Fix onlyif_cmds_exist skip message

IPython/testing/decorators.py

@@ -1,399 +1,399 b''
 # -*- coding: utf-8 -*-
 """Decorators for labeling test objects.
 
 Decorators that merely return a modified version of the original function
 object are straightforward.  Decorators that return a new function object need
 to use nose.tools.make_decorator(original_function)(decorator) in returning the
 decorator, in order to preserve metadata such as function name, setup and
 teardown functions and so on - see nose.tools for more information.
 
 This module provides a set of useful decorators meant to be ready to use in
 your own tests.  See the bottom of the file for the ready-made ones, and if you
 find yourself writing a new one that may be of generic use, add it here.
 
 Included decorators:
 
 
 Lightweight testing that remains unittest-compatible.
 
 - An @as_unittest decorator can be used to tag any normal parameter-less
   function as a unittest TestCase.  Then, both nose and normal unittest will
   recognize it as such.  This will make it easier to migrate away from Nose if
   we ever need/want to while maintaining very lightweight tests.
 
 NOTE: This file contains IPython-specific decorators. Using the machinery in
 IPython.external.decorators, we import either numpy.testing.decorators if numpy is
 available, OR use equivalent code in IPython.external._decorators, which
 we've copied verbatim from numpy.
 
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import os
 import shutil
 import sys
 import tempfile
 import unittest
 import warnings
 from importlib import import_module
 
 from decorator import decorator
 
 # Expose the unittest-driven decorators
 from .ipunittest import ipdoctest, ipdocstring
 
 # Grab the numpy-specific decorators which we keep in a file that we
 # occasionally update from upstream: decorators.py is a copy of
 # numpy.testing.decorators, we expose all of it here.
 from IPython.external.decorators import knownfailureif
 
 #-----------------------------------------------------------------------------
 # Classes and functions
 #-----------------------------------------------------------------------------
 
 # Simple example of the basic idea
 def as_unittest(func):
     """Decorator to make a simple function into a normal test via unittest."""
     class Tester(unittest.TestCase):
         def test(self):
             func()
 
     Tester.__name__ = func.__name__
 
     return Tester
 
 # Utility functions
 
 def apply_wrapper(wrapper, func):
     """Apply a wrapper to a function for decoration.
 
     This mixes Michele Simionato's decorator tool with nose's make_decorator,
     to apply a wrapper in a decorator so that all nose attributes, as well as
     function signature and other properties, survive the decoration cleanly.
     This will ensure that wrapped functions can still be well introspected via
     IPython, for example.
     """
     warnings.warn("The function `apply_wrapper` is deprecated since IPython 4.0",
             DeprecationWarning, stacklevel=2)
     import nose.tools
 
     return decorator(wrapper,nose.tools.make_decorator(func)(wrapper))
 
 
 def make_label_dec(label, ds=None):
     """Factory function to create a decorator that applies one or more labels.
 
     Parameters
     ----------
       label : string or sequence
       One or more labels that will be applied by the decorator to the functions
     it decorates.  Labels are attributes of the decorated function with their
     value set to True.
 
       ds : string
       An optional docstring for the resulting decorator.  If not given, a
       default docstring is auto-generated.
 
     Returns
     -------
       A decorator.
 
     Examples
     --------
 
     A simple labeling decorator:
 
     >>> slow = make_label_dec('slow')
     >>> slow.__doc__
     "Labels a test as 'slow'."
 
     And one that uses multiple labels and a custom docstring:
 
     >>> rare = make_label_dec(['slow','hard'],
     ... "Mix labels 'slow' and 'hard' for rare tests.")
     >>> rare.__doc__
     "Mix labels 'slow' and 'hard' for rare tests."
 
