[Python-checkins] Replace with_traceback() with exception chaining and reraising (GH-32074)

[asvetlov]

https://github.com/python/cpython/commit/a03a09e068435f47d02649dda93988dc44ffaaf1
commit: a03a09e068435f47d02649dda93988dc44ffaaf1
branch: main
author: Oleg Iarygin <oleg at arhadthedev.net>
committer: asvetlov <andrew.svetlov at gmail.com>
date: 2022-03-30T15:28:20+03:00
summary:

Replace with_traceback() with exception chaining and reraising (GH-32074)

files:
A Misc/NEWS.d/next/Library/2022-03-23-13-55-41.bpo-47099.P6quRP.rst
A Misc/NEWS.d/next/Library/2022-03-23-14-16-38.bpo-47099.2raait.rst
M Lib/test/support/socket_helper.py
M Lib/urllib/parse.py
M Lib/urllib/request.py
M Lib/wsgiref/handlers.py

diff --git a/Lib/test/support/socket_helper.py b/Lib/test/support/socket_helper.py
index b51677383ebc5..0ee7a5d69a1b3 100644
--- a/Lib/test/support/socket_helper.py
+++ b/Lib/test/support/socket_helper.py
@@ -256,7 +256,7 @@ def filter_error(err):
                 err = a[0]
             # The error can also be wrapped as args[1]:
             #    except socket.error as msg:
-            #        raise OSError('socket error', msg).with_traceback(sys.exc_info()[2])
+            #        raise OSError('socket error', msg) from msg
             elif len(a) >= 2 and isinstance(a[1], OSError):
                 err = a[1]
             else:
diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py
index 67ba308c409a2..d70a6943f0a73 100644
--- a/Lib/urllib/parse.py
+++ b/Lib/urllib/parse.py
@@ -940,10 +940,9 @@ def urlencode(query, doseq=False, safe='', encoding=None, errors=None,
             # but that's a minor nit.  Since the original implementation
             # allowed empty dicts that type of behavior probably should be
             # preserved for consistency
-        except TypeError:
-            ty, va, tb = sys.exc_info()
+        except TypeError as err:
             raise TypeError("not a valid non-string sequence "
-                            "or mapping object").with_traceback(tb)
+                            "or mapping object") from err
 
     l = []
     if not doseq:
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index 02f96265a8900..84997f268c930 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1579,8 +1579,7 @@ def ftp_open(self, req):
             headers = email.message_from_string(headers)
             return addinfourl(fp, headers, req.full_url)
         except ftplib.all_errors as exp:
-            exc = URLError('ftp error: %r' % exp)
-            raise exc.with_traceback(sys.exc_info()[2])
+            raise URLError(f'ftp error: {exp}') from exp
 
     def connect_ftp(self, user, passwd, host, port, dirs, timeout):
         return ftpwrapper(user, passwd, host, port, dirs, timeout,
@@ -1791,7 +1790,7 @@ def open(self, fullurl, data=None):
         except (HTTPError, URLError):
             raise
         except OSError as msg:
-            raise OSError('socket error', msg).with_traceback(sys.exc_info()[2])
+            raise OSError('socket error', msg) from msg
 
     def open_unknown(self, fullurl, data=None):
         """Overridable interface to open unknown URL type."""
@@ -2093,7 +2092,7 @@ def open_ftp(self, url):
             headers = email.message_from_string(headers)
             return addinfourl(fp, headers, "ftp:" + url)
         except ftperrors() as exp:
-            raise URLError('ftp error %r' % exp).with_traceback(sys.exc_info()[2])
+            raise URLError(f'ftp error: {exp}') from exp
 
     def open_data(self, url, data=None):
         """Use "data" URL."""
@@ -2443,8 +2442,7 @@ def retrfile(self, file, type):
                 conn, retrlen = self.ftp.ntransfercmd(cmd)
             except ftplib.error_perm as reason:
                 if str(reason)[:3] != '550':
-                    raise URLError('ftp error: %r' % reason).with_traceback(
-                        sys.exc_info()[2])
+                    raise URLError(f'ftp error: {reason}') from reason
         if not conn:
             # Set transfer mode to ASCII!
             self.ftp.voidcmd('TYPE A')
diff --git a/Lib/wsgiref/handlers.py b/Lib/wsgiref/handlers.py
index 31360e58785ac..6623b700537cf 100644
--- a/Lib/wsgiref/handlers.py
+++ b/Lib/wsgiref/handlers.py
@@ -228,8 +228,7 @@ def start_response(self, status, headers,exc_info=None):
         if exc_info:
             try:
                 if self.headers_sent:
-                    # Re-raise original exception if headers sent
-                    raise exc_info[0](exc_info[1]).with_traceback(exc_info[2])
+                    raise
             finally:
                 exc_info = None        # avoid dangling circular ref
         elif self.headers is not None:
diff --git a/Misc/NEWS.d/next/Library/2022-03-23-13-55-41.bpo-47099.P6quRP.rst b/Misc/NEWS.d/next/Library/2022-03-23-13-55-41.bpo-47099.P6quRP.rst
new file mode 100644
index 0000000000000..fa2c87e941e8b
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-03-23-13-55-41.bpo-47099.P6quRP.rst
@@ -0,0 +1,3 @@
+Exception chaining is changed from
+:func:`Exception.with_traceback`/:func:`sys.exc_info` to :pep:`3134`.
+Patch by Oleg Iarygin.
diff --git a/Misc/NEWS.d/next/Library/2022-03-23-14-16-38.bpo-47099.2raait.rst b/Misc/NEWS.d/next/Library/2022-03-23-14-16-38.bpo-47099.2raait.rst
new file mode 100644
index 0000000000000..785e53c123f91
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-03-23-14-16-38.bpo-47099.2raait.rst
@@ -0,0 +1,5 @@
+All :exc:`URLError` exception messages raised in
+:class:`urllib.request.URLopener` now contain a colon between ``ftp error``
+and the rest of the message. Previously,
+:func:`~urllib.request.URLopener.open_ftp` missed the colon. Patch by Oleg
+Iarygin.