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bitdancerbitdancer
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Don't use metaclasses when class decorators can do the job.
Thanks to Nick Coghlan for pointing out that I'd forgotten about class decorators.
1 parent 8e0ed33 commit 1be413e

6 files changed

Lines changed: 66 additions & 67 deletions

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‎Lib/email/_policybase.py‎

Lines changed: 20 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -91,31 +91,25 @@ def __add__(self, other):
9191
return self.clone(**other.__dict__)
9292

9393

94-
# Conceptually this isn't a subclass of ABCMeta, but since we want Policy to
95-
# use ABCMeta as a metaclass *and* we want it to use this one as well, we have
96-
# to make this one a subclas of ABCMeta.
97-
class _DocstringExtenderMetaclass(abc.ABCMeta):
98-
99-
def __new__(meta, classname, bases, classdict):
100-
if classdict.get('__doc__') and classdict['__doc__'].startswith('+'):
101-
classdict['__doc__'] = meta._append_doc(bases[0].__doc__,
102-
classdict['__doc__'])
103-
for name, attr in classdict.items():
104-
if attr.__doc__ and attr.__doc__.startswith('+'):
105-
for cls in (cls for base in bases for cls in base.mro()):
106-
doc = getattr(getattr(cls, name), '__doc__')
107-
if doc:
108-
attr.__doc__ = meta._append_doc(doc, attr.__doc__)
109-
break
110-
return super().__new__(meta, classname, bases, classdict)
111-
112-
@staticmethod
113-
def _append_doc(doc, added_doc):
114-
added_doc = added_doc.split('\n', 1)[1]
115-
return doc + '\n' + added_doc
116-
117-
118-
class Policy(_PolicyBase, metaclass=_DocstringExtenderMetaclass):
94+
def _append_doc(doc, added_doc):
95+
doc = doc.rsplit('\n', 1)[0]
96+
added_doc = added_doc.split('\n', 1)[1]
97+
return doc + '\n' + added_doc
98+
99+
def _extend_docstrings(cls):
100+
if cls.__doc__ and cls.__doc__.startswith('+'):
101+
cls.__doc__ = _append_doc(cls.__bases__[0].__doc__, cls.__doc__)
102+
for name, attr in cls.__dict__.items():
103+
if attr.__doc__ and attr.__doc__.startswith('+'):
104+
for c in (c for base in cls.__bases__ for c in base.mro()):
105+
doc = getattr(getattr(c, name), '__doc__')
106+
if doc:
107+
attr.__doc__ = _append_doc(doc, attr.__doc__)
108+
break
109+
return cls
110+
111+
112+
class Policy(_PolicyBase, metaclass=abc.ABCMeta):
119113

120114
r"""Controls for how messages are interpreted and formatted.
121115
@@ -264,6 +258,7 @@ def fold_binary(self, name, value):
264258
raise NotImplementedError
265259

266260

261+
@_extend_docstrings
267262
class Compat32(Policy):
268263

269264
"""+

‎Lib/email/policy.py‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
code that adds all the email6 features.
33
"""
44

5-
from email._policybase import Policy, Compat32, compat32
5+
from email._policybase import Policy, Compat32, compat32, _extend_docstrings
66
from email.utils import _has_surrogates
77
from email.headerregistry import HeaderRegistry as HeaderRegistry
88

@@ -17,6 +17,7 @@
1717
'HTTP',
1818
]
1919

20+
@_extend_docstrings
2021
class EmailPolicy(Policy):
2122

2223
"""+

‎Lib/test/test_email/__init__.py‎

Lines changed: 32 additions & 34 deletions
Original file line numberDiff line numberDiff line change
@@ -73,10 +73,8 @@ def assertDefectsEqual(self, actual, expected):
7373
'item {}'.format(i))
7474

