Fix regression caused in 5.8.1.

changelog/1192.md

@@ -0,0 +1 @@
+- fixed a regression from #1189 where a child template's block override no longer applied to a template {include}d by the parent [#1192](https://github.com/smarty-php/smarty/issues/1192)

src/Runtime/InheritanceRuntime.php

@@ -69,12 +69,8 @@ class InheritanceRuntime {
 	 * @param array $blockNames outer level block name
 	 */
 	public function init(Template $tpl, $initChild, $blockNames = []) {
-		// if called while executing parent template it must be a sub-template with new inheritance root.
-		// A new root is started either by a child template ($initChild) or by a sub-template included
-		// outside of any block rendering (empty source stack); the latter must not inherit the leftover
-		// block overrides of a previously completed inheritance tree (see issue #1189).
-		if (($initChild || empty($this->sourceStack)) && $this->state === 3
-			&& (strpos($tpl->template_resource, 'extendsall') === false)) {
+		// if called while executing parent template it must be a sub-template with new inheritance root
+		if ($initChild && $this->state === 3 && (strpos($tpl->template_resource, 'extendsall') === false)) {
 			$tpl->setInheritance(clone $tpl->getSmarty()->getRuntime('Inheritance'));
 			$tpl->getInheritance()->init($tpl, $initChild, $blockNames);
 			return;

src/Template.php

@@ -260,7 +260,11 @@ public function renderSubTemplate(
 
 		$tpl = $this->smarty->doCreateTemplate($template_name, $cache_id, $compile_id, $this, $caching, $cache_lifetime);
 
-		$tpl->inheritance = $this->getInheritance(); // re-use the same Inheritance object inside the inheritance tree
+		// Re-use the same Inheritance object only inside an active inheritance tree, i.e. when this
+		// (including) template already has one. A template outside any inheritance tree has no
+		// Inheritance object (null); sub-templates it {include}s must then start with their own, so an
+		// {include}d template that uses {block}/{extends} creates a fresh root via getInheritance().
+		$tpl->inheritance = $this->inheritance;
 
 		if ($scope) {
 			$tpl->defaultScope = $scope;