     Now, let's test using this one:
     >>> @rare
     ... def f(): pass
     ...
     >>>
     >>> f.slow
     True
     >>> f.hard
     True
     """
 
     warnings.warn("The function `make_label_dec` is deprecated since IPython 4.0",
             DeprecationWarning, stacklevel=2)
     if isinstance(label, str):
         labels = [label]
     else:
         labels = label
 
     # Validate that the given label(s) are OK for use in setattr() by doing a
     # dry run on a dummy function.
     tmp = lambda : None
     for label in labels:
         setattr(tmp,label,True)
 
     # This is the actual decorator we'll return
     def decor(f):
         for label in labels:
             setattr(f,label,True)
         return f
 
     # Apply the user's docstring, or autogenerate a basic one
     if ds is None:
         ds = "Labels a test as %r." % label
     decor.__doc__ = ds
 
     return decor
 
 
 def skip_iptest_but_not_pytest(f):
     """
     Warning this will make the test invisible to iptest.
     """
     import os
 
     if os.environ.get("IPTEST_WORKING_DIR", None) is not None:
         f.__test__ = False
     return f
 
 
 # Inspired by numpy's skipif, but uses the full apply_wrapper utility to
 # preserve function metadata better and allows the skip condition to be a
 # callable.
 def skipif(skip_condition, msg=None):
     ''' Make function raise SkipTest exception if skip_condition is true
 
     Parameters
     ----------
 
     skip_condition : bool or callable
       Flag to determine whether to skip test. If the condition is a
       callable, it is used at runtime to dynamically make the decision. This
       is useful for tests that may require costly imports, to delay the cost
       until the test suite is actually executed.
     msg : string
       Message to give on raising a SkipTest exception.
 
     Returns
     -------
     decorator : function
       Decorator, which, when applied to a function, causes SkipTest
       to be raised when the skip_condition was True, and the function
       to be called normally otherwise.
 
     Notes
     -----
     You will see from the code that we had to further decorate the
     decorator with the nose.tools.make_decorator function in order to
     transmit function name, and various other metadata.
     '''
 
     def skip_decorator(f):
         # Local import to avoid a hard nose dependency and only incur the
         # import time overhead at actual test-time.
         import nose
 
         # Allow for both boolean or callable skip conditions.
         if callable(skip_condition):
             skip_val = skip_condition
         else:
             skip_val = lambda : skip_condition
 
         def get_msg(func,msg=None):
             """Skip message with information about function being skipped."""
             if msg is None: out = 'Test skipped due to test condition.'
             else: out = msg
             return "Skipping test: %s. %s" % (func.__name__,out)
 
         # We need to define *two* skippers because Python doesn't allow both
         # return with value and yield inside the same function.
         def skipper_func(*args, **kwargs):
             """Skipper for normal test functions."""
             if skip_val():
                 raise nose.SkipTest(get_msg(f,msg))
             else:
                 return f(*args, **kwargs)
 
         def skipper_gen(*args, **kwargs):
             """Skipper for test generators."""
             if skip_val():
                 raise nose.SkipTest(get_msg(f,msg))
             else:
                 for x in f(*args, **kwargs):
                     yield x
 
         # Choose the right skipper to use when building the actual generator.
         if nose.util.isgenerator(f):
             skipper = skipper_gen
         else:
             skipper = skipper_func
 
         return nose.tools.make_decorator(f)(skipper)
 
     return skip_decorator
 
 # A version with the condition set to true, common case just to attach a message
 # to a skip decorator
 def skip(msg=None):
     """Decorator factory - mark a test function for skipping from test suite.
 
     Parameters
     ----------
       msg : string
         Optional message to be added.
 
     Returns
     -------
        decorator : function
          Decorator, which, when applied to a function, causes SkipTest
          to be raised, with the optional message added.
       """
     if msg and not isinstance(msg, str):
         raise ValueError('invalid object passed to `@skip` decorator, did you '
                          'meant `@skip()` with brackets ?')
     return skipif(True, msg)
 
 
 def onlyif(condition, msg):
     """The reverse from skipif, see skipif for details."""
 
     if callable(condition):
         skip_condition = lambda : not condition()
     else:
         skip_condition = lambda : not condition
 
     return skipif(skip_condition, msg)
 
 #-----------------------------------------------------------------------------
 # Utility functions for decorators
 def module_not_available(module):
     """Can module be imported?  Returns true if module does NOT import.
 
     This is used to make a decorator to skip tests that require module to be
     available, but delay the 'import numpy' to test execution time.
     """
     try:
         mod = import_module(module)
         mod_not_avail = False
     except ImportError:
         mod_not_avail = True
 
     return mod_not_avail
 
 
 def decorated_dummy(dec, name):
     """Return a dummy function decorated with dec, with the given name.
 
