Small cleanups on _pytest.compat (#5451)

Small cleanups on _pytest.compat

src/_pytest/assertion/util.py

@@ -244,17 +244,9 @@ def _compare_eq_iterable(left, right, verbose=0):
     # dynamic import to speedup pytest
     import difflib
 
-    try:
-        left_formatting = pprint.pformat(left).splitlines()
-        right_formatting = pprint.pformat(right).splitlines()
-        explanation = ["Full diff:"]
-    except Exception:
-        # hack: PrettyPrinter.pformat() in python 2 fails when formatting items that can't be sorted(), ie, calling
-        # sorted() on a list would raise. See issue #718.
-        # As a workaround, the full diff is generated by using the repr() string of each item of each container.
-        left_formatting = sorted(repr(x) for x in left)
-        right_formatting = sorted(repr(x) for x in right)
-        explanation = ["Full diff (fallback to calling repr on each item):"]
+    left_formatting = pprint.pformat(left).splitlines()
+    right_formatting = pprint.pformat(right).splitlines()
+    explanation = ["Full diff:"]
     explanation.extend(
         line.strip() for line in difflib.ndiff(left_formatting, right_formatting)
     )

src/_pytest/compat.py

@@ -10,6 +10,7 @@ from contextlib import contextmanager
 from inspect import Parameter
 from inspect import signature
 
+import attr
 import py
 
 import _pytest
@@ -29,10 +30,6 @@ def _format_args(func):
     return str(signature(func))
 
 
-isfunction = inspect.isfunction
-isclass = inspect.isclass
-# used to work around a python2 exception info leak
-exc_clear = getattr(sys, "exc_clear", lambda: None)
 # The type of re.compile objects is not exposed in Python.
 REGEX_TYPE = type(re.compile(""))
 
@@ -129,11 +126,15 @@ def getfuncargnames(function, is_method=False, cls=None):
     return arg_names
 
 
-@contextmanager
-def dummy_context_manager():
-    """Context manager that does nothing, useful in situations where you might need an actual context manager or not
-    depending on some condition. Using this allow to keep the same code"""
-    yield
+if sys.version_info < (3, 7):
+
+    @contextmanager
+    def nullcontext():
+        yield
+
+
+else:
+    from contextlib import nullcontext  # noqa
 
 
 def get_default_arg_names(function):
@@ -191,6 +192,7 @@ def ascii_escaped(val):
     return _translate_non_printable(ret)
 
 
+@attr.s
 class _PytestWrapper:
     """Dummy wrapper around a function object for internal use only.
 
@@ -199,8 +201,7 @@ class _PytestWrapper:
     to issue warnings when the fixture function is called directly.
     """
 
-    def __init__(self, obj):
-        self.obj = obj
+    obj = attr.ib()
 
 
 def get_real_func(obj):
@@ -280,7 +281,7 @@ def safe_getattr(object, name, default):
 def safe_isclass(obj):
     """Ignore any exception via isinstance on Python 3."""
     try:
-        return isclass(obj)
+        return inspect.isclass(obj)
     except Exception:
         return False
 
@@ -304,8 +305,8 @@ def _setup_collect_fakemodule():
 
     pytest.collect = ModuleType("pytest.collect")
     pytest.collect.__all__ = []  # used for setns
-    for attr in COLLECT_FAKEMODULE_ATTRIBUTES:
-        setattr(pytest.collect, attr, getattr(pytest, attr))
+    for attr_name in COLLECT_FAKEMODULE_ATTRIBUTES:
+        setattr(pytest.collect, attr_name, getattr(pytest, attr_name))
 
 
 class CaptureIO(io.TextIOWrapper):

src/_pytest/fixtures.py

@@ -16,7 +16,6 @@ from _pytest._code.code import FormattedExcinfo
 from _pytest._code.code import TerminalRepr
 from _pytest.compat import _format_args
 from _pytest.compat import _PytestWrapper
-from _pytest.compat import exc_clear
 from _pytest.compat import FuncargnamesCompatAttr
 from _pytest.compat import get_real_func
 from _pytest.compat import get_real_method
@@ -25,7 +24,6 @@ from _pytest.compat import getfuncargnames
 from _pytest.compat import getimfunc
 from _pytest.compat import getlocation
 from _pytest.compat import is_generator
-from _pytest.compat import isclass
 from _pytest.compat import NOTSET
 from _pytest.compat import safe_getattr
 from _pytest.deprecated import FIXTURE_FUNCTION_CALL
@@ -572,10 +570,6 @@ class FixtureRequest(FuncargnamesCompatAttr):
 
         # check if a higher-level scoped fixture accesses a lower level one
         subrequest._check_scope(argname, self.scope, scope)
-
-        # clear sys.exc_info before invoking the fixture (python bug?)
-        # if it's not explicitly cleared it will leak into the call
-        exc_clear()
         try:
             # call the fixture function
             fixturedef.execute(request=subrequest)
@@ -970,7 +964,7 @@ class FixtureFunctionMarker:
     name = attr.ib(default=None)
 
     def __call__(self, function):
-        if isclass(function):
+        if inspect.isclass(function):
             raise ValueError("class fixtures not supported (maybe in the future)")
 
         if getattr(function, "_pytestfixturefunction", False):

src/_pytest/logging.py

@@ -6,7 +6,7 @@ from contextlib import contextmanager
 import py
 
 import pytest
-from _pytest.compat import dummy_context_manager
+from _pytest.compat import nullcontext
 from _pytest.config import create_terminal_writer
 from _pytest.pathlib import Path
 
