Sanitize theme slugs for usage in PHP function names (#381)

Co-authored-by: swissspidy <841956+swissspidy@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: Copilot

features/scaffold.feature

@@ -116,6 +116,23 @@ Feature: WordPress code scaffolding
       """
     And the return code should be 1
 
+  @theme
+  Scenario: Scaffold a child theme with dots in the slug
+    Given a WP install
+    And I run `wp theme path`
+    And save STDOUT as {THEME_DIR}
+
+    When I run `wp scaffold child-theme my-theme-2.0.1 --parent_theme=umbrella`
+    Then the {THEME_DIR}/my-theme-2.0.1/functions.php file should exist
+    And the {THEME_DIR}/my-theme-2.0.1/functions.php file should contain:
+      """
+      function my_theme_2_0_1_parent_theme_enqueue_styles()
+      """
+    And the {THEME_DIR}/my-theme-2.0.1/functions.php file should contain:
+      """
+      add_action( 'wp_enqueue_scripts', 'my_theme_2_0_1_parent_theme_enqueue_styles' );
+      """
+
   @tax @cpt
   Scenario: Scaffold a Custom Taxonomy and Custom Post Type and write it to active theme
     Given a WP install

src/Scaffold_Command.php

@@ -513,7 +513,7 @@ public function child_theme( $args, $assoc_args ) {
 
 		$data                = wp_parse_args( $assoc_args, $defaults );
 		$data['slug']        = $theme_slug;
-		$data['prefix_safe'] = str_replace( [ ' ', '-' ], '_', $theme_slug );
+		$data['prefix_safe'] = preg_replace( '/[^a-zA-Z0-9_]/', '_', $theme_slug );
 		$data['description'] = ucfirst( $data['parent_theme'] ) . ' child theme.';
 
 		$theme_dir = WP_CONTENT_DIR . "/themes/{$theme_slug}";