Allow parametrize to depend on previous parametrize

changelog/13233.feature.rst

@@ -0,0 +1,5 @@
+:hook:`pytest_generate_tests` hooks and :ref:`pytest.mark.parametrize <pytest.mark.parametrize ref>`
+can now depend on previous parametrizations instead of generating a Cartesian product of parameter sets.
+See details in :ref:`parametrize_dependent`.
+
+For example, a :hook:`pytest_generate_tests` hook that relies on marks can now account for all the marks correctly.

doc/en/example/parametrize.rst

@@ -688,3 +688,70 @@ For example:
 In the example above, the first three test cases should run without any
 exceptions, while the fourth should raise a ``ZeroDivisionError`` exception,
 which is expected by pytest.
+
+.. _`parametrize_dependent`:
+
+Adding parameters depending on previous parametrizations
+--------------------------------------------------------------------
+
+By default, :hook:`pytest_generate_tests` hooks and
+:ref:`pytest.mark.parametrize <pytest.mark.parametrize ref>` generate
+a Cartesian product of parameter sets in case of multiple parametrizations,
+see :ref:`parametrize-basics` for some examples.
+
+Sometimes, values of some parameters need to be generated based on values
+of previous parameters or based on their associated marks.
+
+In such cases ``parametrize`` can be passed a callable for ``argvalues``,
+which will decide how to further parametrize each test instance:
+
+.. code-block:: python
+
+    # content of test_parametrize_dependent.py
+    def pytest_generate_tests(metafunc: pytest.Metafunc):
+        if "bar" in metafunc.fixturenames:
+            # parametrize "bar" arg based on "bar_params" mark
+            base_bar_marks = list(metafunc.definition.iter_markers("bar_params"))
+
+            def gen_params(callspec: pytest.CallSpec):
+                # collect all marks
+                bar_marks = base_bar_marks + [
+                    mark for mark in callspec.marks if mark.name == "bar_params"
+                ]
+                # collect all args from all marks
+                return [arg for mark in bar_marks for arg in mark.args]
+
+            metafunc.parametrize("bar", gen_params)
+
+
+    @pytest.mark.bar_params("x")
+    @pytest.mark.parametrize(
+        "foo",
+        [
+            "a",
+            pytest.param("b", marks=[pytest.mark.bar_params("y", "z")]),
+            pytest.param("c", marks=[pytest.mark.bar_params("w")]),
+        ],
+    )
+    def test_function(foo, bar):
+        pass
+
+Running ``pytest`` with verbose mode outputs:
+
+.. code-block:: pytest
+
+    $ pytest -v
+    =========================== test session starts ============================
+    platform linux -- Python 3.x.y, pytest-8.x.y, pluggy-1.x.y -- $PYTHON_PREFIX/bin/python
+    cachedir: .pytest_cache
+    rootdir: /home/sweet/project
+    collecting ... collected 6 items
+
+    test_parametrize_dependent.py::test_function[a-x] PASSED             [ 16%]
+    test_parametrize_dependent.py::test_function[b-x] PASSED             [ 33%]
+    test_parametrize_dependent.py::test_function[b-y] PASSED             [ 50%]
+    test_parametrize_dependent.py::test_function[b-z] PASSED             [ 66%]
+    test_parametrize_dependent.py::test_function[c-x] PASSED             [ 83%]
+    test_parametrize_dependent.py::test_function[c-w] PASSED             [100%]
+
+    ============================ 6 passed in 0.12s =============================

doc/en/reference/reference.rst

@@ -913,6 +913,12 @@ Objects accessible from :ref:`fixtures <fixture>` or :ref:`hooks <hook-reference
 or importable from ``pytest``.
 
 
+CallSpec
+~~~~~~~~
+
+.. autoclass:: pytest.CallSpec()
+    :members:
+
 CallInfo
 ~~~~~~~~
 

src/_pytest/fixtures.py

@@ -77,7 +77,7 @@
 
 
 if TYPE_CHECKING:
-    from _pytest.python import CallSpec2
+    from _pytest.python import CallSpec
     from _pytest.python import Function
     from _pytest.python import Metafunc
 
@@ -184,7 +184,7 @@ def get_parametrized_fixture_argkeys(
     assert scope is not Scope.Function
 
     try:
-        callspec: CallSpec2 = item.callspec  # type: ignore[attr-defined]
+        callspec: CallSpec = item.callspec  # type: ignore[attr-defined]
     except AttributeError:
         return
 

src/_pytest/mark/__init__.py

@@ -19,6 +19,7 @@
 from .structures import MarkDecorator
 from .structures import MarkGenerator
 from .structures import ParameterSet
+from .structures import RawParameterSet
 from _pytest.config import Config
 from _pytest.config import ExitCode
 from _pytest.config import hookimpl
@@ -38,6 +39,7 @@
     "MarkDecorator",
     "MarkGenerator",
     "ParameterSet",
+    "RawParameterSet",
     "get_empty_parameterset_mark",
 ]
 

src/_pytest/mark/structures.py

@@ -32,6 +32,8 @@
 
 
 if TYPE_CHECKING:
+    from typing_extensions import TypeAlias
+
     from ..nodes import Node
 
 
@@ -65,6 +67,9 @@ def get_empty_parameterset_mark(
     return mark
 
 
+RawParameterSet: TypeAlias = "ParameterSet | Sequence[object] | object"
+
+
 class ParameterSet(NamedTuple):
     values: Sequence[object | NotSetType]
     marks: Collection[MarkDecorator | Mark]
@@ -95,7 +100,7 @@ def param(
     @classmethod
     def extract_from(
         cls,
-        parameterset: ParameterSet | Sequence[object] | object,
+        parameterset: RawParameterSet,
         force_tuple: bool = False,
     ) -> ParameterSet:
         """Extract from an object or objects.
@@ -123,7 +128,6 @@ def extract_from(
     @staticmethod
     def _parse_parametrize_args(
         argnames: str | Sequence[str],
-        argvalues: Iterable[ParameterSet | Sequence[object] | object],
         *args,
         **kwargs,
     ) -> tuple[Sequence[str], bool]:
@@ -136,7 +140,7 @@ def _parse_parametrize_args(
 
     @staticmethod
     def _parse_parametrize_parameters(
-        argvalues: Iterable[ParameterSet | Sequence[object] | object],
+        argvalues: Iterable[RawParameterSet],
         force_tuple: bool,
     ) -> list[ParameterSet]:
         return [
@@ -147,12 +151,12 @@ def _parse_parametrize_parameters(
     def _for_parametrize(
         cls,
         argnames: str | Sequence[str],
-        argvalues: Iterable[ParameterSet | Sequence[object] | object],
+        argvalues: Iterable[RawParameterSet],
         func,
         config: Config,
         nodeid: str,
     ) -> tuple[Sequence[str], list[ParameterSet]]:
-        argnames, force_tuple = cls._parse_parametrize_args(argnames, argvalues)
+        argnames, force_tuple = cls._parse_parametrize_args(argnames)
         parameters = cls._parse_parametrize_parameters(argvalues, force_tuple)
         del argvalues
 
@@ -467,7 +471,7 @@ class _ParametrizeMarkDecorator(MarkDecorator):
         def __call__(  # type: ignore[override]
             self,
             argnames: str | Sequence[str],
-            argvalues: Iterable[ParameterSet | Sequence[object] | object],
+            argvalues: Iterable[RawParameterSet],
             *,
             indirect: bool | Sequence[str] = ...,
             ids: Iterable[None | str | float | int | bool]