@@ -436,7 +436,7 @@ class LoggingPlugin:
 
         self.log_cli_handler = None
 
-        self.live_logs_context = lambda: dummy_context_manager()
+        self.live_logs_context = lambda: nullcontext()
         # Note that the lambda for the live_logs_context is needed because
         # live_logs_context can otherwise not be entered multiple times due
         # to limitations of contextlib.contextmanager.
@@ -676,7 +676,7 @@ class _LiveLoggingStreamHandler(logging.StreamHandler):
         ctx_manager = (
             self.capture_manager.global_and_fixture_disabled()
             if self.capture_manager
-            else dummy_context_manager()
+            else nullcontext()
         )
         with ctx_manager:
             if not self._first_record_emitted:

src/_pytest/python.py

@@ -23,8 +23,6 @@ from _pytest.compat import getfslineno
 from _pytest.compat import getimfunc
 from _pytest.compat import getlocation
 from _pytest.compat import is_generator
-from _pytest.compat import isclass
-from _pytest.compat import isfunction
 from _pytest.compat import NOTSET
 from _pytest.compat import REGEX_TYPE
 from _pytest.compat import safe_getattr
@@ -207,7 +205,7 @@ def pytest_pycollect_makeitem(collector, name, obj):
         # We need to try and unwrap the function if it's a functools.partial
         # or a funtools.wrapped.
         # We musn't if it's been wrapped with mock.patch (python 2 only)
-        if not (isfunction(obj) or isfunction(get_real_func(obj))):
+        if not (inspect.isfunction(obj) or inspect.isfunction(get_real_func(obj))):
             filename, lineno = getfslineno(obj)
             warnings.warn_explicit(
                 message=PytestCollectionWarning(
@@ -1172,8 +1170,6 @@ def _idval(val, argname, idx, idfn, item, config):
             # See issue https://github.com/pytest-dev/pytest/issues/2169
             msg = "{}: error raised while trying to determine id of parameter '{}' at position {}\n"
             msg = msg.format(item.nodeid, argname, idx)
-            # we only append the exception type and message because on Python 2 reraise does nothing
-            msg += "  {}: {}\n".format(type(e).__name__, e)
             raise ValueError(msg) from e
     elif config:
         hook_id = config.hook.pytest_make_parametrize_id(
@@ -1190,7 +1186,7 @@ def _idval(val, argname, idx, idfn, item, config):
         return ascii_escaped(val.pattern)
     elif enum is not None and isinstance(val, enum.Enum):
         return str(val)
-    elif (isclass(val) or isfunction(val)) and hasattr(val, "__name__"):
+    elif (inspect.isclass(val) or inspect.isfunction(val)) and hasattr(val, "__name__"):
         return val.__name__
     return str(argname) + str(idx)
 

src/_pytest/python_api.py

@@ -1,3 +1,4 @@
+import inspect
 import math
 import pprint
 import sys
@@ -13,27 +14,12 @@ from more_itertools.more import always_iterable
 
 import _pytest._code
 from _pytest import deprecated
-from _pytest.compat import isclass
 from _pytest.compat import STRING_TYPES
 from _pytest.outcomes import fail
 
 BASE_TYPE = (type, STRING_TYPES)
 
 
-def _cmp_raises_type_error(self, other):
-    """__cmp__ implementation which raises TypeError. Used
-    by Approx base classes to implement only == and != and raise a
-    TypeError for other comparisons.
-
-    Needed in Python 2 only, Python 3 all it takes is not implementing the
-    other operators at all.
-    """
-    __tracebackhide__ = True
-    raise TypeError(
-        "Comparison operators other than == and != not supported by approx objects"
-    )
-
-
 def _non_numeric_type_error(value, at):
     at_str = " at {}".format(at) if at else ""
     return TypeError(
@@ -658,7 +644,9 @@ def raises(expected_exception, *args, **kwargs):
 
     """
     __tracebackhide__ = True
-    for exc in filterfalse(isclass, always_iterable(expected_exception, BASE_TYPE)):
+    for exc in filterfalse(
+        inspect.isclass, always_iterable(expected_exception, BASE_TYPE)
+    ):
         msg = (
             "exceptions must be old-style classes or"
             " derived from BaseException, not %s"

testing/python/metafunc.py

@@ -506,8 +506,8 @@ class TestMetafunc:
         result = testdir.runpytest()
         result.stdout.fnmatch_lines(
             [
-                "*test_foo: error raised while trying to determine id of parameter 'arg' at position 0",
                 "*Exception: bad ids",
+                "*test_foo: error raised while trying to determine id of parameter 'arg' at position 0",
             ]
         )