7575

76-
# Metaclass to allow for parameterized tests
77-
class Parameterized(type):
78-
79-
"""Provide a test method parameterization facility.
76+
def parameterize(cls):
77+
"""A test method parameterization class decorator.
8078
8179
Parameters are specified as the value of a class attribute that ends with
8280
the string '_params'. Call the portion before '_params' the prefix. Then
@@ -92,9 +90,10 @@ class Parameterized(type):
9290
In a _params dictioanry, the keys become part of the name of the generated
9391
tests. In a _params list, the values in the list are converted into a
9492
string by joining the string values of the elements of the tuple by '_' and
95-
converting any blanks into '_'s, and this become part of the name. The
96-
full name of a generated test is the portion of the _params name before the
97-
'_params' portion, plus an '_', plus the name derived as explained above.
93+
converting any blanks into '_'s, and this become part of the name.
94+
The full name of a generated test is a 'test_' prefix, the portion of the
95+
test function name after the '_as_' separator, plus an '_', plus the name
96+
derived as explained above.
9897
9998
For example, if we have:
10099
@@ -123,30 +122,29 @@ def example_as_myfunc_input(self, name, count):
123122
be used to select the test individually from the unittest command line.
124123
125124
"""
126-
127-
def __new__(meta, classname, bases, classdict):
128-
paramdicts = {}
129-
for name, attr in classdict.items():
130-
if name.endswith('_params'):
131-
if not hasattr(attr, 'keys'):
132-
d = {}
133-
for x in attr:
134-
if not hasattr(x, '__iter__'):
135-
x = (x,)
136-
n = '_'.join(str(v) for v in x).replace(' ', '_')
137-
d[n] = x
138-
attr = d
139-
paramdicts[name[:-7] + '_as_'] = attr
140-
testfuncs = {}
141-
for name, attr in classdict.items():
142-
for paramsname, paramsdict in paramdicts.items():
143-
if name.startswith(paramsname):
144-
testnameroot = 'test_' + name[len(paramsname):]
145-
for paramname, params in paramsdict.items():
146-
test = (lambda self, name=name, params=params:
147-
getattr(self, name)(*params))
148-
testname = testnameroot + '_' + paramname
149-
test.__name__ = testname
150-
testfuncs[testname] = test
151-
classdict.update(testfuncs)
152-
return super().__new__(meta, classname, bases, classdict)
125+
paramdicts = {}
126+
for name, attr in cls.__dict__.items():
127+
if name.endswith('_params'):
128+
if not hasattr(attr, 'keys'):
129+
d = {}
130+
for x in attr:
131+
if not hasattr(x, '__iter__'):
132+
x = (x,)
133+
n = '_'.join(str(v) for v in x).replace(' ', '_')
134+
d[n] = x
135+
attr = d
136+
paramdicts[name[:-7] + '_as_'] = attr
137+
testfuncs = {}
138+
for name, attr in cls.__dict__.items():
139+
for paramsname, paramsdict in paramdicts.items():
140+
if name.startswith(paramsname):
141+
testnameroot = 'test_' + name[len(paramsname):]
142+
for paramname, params in paramsdict.items():
143+
test = (lambda self, name=name, params=params:
144+
getattr(self, name)(*params))
145+
testname = testnameroot + '_' + paramname
146+
test.__name__ = testname
147+
testfuncs[testname] = test
148+
for key, value in testfuncs.items():
149+
setattr(cls, key, value)
150+
return cls

‎Lib/test/test_email/test_generator.py‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -4,10 +4,11 @@
44
from email import message_from_string, message_from_bytes
55
from email.generator import Generator, BytesGenerator
66
from email import policy
7-
from test.test_email import TestEmailBase, Parameterized
7+
from test.test_email import TestEmailBase, parameterize
88

99

10-
class TestGeneratorBase(metaclass=Parameterized):
10+
@parameterize
11+
class TestGeneratorBase:
1112

1213
policy = policy.default
1314

‎Lib/test/test_email/test_headerregistry.py‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@
44
from email import errors
55
from email import policy
66
from email.message import Message
7-
from test.test_email import TestEmailBase, Parameterized
7+
from test.test_email import TestEmailBase, parameterize
88
from email import headerregistry
99
from email.headerregistry import Address, Group
1010

@@ -175,7 +175,8 @@ def test_set_date_header_from_datetime(self):
175175
self.assertEqual(m['Date'].datetime, self.dt)
176176

177177

178-
class TestAddressHeader(TestHeaderBase, metaclass=Parameterized):
178+
@parameterize
179+
class TestAddressHeader(TestHeaderBase):
179180

180181
example_params = {
181182

‎Lib/test/test_email/test_pickleable.py‎

Lines changed: 6 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -6,9 +6,11 @@
66
import email.message
77
from email import policy
88
from email.headerregistry import HeaderRegistry
9-
from test.test_email import TestEmailBase, Parameterized
9+
from test.test_email import TestEmailBase, parameterize
1010

11-
class TestPickleCopyHeader(TestEmailBase, metaclass=Parameterized):
11+
12+
@parameterize
13+
class TestPickleCopyHeader(TestEmailBase):
1214

1315
header_factory = HeaderRegistry()
1416

@@ -33,7 +35,8 @@ def header_as_pickle(self, name, value):
3335
self.assertEqual(str(h), str(header))
3436

3537

36-
class TestPickleCopyMessage(TestEmailBase, metaclass=Parameterized):
38+
@parameterize
39+
class TestPickleCopyMessage(TestEmailBase):
3740

3841
# Message objects are a sequence, so we have to make them a one-tuple in
3942
# msg_params so they get passed to the parameterized test method as a

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