wp-includes/block-template.php:297Strips .php or .html suffix from template file names.
$template_filestringstringfunction _strip_template_file_suffix( $template_file ) { return preg_replace( '/\.(php|html)$/', '', $template_file );}Introduced in 5.8.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/block-template.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.