Fix `pytest.mark.parametrize` when the argvalue is an iterator

changelog/5354.bugfix.rst

@@ -0,0 +1 @@
+Fix ``pytest.mark.parametrize`` when the argvalues is an iterator.

src/_pytest/mark/structures.py

@@ -113,14 +113,18 @@ class ParameterSet(namedtuple("ParameterSet", "values, marks, id")):
             force_tuple = len(argnames) == 1
         else:
             force_tuple = False
-        parameters = [
+        return argnames, force_tuple
+
+    @staticmethod
+    def _parse_parametrize_parameters(argvalues, force_tuple):
+        return [
             ParameterSet.extract_from(x, force_tuple=force_tuple) for x in argvalues
         ]
-        return argnames, parameters
 
     @classmethod
     def _for_parametrize(cls, argnames, argvalues, func, config, function_definition):
-        argnames, parameters = cls._parse_parametrize_args(argnames, argvalues)
+        argnames, force_tuple = cls._parse_parametrize_args(argnames, argvalues)
+        parameters = cls._parse_parametrize_parameters(argvalues, force_tuple)
         del argvalues
 
         if parameters:

testing/test_mark.py

@@ -413,6 +413,28 @@ def test_parametrized_with_kwargs(testdir):
     assert result.ret == 0
 
 
+def test_parametrize_iterator(testdir):
+    """parametrize should work with generators (#5354)."""
+    py_file = testdir.makepyfile(
+        """\
+        import pytest
+
+        def gen():
+            yield 1
+            yield 2
+            yield 3
+
+        @pytest.mark.parametrize('a', gen())
+        def test(a):
+            assert a >= 1
+        """
+    )
+    result = testdir.runpytest(py_file)
+    assert result.ret == 0
+    # should not skip any tests
+    result.stdout.fnmatch_lines(["*3 passed*"])
+
+
 class TestFunctional(object):
     def test_merging_markers_deep(self, testdir):
         # issue 199 - propagate markers into nested classes