tox --showconfig -e py shows core configs (#2625)

Resolves #2624

docs/changelog/2624.bugfix.rst

@@ -0,0 +1 @@
+``tox --showconfig -e py311`` reports tox section, though it should not - by :user:`gaborbernat`.

src/tox/session/cmd/legacy.py

@@ -91,7 +91,7 @@ def legacy(state: State) -> int:
     option = state.conf.options
     if option.show_config:
         option.list_keys_only = []
-        option.show_core = True
+        option.show_core = not bool(option.env)
         return show_config(state)
     if option.list_envs or option.list_envs_all:
         state.envs.on_empty_fallback_py = False

src/tox/session/env_select.py

@@ -33,6 +33,9 @@ def __iter__(self) -> Iterator[str]:
         if not self.is_all and self._names is not None:  # pragma: no branch
             yield from self._names
 
+    def __bool__(self) -> bool:
+        return bool(self._names)
+
     def __str__(self) -> str:
         return "ALL" if self.is_all else ("<env_list>" if self.is_default_list else ",".join(self))
 

tests/session/cmd/test_legacy.py

@@ -18,6 +18,16 @@ def test_legacy_show_config(tox_project: ToxProjectCreator, mocker: MockerFixtur
     assert outcome.state.conf.options.show_core is True
 
 
+def test_legacy_show_config_with_env(tox_project: ToxProjectCreator, mocker: MockerFixture) -> None:
+    show_config = mocker.patch("tox.session.cmd.legacy.show_config")
+
+    outcome = tox_project({"tox.ini": ""}).run("le", "--showconfig", "-e", "py")
+
+    assert show_config.call_count == 1
+    assert outcome.state.conf.options.list_keys_only == []
+    assert outcome.state.conf.options.show_core is False
+
+
 @pytest.mark.parametrize("verbose", range(3))
 def test_legacy_list_default(tox_project: ToxProjectCreator, mocker: MockerFixture, verbose: int) -> None:
     list_env = mocker.patch("tox.session.cmd.legacy.list_env")