fix: changelog and update test list

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

docs/changelog/3446.feature.rst

@@ -0,0 +1,3 @@
+Add a ``schema`` command to produce a JSON Schema for tox and the current plugins.
+
+- by :user:`henryiii`

src/tox/session/cmd/schema.py

@@ -6,7 +6,6 @@
 import sys
 import typing
 from pathlib import Path
-from types import NoneType
 from typing import TYPE_CHECKING
 
 import packaging.requirements
@@ -39,7 +38,7 @@ def _process_type(of_type: typing.Any) -> dict[str, typing.Any]:  # noqa: C901,
     }:
         return {"type": "string"}
     if typing.get_origin(of_type) is typing.Union:
-        types = [x for x in typing.get_args(of_type) if x is not NoneType]
+        types = [x for x in typing.get_args(of_type) if x is not type(None)]
         if len(types) == 1:
             return _process_type(types[0])
         msg = f"Union types are not supported: {of_type}"
@@ -95,7 +94,7 @@ def gen_schema(state: State) -> int:
     strict = state.conf.options.strict
 
     # Accessing this adds extra stuff to core, so we need to do it first
-    env_properties = _get_schema(state.envs["3.13"].conf, path="#/properties/env_run_base/properties")
+    env_properties = _get_schema(state.envs["py"].conf, path="#/properties/env_run_base/properties")
 
     properties = _get_schema(core, path="#/properties")
 

tests/config/cli/conftest.py

@@ -12,6 +12,7 @@
 from tox.session.cmd.quickstart import quickstart
 from tox.session.cmd.run.parallel import run_parallel
 from tox.session.cmd.run.sequential import run_sequential
+from tox.session.cmd.schema import gen_schema
 from tox.session.cmd.show_config import show_config
 
 if TYPE_CHECKING:
@@ -23,6 +24,7 @@ def core_handlers() -> dict[str, Callable[[State], int]]:
     return {
         "config": show_config,
         "c": show_config,
+        "schema": gen_schema,
         "list": list_env,
         "l": list_env,
         "run": run_sequential,

tests/session/cmd/test_schema.py

@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+import json
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+    from tox.pytest import MonkeyPatch, ToxProjectCreator
+
+
+def test_show_schema_empty_dir(tox_project: ToxProjectCreator, monkeypatch: MonkeyPatch, tmp_path: Path) -> None:
+    monkeypatch.chdir(tmp_path)
+
+    project = tox_project({})
+    result = project.run("-qq", "schema")
+    schema = json.loads(result.out)
+    assert "properties" in schema
+    assert "tox_root" in schema["properties"]
+