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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.
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Eric V. Smith 2023-08-10 09:39:13 -05:00 committed by GitHub
parent 37d8b904f8
commit e4275f4df3
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2 changed files with 7 additions and 7 deletions
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6
Lib/dataclasses.py
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@ -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({

8
Lib/test/test_dataclasses.py
View File

@ -134,7 +134,7 @@ class TestCase(unittest.TestCase):
# 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 TestCase(unittest.TestCase):
# 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 TestCase(unittest.TestCase):
# 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 TestKeywordArgs(unittest.TestCase):
# 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: