From 08cc13299413a6398e52ebc5ab5316265a111080 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sat, 26 Oct 2024 00:41:11 -0400
Subject: [PATCH] tests: add test for modern parametrize

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
---
 docs/tutorial.rst  | 35 +++++++++++++++++++++++++++++++++++
 nox/_resolver.py   |  3 +--
 tests/test_main.py |  9 +++++++++
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/docs/tutorial.rst b/docs/tutorial.rst
index 51dfe916..82e61880 100644
--- a/docs/tutorial.rst
+++ b/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
 ----------------------------------------------
 
diff --git a/nox/_resolver.py b/nox/_resolver.py
index e903cd35..c5c2a8e5 100644
--- a/nox/_resolver.py
+++ b/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)
diff --git a/tests/test_main.py b/tests/test_main.py
index 47efe8de..cacafdb6 100644
--- a/tests/test_main.py
+++ b/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(