[Python-checkins] gh-102947: Improve traceback when calling `fields()` on a non-dataclass (#102948)
AlexWaygood
webhook-mailer at python.org
Thu Mar 23 10:18:04 EDT 2023
https://github.com/python/cpython/commit/baf4eb083c09b323cc12b8636c28c14089b87de8
commit: baf4eb083c09b323cc12b8636c28c14089b87de8
branch: main
author: Alex Waygood <Alex.Waygood at Gmail.com>
committer: AlexWaygood <Alex.Waygood at Gmail.com>
date: 2023-03-23T14:17:54Z
summary:
gh-102947: Improve traceback when calling `fields()` on a non-dataclass (#102948)
files:
A Misc/NEWS.d/next/Library/2023-03-23-13-34-33.gh-issue-102947.cTwcpU.rst
M Lib/dataclasses.py
M Lib/test/test_dataclasses.py
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 82b08fc01788..e3fd0b3e380d 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -1248,7 +1248,7 @@ def fields(class_or_instance):
try:
fields = getattr(class_or_instance, _FIELDS)
except AttributeError:
- raise TypeError('must be called with a dataclass type or instance')
+ raise TypeError('must be called with a dataclass type or instance') from None
# Exclude pseudo-fields. Note that fields is sorted by insertion
# order, so the order of the tuple is as the fields were defined.
diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index 46f33043c270..affd9cede19c 100644
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -5,11 +5,13 @@
from dataclasses import *
import abc
+import io
import pickle
import inspect
import builtins
import types
import weakref
+import traceback
import unittest
from unittest.mock import Mock
from typing import ClassVar, Any, List, Union, Tuple, Dict, Generic, TypeVar, Optional, Protocol, DefaultDict
@@ -1526,6 +1528,16 @@ class C: pass
with self.assertRaisesRegex(TypeError, 'dataclass type or instance'):
fields(C())
+ def test_clean_traceback_from_fields_exception(self):
+ stdout = io.StringIO()
+ try:
+ fields(object)
+ except TypeError as exc:
+ traceback.print_exception(exc, file=stdout)
+ printed_traceback = stdout.getvalue()
+ self.assertNotIn("AttributeError", printed_traceback)
+ self.assertNotIn("__dataclass_fields__", printed_traceback)
+
def test_helper_asdict(self):
# Basic tests for asdict(), it should return a new dictionary.
@dataclass
diff --git a/Misc/NEWS.d/next/Library/2023-03-23-13-34-33.gh-issue-102947.cTwcpU.rst b/Misc/NEWS.d/next/Library/2023-03-23-13-34-33.gh-issue-102947.cTwcpU.rst
new file mode 100644
index 000000000000..b59c98203566
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-03-23-13-34-33.gh-issue-102947.cTwcpU.rst
@@ -0,0 +1,2 @@
+Improve traceback when :func:`dataclasses.fields` is called on a
+non-dataclass. Patch by Alex Waygood
More information about the Python-checkins
mailing list