     Examples
     --------
     import IPython.testing.decorators as dec
     setup = dec.decorated_dummy(dec.skip_if_no_x11, __name__)
     """
     warnings.warn("The function `decorated_dummy` is deprecated since IPython 4.0",
         DeprecationWarning, stacklevel=2)
     dummy = lambda: None
     dummy.__name__ = name
     return dec(dummy)
 
 #-----------------------------------------------------------------------------
 # Decorators for public use
 
 # Decorators to skip certain tests on specific platforms.
 skip_win32 = skipif(sys.platform == 'win32',
                     "This test does not run under Windows")
 skip_linux = skipif(sys.platform.startswith('linux'),
                     "This test does not run under Linux")
 skip_osx = skipif(sys.platform == 'darwin',"This test does not run under OS X")
 
 
 # Decorators to skip tests if not on specific platforms.
 skip_if_not_win32 = skipif(sys.platform != 'win32',
                            "This test only runs under Windows")
 skip_if_not_linux = skipif(not sys.platform.startswith('linux'),
                            "This test only runs under Linux")
 skip_if_not_osx = skipif(sys.platform != 'darwin',
                          "This test only runs under OSX")
 
 
 _x11_skip_cond = (sys.platform not in ('darwin', 'win32') and
                   os.environ.get('DISPLAY', '') == '')
 _x11_skip_msg = "Skipped under *nix when X11/XOrg not available"
 
 skip_if_no_x11 = skipif(_x11_skip_cond, _x11_skip_msg)
 
 
 # Decorators to skip certain tests on specific platform/python combinations
 skip_win32_py38 = skipif(sys.version_info > (3,8) and os.name == 'nt')
 
 
 # not a decorator itself, returns a dummy function to be used as setup
 def skip_file_no_x11(name):
     warnings.warn("The function `skip_file_no_x11` is deprecated since IPython 4.0",
             DeprecationWarning, stacklevel=2)
     return decorated_dummy(skip_if_no_x11, name) if _x11_skip_cond else None
 
 # Other skip decorators
 
 # generic skip without module
 skip_without = lambda mod: skipif(module_not_available(mod), "This test requires %s" % mod)
 
 skipif_not_numpy = skip_without('numpy')
 
 skipif_not_matplotlib = skip_without('matplotlib')
 
 skipif_not_sympy = skip_without('sympy')
 
 skip_known_failure = knownfailureif(True,'This test is known to fail')
 
 # A null 'decorator', useful to make more readable code that needs to pick
 # between different decorators based on OS or other conditions
 null_deco = lambda f: f
 
 # Some tests only run where we can use unicode paths. Note that we can't just
 # check os.path.supports_unicode_filenames, which is always False on Linux.
 try:
     f = tempfile.NamedTemporaryFile(prefix=u"tmp€")
 except UnicodeEncodeError:
     unicode_paths = False
 else:
     unicode_paths = True
     f.close()
 
 onlyif_unicode_paths = onlyif(unicode_paths, ("This test is only applicable "
                                     "where we can use unicode in filenames."))
 
 
 def onlyif_cmds_exist(*commands):
     """
     Decorator to skip test when at least one of `commands` is not found.
     """
     for cmd in commands:
-        reason = "This test runs only if command '{cmd}' is installed"
+        reason = f"This test runs only if command '{cmd}' is installed"
         if not shutil.which(cmd):
             if os.environ.get("IPTEST_WORKING_DIR", None) is not None:
                 return skip(reason)
             else:
                 import pytest
 
                 return pytest.mark.skip(reason=reason)
     return null_deco
 
 def onlyif_any_cmd_exists(*commands):
     """
     Decorator to skip test unless at least one of `commands` is found.
     """
     warnings.warn("The function `onlyif_any_cmd_exists` is deprecated since IPython 4.0",
             DeprecationWarning, stacklevel=2)
     for cmd in commands:
         if shutil.which(cmd):
             return null_deco
     return skip("This test runs only if one of the commands {0} "
                 "is installed".format(commands))