        return co.co_filename, f.f_lineno, co.co_name, sinfo
 
     def makeRecord(self, name, level, fn, lno, msg, args, exc_info,
                    func=None, extra=None, sinfo=None):

Lib/test/test_logging.py

@@ -5050,9 +5050,10 @@ class LoggerTest(BaseTest, AssertErrorMessage):
 
     def test_find_caller_with_stacklevel(self):
         the_level = 1
+        trigger = self.logger.warning
 
         def innermost():
-            self.logger.warning('test', stacklevel=the_level)
+            trigger('test', stacklevel=the_level)
 
         def inner():
             innermost()
@@ -5074,6 +5075,16 @@ class LoggerTest(BaseTest, AssertErrorMessage):
         self.assertEqual(records[-1].funcName, 'outer')
         self.assertGreater(records[-1].lineno, lineno)
         lineno = records[-1].lineno
+        trigger = self.logger.warn
+        outer()
+        self.assertEqual(records[-1].funcName, 'outer')
+        root_logger = logging.getLogger()
+        root_logger.addHandler(self.recording)
+        trigger = logging.warning
+        outer()
+        self.assertEqual(records[-1].funcName, 'outer')
+        root_logger.removeHandler(self.recording)
+        trigger = self.logger.warning
         the_level += 1
         outer()
         self.assertEqual(records[-1].funcName, 'test_find_caller_with_stacklevel')

Misc/NEWS.d/next/Library/2021-09-11-16-06-54.bpo-45171.ec597j.rst

@@ -0,0 +1,4 @@
+Fix handling of the ``stacklevel`` argument to logging functions in the
+:mod:`logging` module so that it is consistent accross all logging functions
+and, as advertised, similar to the ``stacklevel`` argument used in
+:meth:`~warnings.warn`.