#2953 show a simple and easy error when keyword expressions trigger a syntax error

_pytest/config.py

@@ -60,8 +60,9 @@ def main(args=None, plugins=None):
             finally:
                 config._ensure_unconfigure()
     except UsageError as e:
+        tw = py.io.TerminalWriter(sys.stderr)
         for msg in e.args:
-            sys.stderr.write("ERROR: %s\n" % (msg,))
+            tw.line("ERROR: {}\n".format(msg), red=True)
         return 4
 
 

_pytest/mark.py

@@ -2,11 +2,14 @@
 from __future__ import absolute_import, division, print_function
 
 import inspect
+import keyword
 import warnings
 import attr
 from collections import namedtuple
 from operator import attrgetter
 from six.moves import map
+
+from _pytest.config import UsageError
 from .deprecated import MARK_PARAMETERSET_UNPACKING
 from .compat import NOTSET, getfslineno
 
@@ -222,6 +225,9 @@ def __getitem__(self, subname):
         return False
 
 
+python_keywords_allowed_list = ["or", "and", "not"]
+
+
 def matchmark(colitem, markexpr):
     """Tries to match on any marker names, attached to the given colitem."""
     return eval(markexpr, {}, MarkMapping.from_keywords(colitem.keywords))
@@ -259,7 +265,13 @@ def matchkeyword(colitem, keywordexpr):
         return mapping[keywordexpr]
     elif keywordexpr.startswith("not ") and " " not in keywordexpr[4:]:
         return not mapping[keywordexpr[4:]]
-    return eval(keywordexpr, {}, mapping)
+    for kwd in keywordexpr.split():
+        if keyword.iskeyword(kwd) and kwd not in python_keywords_allowed_list:
+            raise UsageError("Python keyword '{}' not accepted in expressions passed to '-k'".format(kwd))
+    try:
+        return eval(keywordexpr, {}, mapping)
+    except SyntaxError:
+        raise UsageError("Wrong expression passed to '-k': {}".format(keywordexpr))
 
 
 def pytest_configure(config):

changelog/2953.trivial

@@ -0,0 +1 @@
+Show a simple and easy error when keyword expressions trigger a syntax error (for example, ``"-k foo and import"`` will show an error that you can not use the ``import`` keyword in expressions).

testing/test_mark.py

@@ -344,6 +344,21 @@ def test_func(arg):
     assert list(passed) == list(passed_result)
 
 
+@pytest.mark.parametrize("spec", [
+    ("foo or import", "ERROR: Python keyword 'import' not accepted in expressions passed to '-k'"),
+    ("foo or", "ERROR: Wrong expression passed to '-k': foo or")
+])
+def test_keyword_option_wrong_arguments(spec, testdir, capsys):
+    testdir.makepyfile("""
+            def test_func(arg):
+                pass
+        """)
+    opt, expected_result = spec
+    testdir.inline_run("-k", opt)
+    out = capsys.readouterr().err
+    assert expected_result in out
+
+
 def test_parametrized_collected_from_command_line(testdir):
     """Parametrized test not collected if test named specified
        in command line issue#649.