Fail at parametrize option for empty parameter set

Optionally raise an exception when parametrize collects no arguments.

See: pytest-dev#3849

Author: andrea-cimatoribus-pix4d

src/_pytest/mark/__init__.py

@@ -163,9 +163,9 @@ def pytest_configure(config):
 
     empty_parameterset = config.getini(EMPTY_PARAMETERSET_OPTION)
 
-    if empty_parameterset not in ("skip", "xfail", None, ""):
+    if empty_parameterset not in ("skip", "xfail", "fail_at_parametrize", None, ""):
         raise UsageError(
-            "{!s} must be one of skip and xfail,"
+            "{!s} must be one of skip, xfail or fail_at_parametrize"
             " but it is {!r}".format(EMPTY_PARAMETERSET_OPTION, empty_parameterset)
         )
 

src/_pytest/mark/structures.py

@@ -14,6 +14,11 @@
 EMPTY_PARAMETERSET_OPTION = "empty_parameter_set_mark"
 
 
+class ParametrizeError(Exception):
+
+    """Error collecting arguments in parametrize."""
+
+
 def alias(name, warning=None):
     getter = attrgetter(name)
 
@@ -37,6 +42,8 @@ def get_empty_parameterset_mark(config, argnames, func):
         mark = MARK_GEN.skip
     elif requested_mark == "xfail":
         mark = MARK_GEN.xfail(run=False)
+    elif requested_mark == "fail_at_parametrize":
+        raise ParametrizeError("Empty parameter set")
     else:
         raise LookupError(requested_mark)
     fs, lineno = getfslineno(func)

testing/test_mark.py

@@ -1107,6 +1107,22 @@ def test_parameterset_for_parametrize_marks(testdir, mark):
         assert result_mark.kwargs.get("run") is False
 
 
+def test_parameterset_for_fail_at_parametrize(testdir):
+    testdir.makeini(
+        "[pytest]\n{}={}".format(EMPTY_PARAMETERSET_OPTION, "fail_at_parametrize")
+    )
+
+    config = testdir.parseconfig()
+    from _pytest.mark import pytest_configure, get_empty_parameterset_mark
+    from _pytest.mark.structures import ParametrizeError
+
+    pytest_configure(config)
+
+    with pytest.raises(ParametrizeError) as err:
+        get_empty_parameterset_mark(config, ["a"], all)
+        assert str(err).startswith("Empty parameter set")
+
+
 def test_parameterset_for_parametrize_bad_markname(testdir):
     with pytest.raises(pytest.UsageError):
         test_parameterset_for_parametrize_marks(testdir, "bad")