Remove _pytest.compat.is_generator() fixes #12960

changelog/12960.breaking.rst

@@ -0,0 +1,3 @@
+Test functions containing a yield now cause an explicit error. They have not been run since pytest 4.0, and were previously marked as an expected failure and deprecation warning.
+
+See :ref:`the docs <yield tests deprecated>` for more information.

doc/en/deprecations.rst

@@ -374,6 +374,42 @@ an appropriate period of deprecation has passed.
 
 Some breaking changes which could not be deprecated are also listed.
 
+.. _yield tests deprecated:
+
+``yield`` tests
+~~~~~~~~~~~~~~~
+
+.. versionremoved:: 4.0
+
+    ``yield`` tests ``xfail``.
+
+.. versionremoved:: 8.4
+
+    ``yield`` tests raise a collection error.
+
+pytest no longer supports ``yield``-style tests, where a test function actually ``yield`` functions and values
+that are then turned into proper test methods. Example:
+
+.. code-block:: python
+
+    def check(x, y):
+        assert x**x == y
+
+
+    def test_squared():
+        yield check, 2, 4
+        yield check, 3, 9
+
+This would result in two actual test functions being generated.
+
+This form of test function doesn't support fixtures properly, and users should switch to ``pytest.mark.parametrize``:
+
+.. code-block:: python
+
+    @pytest.mark.parametrize("x, y", [(2, 4), (3, 9)])
+    def test_squared(x, y):
+        assert x**x == y
+
 .. _nose-deprecation:
 
 Support for tests written for nose
@@ -1270,36 +1306,6 @@ with the ``name`` parameter:
         return cell()
 
 
-.. _yield tests deprecated:
-
-``yield`` tests
-~~~~~~~~~~~~~~~
-
-.. versionremoved:: 4.0
-
-pytest supported ``yield``-style tests, where a test function actually ``yield`` functions and values
-that are then turned into proper test methods. Example:
-
-.. code-block:: python
-
-    def check(x, y):
-        assert x**x == y
-
-
-    def test_squared():
-        yield check, 2, 4
-        yield check, 3, 9
-
-This would result into two actual test functions being generated.
-
-This form of test function doesn't support fixtures properly, and users should switch to ``pytest.mark.parametrize``:
-
-.. code-block:: python
-
-    @pytest.mark.parametrize("x, y", [(2, 4), (3, 9)])
-    def test_squared(x, y):
-        assert x**x == y
-
 .. _internal classes accessed through node deprecated:
 
 Internal classes accessed through ``Node``

src/_pytest/compat.py

@@ -43,11 +43,6 @@ class NotSetType(enum.Enum):
 # fmt: on
 
 
-def is_generator(func: object) -> bool:
-    genfunc = inspect.isgeneratorfunction(func)
-    return genfunc and not iscoroutinefunction(func)
-
-
 def iscoroutinefunction(func: object) -> bool:
     """Return True if func is a coroutine function (a function defined with async
     def syntax, and doesn't contain yield), or a function decorated with

src/_pytest/fixtures.py

@@ -49,7 +49,6 @@
 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 NOTSET
 from _pytest.compat import NotSetType
 from _pytest.compat import safe_getattr
@@ -893,7 +892,7 @@ def toterminal(self, tw: TerminalWriter) -> None:
 def call_fixture_func(
     fixturefunc: _FixtureFunc[FixtureValue], request: FixtureRequest, kwargs
 ) -> FixtureValue:
-    if is_generator(fixturefunc):
+    if inspect.isgeneratorfunction(fixturefunc):
         fixturefunc = cast(
             Callable[..., Generator[FixtureValue, None, None]], fixturefunc
         )

src/_pytest/python.py

@@ -43,7 +43,6 @@
 from _pytest.compat import get_real_func
 from _pytest.compat import getimfunc
 from _pytest.compat import is_async_function
-from _pytest.compat import is_generator
 from _pytest.compat import LEGACY_PATH
 from _pytest.compat import NOTSET
 from _pytest.compat import safe_getattr
@@ -57,7 +56,6 @@
 from _pytest.fixtures import FuncFixtureInfo
 from _pytest.fixtures import get_scope_node
 from _pytest.main import Session
-from _pytest.mark import MARK_GEN
 from _pytest.mark import ParameterSet
 from _pytest.mark.structures import get_unpacked_marks
 from _pytest.mark.structures import Mark
@@ -231,16 +229,13 @@
                 lineno=lineno + 1,
             )
         elif getattr(obj, "__test__", True):
-            if is_generator(obj):
-                res = Function.from_parent(collector, name=name)
-                reason = (
-                    f"yield tests were removed in pytest 4.0 - {name} will be ignored"
+            if inspect.isgeneratorfunction(obj):
+                fail(
+                    f"'yield' keyword is allowed in fixtures, but not in tests ({name})",
+                    pytrace=False,
                 )
-                res.add_marker(MARK_GEN.xfail(run=False, reason=reason))
-                res.warn(PytestCollectionWarning(reason))
-                return res
-            else:
-                return list(collector._genfunctions(name, obj))
+            return list(collector._genfunctions(name, obj))
+        return None
     return None
 
