Calling fixtures directly is now an error instead of a warning

Fix #4545

changelog/4545.removal.rst

@@ -0,0 +1,3 @@
+Calling fixtures directly is now always an error instead of a warning.
+
+See our `docs <https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly>`__ on information on how to update your code.

doc/en/deprecations.rst

@@ -72,46 +72,6 @@ Becomes:
 
 
 
-
-
-Calling fixtures directly
-~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. deprecated:: 3.7
-
-Calling a fixture function directly, as opposed to request them in a test function, is deprecated.
-
-For example:
-
-.. code-block:: python
-
-    @pytest.fixture
-    def cell():
-        return ...
-
-
-    @pytest.fixture
-    def full_cell():
-        cell = cell()
-        cell.make_full()
-        return cell
-
-This is a great source of confusion to new users, which will often call the fixture functions and request them from test functions interchangeably, which breaks the fixture resolution model.
-
-In those cases just request the function directly in the dependent fixture:
-
-.. code-block:: python
-
-    @pytest.fixture
-    def cell():
-        return ...
-
-
-    @pytest.fixture
-    def full_cell(cell):
-        cell.make_full()
-        return cell
-
 ``Node.get_marker``
 ~~~~~~~~~~~~~~~~~~~
 
@@ -353,6 +313,58 @@ By passing a string, users expect that pytest will interpret that command-line u
 on (for example ``bash`` or ``Powershell``), but this is very hard/impossible to do in a portable way.
 
 
+Calling fixtures directly
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+*Removed in version 4.0.*
+
+Calling a fixture function directly, as opposed to request them in a test function, is deprecated.
+
+For example:
+
+.. code-block:: python
+
+    @pytest.fixture
+    def cell():
+        return ...
+
+
+    @pytest.fixture
+    def full_cell():
+        cell = cell()
+        cell.make_full()
+        return cell
+
+This is a great source of confusion to new users, which will often call the fixture functions and request them from test functions interchangeably, which breaks the fixture resolution model.
+
+In those cases just request the function directly in the dependent fixture:
+
+.. code-block:: python
+
+    @pytest.fixture
+    def cell():
+        return ...
+
+
+    @pytest.fixture
+    def full_cell(cell):
+        cell.make_full()
+        return cell
+
+Alternatively if the fixture function is called multiple times inside a test (making it hard to apply the above pattern) or
+if you would like to make minimal changes to the code, you can create a fixture which calls the original function together
+with the ``name`` parameter:
+
+.. code-block:: python
+
+    def cell():
+        return ...
+
+
+    @pytest.fixture(name="cell")
+    def cell_fixture():
+        return cell()
+
 
 ``yield`` tests
 ~~~~~~~~~~~~~~~

src/_pytest/deprecated.py

@@ -20,11 +20,11 @@ from _pytest.warning_types import UnformattedWarning
 YIELD_TESTS = "yield tests were removed in pytest 4.0 - {name} will be ignored"
 
 
-FIXTURE_FUNCTION_CALL = UnformattedWarning(
-    RemovedInPytest4Warning,
-    'Fixture "{name}" called directly. Fixtures are not meant to be called directly, '
-    "are created automatically when test functions request them as parameters. "
-    "See https://docs.pytest.org/en/latest/fixture.html for more information.",
+FIXTURE_FUNCTION_CALL = (
+    'Fixture "{name}" called directly. Fixtures are not meant to be called directly,\n'
+    "but are created automatically when test functions request them as parameters.\n"
+    "See https://docs.pytest.org/en/latest/fixture.html for more information about fixtures, and\n"
+    "https://docs.pytest.org/en/latest/deprecations.html#calling-fixtures-directly about how to update your code."
 )
 
 FIXTURE_NAMED_REQUEST = PytestDeprecationWarning(

src/_pytest/fixtures.py

@@ -942,34 +942,17 @@ def _ensure_immutable_ids(ids):
     return tuple(ids)
 
 
-def wrap_function_to_warning_if_called_directly(function, fixture_marker):
-    """Wrap the given fixture function so we can issue warnings about it being called directly, instead of
-    used as an argument in a test function.
+def wrap_function_to_error_out_if_called_directly(function, fixture_marker):
+    """Wrap the given fixture function so we can raise an error about it being called directly,
+    instead of used as an argument in a test function.
     """
-    is_yield_function = is_generator(function)
-    warning = FIXTURE_FUNCTION_CALL.format(
+    message = FIXTURE_FUNCTION_CALL.format(
         name=fixture_marker.name or function.__name__
     )
 
-    if is_yield_function:
-
-        @functools.wraps(function)
-        def result(*args, **kwargs):
-            __tracebackhide__ = True
-            warnings.warn(warning, stacklevel=3)
-            for x in function(*args, **kwargs):
-                yield x
-
-    else:
-
-        @functools.wraps(function)
-        def result(*args, **kwargs):
-            __tracebackhide__ = True
-            warnings.warn(warning, stacklevel=3)
-            return function(*args, **kwargs)
-
-    if six.PY2:
-        result.__wrapped__ = function
+    @six.wraps(function)
+    def result(*args, **kwargs):
+        fail(message, pytrace=False)
 
     # keep reference to the original function in our own custom attribute so we don't unwrap
     # further than this point and lose useful wrappings like @mock.patch (#3774)
@@ -995,7 +978,7 @@ class FixtureFunctionMarker(object):
                 "fixture is being applied more than once to the same function"
             )
 
-        function = wrap_function_to_warning_if_called_directly(function, self)
+        function = wrap_function_to_error_out_if_called_directly(function, self)
 
         name = self.name or function.__name__
         if name == "request":

testing/deprecated_test.py

@@ -223,17 +223,6 @@ def test_pytest_plugins_in_non_top_level_conftest_deprecated_no_false_positives(
     assert msg not in res.stdout.str()
 
 
-def test_call_fixture_function_deprecated():
-    """Check if a warning is raised if a fixture function is called directly (#3661)"""
-
-    @pytest.fixture
-    def fix():
-        return 1
-
-    with pytest.deprecated_call():
-        assert fix() == 1
-
-
 def test_fixture_named_request(testdir):
     testdir.copy_example()
     result = testdir.runpytest()

testing/python/fixture.py

@@ -3850,3 +3850,14 @@ class TestScopeOrdering(object):
         )
         reprec = testdir.inline_run()
         reprec.assertoutcome(passed=2)
+
+
+def test_call_fixture_function_error():
+    """Check if an error is raised if a fixture function is called directly (#4545)"""
+
+    @pytest.fixture
+    def fix():
+        return 1
+
+    with pytest.raises(pytest.fail.Exception):
+        assert fix() == 1