added indicative error when parametrizing an argument with a default value

This commit is contained in:
Brian Maissy 2018-04-04 19:44:01 +03:00
parent 36f6687b70
commit 857098fe0f
4 changed files with 33 additions and 7 deletions

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@ -135,6 +135,14 @@ def getfuncargnames(function, is_method=False, cls=None):
return arg_names
def get_default_arg_names(function):
# Note: this code intentionally mirrors the code at the beginning of getfuncargnames,
# to get the arguments which were excluded from its result because they had default values
return tuple(p.name for p in signature(function).parameters.values()
if p.kind in (Parameter.POSITIONAL_OR_KEYWORD, Parameter.KEYWORD_ONLY) and
p.default is not Parameter.empty)
if _PY3:
STRING_TYPES = bytes, str
UNICODE_TYPES = str,

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@ -25,7 +25,7 @@ from _pytest.compat import (
isclass, isfunction, is_generator, ascii_escaped,
REGEX_TYPE, STRING_TYPES, NoneType, NOTSET,
get_real_func, getfslineno, safe_getattr,
safe_str, getlocation, enum,
safe_str, getlocation, enum, get_default_arg_names
)
from _pytest.outcomes import fail
from _pytest.mark.structures import transfer_markers
@ -789,6 +789,7 @@ class Metafunc(fixtures.FuncargnamesCompatAttr):
argnames, parameters = ParameterSet._for_parametrize(
argnames, argvalues, self.function, self.config)
del argvalues
default_arg_names = set(get_default_arg_names(self.function))
if scope is None:
scope = _find_parametrized_scope(argnames, self._arg2fixturedefs, indirect)
@ -797,6 +798,9 @@ class Metafunc(fixtures.FuncargnamesCompatAttr):
valtypes = {}
for arg in argnames:
if arg not in self.fixturenames:
if arg in default_arg_names:
raise ValueError("%r already takes an argument %r with a default value" % (self.function, arg))
else:
if isinstance(indirect, (tuple, list)):
name = 'fixture' if arg in indirect else 'argument'
else:

1
changelog/3221.feature Normal file
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@ -0,0 +1 @@
Added a more indicative error message when parametrizing a function whose argument takes a default value.

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@ -616,6 +616,19 @@ class TestMetafunc(object):
"*uses no argument 'y'*",
])
def test_parametrize_gives_indicative_error_on_function_with_default_argument(self, testdir):
testdir.makepyfile("""
import pytest
@pytest.mark.parametrize('x, y', [('a', 'b')])
def test_simple(x, y=1):
assert len(x) == 1
""")
result = testdir.runpytest("--collect-only")
result.stdout.fnmatch_lines([
"*already takes an argument 'y' with a default value",
])
def test_addcalls_and_parametrize_indirect(self):
def func(x, y):
pass