[Python-checkins] gh-107838: In dataclasses, improve error message when a non-default field follows a default field. (gh-107842)
ericvsmith
webhook-mailer at python.org
Thu Aug 10 10:39:17 EDT 2023
https://github.com/python/cpython/commit/e4275f4df36a7cdd58cd4daa7d65b1947a2593d3
commit: e4275f4df36a7cdd58cd4daa7d65b1947a2593d3
branch: main
author: Eric V. Smith <ericvsmith at users.noreply.github.com>
committer: ericvsmith <ericvsmith at users.noreply.github.com>
date: 2023-08-10T10:39:13-04:00
summary:
gh-107838: In dataclasses, improve error message when a non-default field follows a default field. (gh-107842)
Add the name of the previous default argument field in an error message.
files:
M Lib/dataclasses.py
M Lib/test/test_dataclasses.py
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 3c72c289e4388..21f3fa5c213f1 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -575,15 +575,15 @@ def _init_fn(fields, std_fields, kw_only_fields, frozen, has_post_init,
# message, and future-proofs us in case we build up the function
# using ast.
- seen_default = False
+ seen_default = None
for f in std_fields:
# Only consider the non-kw-only fields in the __init__ call.
if f.init:
if not (f.default is MISSING and f.default_factory is MISSING):
- seen_default = True
+ seen_default = f
elif seen_default:
raise TypeError(f'non-default argument {f.name!r} '
- 'follows default argument')
+ f'follows default argument {seen_default.name!r}')
locals = {f'__dataclass_type_{f.name}__': f.type for f in fields}
locals.update({
diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index 6669f1c57e2e7..bd8d82438414e 100644
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -134,7 +134,7 @@ class C:
# Non-defaults following defaults.
with self.assertRaisesRegex(TypeError,
"non-default argument 'y' follows "
- "default argument"):
+ "default argument 'x'"):
@dataclass
class C:
x: int = 0
@@ -143,7 +143,7 @@ class C:
# A derived class adds a non-default field after a default one.
with self.assertRaisesRegex(TypeError,
"non-default argument 'y' follows "
- "default argument"):
+ "default argument 'x'"):
@dataclass
class B:
x: int = 0
@@ -156,7 +156,7 @@ class C(B):
# a field which didn't use to have a default.
with self.assertRaisesRegex(TypeError,
"non-default argument 'y' follows "
- "default argument"):
+ "default argument 'x'"):
@dataclass
class B:
x: int
@@ -4521,7 +4521,7 @@ class A:
# Make sure we still check for non-kwarg non-defaults not following
# defaults.
- err_regex = "non-default argument 'z' follows default argument"
+ err_regex = "non-default argument 'z' follows default argument 'a'"
with self.assertRaisesRegex(TypeError, err_regex):
@dataclass
class A:
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