Fix for unable to lock any extension

[itsmevichu]

Fix for #16203

This issue arises because the page_config lacks context regarding the locked plugins.

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[krassowski]

Looks good, but I think we need to add a test here. In particular something directly hitting the get() endpoint of PluginHandler API:

jupyterlab/jupyterlab/handlers/plugin_manager_handler.py

Line 21 in f3867b0

async def get(self):

It would look similar to:

jupyterlab/jupyterlab/tests/test_custom_css_handler.py

Lines 21 to 37 in f3867b0

	@pytest.fixture
	def jp_server_config(jp_server_config, tmp_path):
	config = jp_server_config.copy()
	config["LabApp"]["custom_css"] = True
	return config
	async def test_CustomCssHandler(tmp_path, jp_serverapp, labserverapp, jp_fetch):
	custom_path = tmp_path / "config" / "custom"
	# Check we are placing the custom.css file in the appropriate folder
	assert str(custom_path) in jp_serverapp.web_app.settings["static_custom_path"]
	custom_path.mkdir(parents=True, exist_ok=True)
	(custom_path / "custom.css").write_text(CUSTOM_CSS)
	response = await jp_fetch("custom", "custom.css", method="GET")
	assert response.code == 200
	assert response.body.decode().replace(os.linesep, "\n") == CUSTOM_CSS

but using lock_extension and unlock_extension to setup the state, similarly to how disable/enable are used in:

jupyterlab/jupyterlab/tests/test_jupyterlab.py

Lines 553 to 571 in f3867b0

	def test_disable_extension(self):
	options = AppOptions(app_dir=self.tempdir())
	assert install_extension(self.mock_extension, app_options=options) is True
	assert disable_extension(self.pkg_names["extension"], app_options=options) is True
	info = get_app_info(app_options=options)
	name = self.pkg_names["extension"]
	assert info["disabled"].get(name) is True
	assert not check_extension(name, app_options=options)
	assert check_extension(name, installed=True, app_options=options)
	assert disable_extension("@jupyterlab/notebook-extension", app_options=options) is True
	info = get_app_info(app_options=options)
	assert info["disabled"].get("@jupyterlab/notebook-extension") is True
	assert not check_extension("@jupyterlab/notebook-extension", app_options=options)
	assert check_extension(
	"@jupyterlab/notebook-extension", installed=True, app_options=options
	)
	assert info["disabled"].get(name) is True
	assert not check_extension(name, app_options=options)
	assert check_extension(name, installed=True, app_options=options)