Resolve comment by extracting method

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed PHP8.1 deprecation notices for strftime [#672](https://github.com/smarty-php/smarty/issues/672)
 - Fixed PHP8.1 deprecation errors passing null to parameter in trim [#807](https://github.com/smarty-php/smarty/pull/807)
 - Adapt Smarty upper/lower functions to be codesafe (e.g. for Turkish locale) [#586](https://github.com/smarty-php/smarty/pull/586)
+- Bug fix for underscore and limited length in template name in custom resources [#581](https://github.com/smarty-php/smarty/pull/581)
 
 ## [4.2.1] - 2022-09-14
 

libs/sysplugins/smarty_resource_custom.php

@@ -47,7 +47,7 @@ abstract class Smarty_Resource_Custom extends Smarty_Resource
      */
     public function populate(Smarty_Template_Source $source, Smarty_Internal_Template $_template = null)
     {
-        $source->filepath = $source->type . ':' . substr(preg_replace('/[^A-Za-z0-9.]/', '', $source->name), 0, 25);
+        $source->filepath = $source->type . ':' . $this->generateSafeName($source->name);
         $source->uid = sha1($source->type . ':' . $source->name);
         $mtime = $this->fetchTimestamp($source->name);
         if ($mtime !== null) {
@@ -88,6 +88,17 @@ abstract class Smarty_Resource_Custom extends Smarty_Resource
      */
     public function getBasename(Smarty_Template_Source $source)
     {
-        return basename(substr(preg_replace('/[^A-Za-z0-9.]/', '', $source->name), 0, 25));
+        return basename($this->generateSafeName($source->name));
+    }
+
+    /**
+     * Removes special characters from $name and limits its length to 127 characters.
+     *
+     * @param $name
+     *
+     * @return string
+     */
+    private function generateSafeName($name): string {
+        return substr(preg_replace('/[^A-Za-z0-9._]/', '', (string) $name), 0, 127);
     }
 }