tests: add test for modern parametrize

Signed-off-by: Henry Schreiner <[email protected]>

docs/tutorial.rst

@@ -386,6 +386,41 @@ You can also pass the notified session positional arguments:
 
 Note that this will only have the desired effect if selecting sessions to run via the ``--session/-s`` flag. If you simply run ``nox``, all selected sessions will be run.
 
+Requiring sessions
+------------------
+
+You can also request sessions be run before your session runs. This is done with the ``needs=`` keyword:
+
+
+.. code-block:: python
+
+    @nox.session
+    def tests(session):
+        session.install("pytest")
+        session.run("pytest")
+
+    @nox.session(needs=["tests"])
+    def coverage(session):
+        session.install("coverage")
+        session.run("coverage")
+
+The required sessions will be stably topologically sorted and run. Parametrized
+sessions are supported. You can also get the current Python version with
+``{python}``, though arbitrary parametrizations are not supported.
+
+
+.. code-block:: python
+
+    @nox.session(python=["3.10", "3.13"])
+    def tests(session):
+        session.install("pytest")
+        session.run("pytest")
+
+    @nox.session(python=["3.10", "3.13"], needs=["tests-{python}"])
+    def coverage(session):
+        session.install("coverage")
+        session.run("coverage")
+
 Testing against different and multiple Pythons
 ----------------------------------------------
 

nox/_resolver.py

@@ -192,8 +192,7 @@ def extend_walk(
             walk_list = list(walk)
             cycle = walk_list[walk_list.index(node) :] + [node]
             raise CycleError("Nodes are in a dependency cycle", tuple(cycle))
-        else:
-            walk[node] = None
+        walk[node] = None
         return walk
 
     sort = prepended_by_dependencies(root)

tests/test_main.py

@@ -495,6 +495,8 @@ def test_main_with_bad_session_names(run_nox, session):
         (("g", "a", "d"), ("b", "c", "h", "g", "a", "e", "d")),
         (("m",), ("k-3.9", "k-3.10", "m")),
         (("n",), ("k-3.10", "n")),
+        (("v",), ("u(django='1.9')", "u(django='2.0')", "v")),
+        (("w",), ("u(django='1.9')", "u(django='2.0')", "w")),
     ],
 )
 def test_main_requires(run_nox, sessions, expected_order):
@@ -539,6 +541,13 @@ def test_main_requires_chain_fail(run_nox, session):
     assert "Prerequisite session r was not successful" in stderr
 
 
+@pytest.mark.parametrize("session", ("w", "u"))
+def test_main_requries_modern_param(run_nox, session):
+    noxfile = os.path.join(RESOURCES, "noxfile_requires.py")
+    returncode, _, stderr = run_nox(f"--noxfile={noxfile}", f"--session={session}")
+    assert returncode == 0
+
+
 def test_main_noxfile_options(monkeypatch, generate_noxfile_options):
     noxfile_path = generate_noxfile_options(reuse_existing_virtualenvs=True)
     monkeypatch.setattr(