When layout is disabled root view model is set as layout

[Xerkus]

Bug Report

Normally layout is always present either via a constructor argument or via view model parameter override.

However, layout can be disabled and then bug happens where current view model becomes the layout and can be messed up from the child view scripts via layout view helper.

You may also pass a boolean false value to either addDefaultParam() or via the template variables for the layout key; doing so will disable the layout.

Here root view model is always selected as root:

mezzio-laminasviewrenderer/src/LaminasViewRenderer.php

Lines 188 to 195 in e103b3e

	private function renderModel(
	ModelInterface $model,
	RendererInterface $renderer,
	?ModelInterface $root = null
	): string {
	if (! $root) {
	$root = $model;
	}

And here layout is not injected as a new root view model when layout is disabled.

mezzio-laminasviewrenderer/src/LaminasViewRenderer.php

Lines 123 to 129 in e103b3e

	$useLayout = false !== $viewModel->getVariable('layout', null);
	if ($useLayout) {
	$viewModel = $this->prepareLayout($viewModel);
	}
	return $this->renderModel($viewModel, $this->renderer);
	}

When template name or a single level view model is passed layout helper is too late to mess up since it is already getting rendered when $this->layout() can be invoked.
Bug will manifest only with nested view models and when layout altering happens from inside children view scripts.

[gsteel]

Is this issue present on PR #74 ?

[Xerkus]

It is present there as well.