 

testing/test_collection.py

@@ -1878,3 +1878,20 @@ def test_respect_system_exceptions(
     result.stdout.fnmatch_lines([f"*{head}*"])
     result.stdout.fnmatch_lines([msg])
     result.stdout.no_fnmatch_line(f"*{tail}*")
+
+
+def test_yield_disallowed_in_tests(pytester: Pytester):
+    """Ensure generator test functions with 'yield' fail collection (#12960)."""
+    pytester.makepyfile(
+        """
+        def test_with_yield():
+            yield 1
+        """
+    )
+    result = pytester.runpytest()
+    assert result.ret == 2
+    result.stdout.fnmatch_lines(
+        ["*'yield' keyword is allowed in fixtures, but not in tests (test_with_yield)*"]
+    )
+    # Assert that no tests were collected
+    result.stdout.fnmatch_lines(["*collected 0 items*"])

testing/test_compat.py

@@ -5,35 +5,21 @@
 from functools import cached_property
 from functools import partial
 from functools import wraps
-import sys
 from typing import TYPE_CHECKING
 
 from _pytest.compat import _PytestWrapper
 from _pytest.compat import assert_never
 from _pytest.compat import get_real_func
-from _pytest.compat import is_generator
 from _pytest.compat import safe_getattr
 from _pytest.compat import safe_isclass
 from _pytest.outcomes import OutcomeException
-from _pytest.pytester import Pytester
 import pytest
 
 
 if TYPE_CHECKING:
     from typing_extensions import Literal
 
 
-def test_is_generator() -> None:
-    def zap():
-        yield  # pragma: no cover
-
-    def foo():
-        pass  # pragma: no cover
-
-    assert is_generator(zap)
-    assert not is_generator(foo)
-
-
 def test_real_func_loop_limit() -> None:
     class Evil:
         def __init__(self):
@@ -95,65 +81,6 @@ def foo(x):
     assert get_real_func(partial(foo)) is foo
 
 
-@pytest.mark.skipif(sys.version_info >= (3, 11), reason="coroutine removed")
-def test_is_generator_asyncio(pytester: Pytester) -> None:
-    pytester.makepyfile(
-        """
-        from _pytest.compat import is_generator
-        import asyncio
-        @asyncio.coroutine
-        def baz():
-            yield from [1,2,3]
-
-        def test_is_generator_asyncio():
-            assert not is_generator(baz)
-    """
-    )
-    # avoid importing asyncio into pytest's own process,
-    # which in turn imports logging (#8)
-    result = pytester.runpytest_subprocess()
-    result.stdout.fnmatch_lines(["*1 passed*"])
-
-
-def test_is_generator_async_syntax(pytester: Pytester) -> None:
-    pytester.makepyfile(
-        """
-        from _pytest.compat import is_generator
-        def test_is_generator_py35():
-            async def foo():
-                await foo()
-
-            async def bar():
-                pass
-
-            assert not is_generator(foo)
-            assert not is_generator(bar)
-    """
-    )
-    result = pytester.runpytest()
-    result.stdout.fnmatch_lines(["*1 passed*"])
-
-
-def test_is_generator_async_gen_syntax(pytester: Pytester) -> None:
-    pytester.makepyfile(
-        """
-        from _pytest.compat import is_generator
-        def test_is_generator():
-            async def foo():
-                yield
-                await foo()
-
-            async def bar():
-                yield
-
-            assert not is_generator(foo)
-            assert not is_generator(bar)
-    """
-    )
-    result = pytester.runpytest()
-    result.stdout.fnmatch_lines(["*1 passed*"])
-
-
 class ErrorsHelper:
     @property
     def raise_baseexception(self):

testing/test_terminal.py

@@ -1042,10 +1042,6 @@ def test_pass():
             class TestClass(object):
                 def test_skip(self):
                     pytest.skip("hello")
-            def test_gen():
-                def check(x):
-                    assert x == 1
-                yield check, 0
         """
         )
 
@@ -1058,7 +1054,6 @@ def test_verbose_reporting(self, verbose_testfile, pytester: Pytester) -> None:
                 "*test_verbose_reporting.py::test_fail *FAIL*",
                 "*test_verbose_reporting.py::test_pass *PASS*",
                 "*test_verbose_reporting.py::TestClass::test_skip *SKIP*",
-                "*test_verbose_reporting.py::test_gen *XFAIL*",
             ]
         )
         assert result.ret == 1