Implement a check for edge cases where the function name terminates w…

…ith an underscore.

test/php/gutenberg-coding-standards/Gutenberg/Sniffs/NamingConventions/ValidBlockLibraryFunctionNameSniff.php

@@ -104,7 +104,9 @@ private function processFunctionToken( File $phpcsFile, $stackPointer ) {
 			$prefix                      = rtrim( $prefix, '_' );
 			$allowed_function_prefix     = $prefix . '_' . $this->sanitize_directory_name( $parent_directory_name );
 			$allowed_function_prefixes[] = $allowed_function_prefix;
-			$is_function_name_valid      |= 0 === strpos( $function_name, $allowed_function_prefix );
+			// Verify the validity of the name and ensure that a function name does not end with an underscore.
+			$regexp                      = sprintf( '/^%s(|_.+)$/', preg_quote( $allowed_function_prefix, '/' ) );
+			$is_function_name_valid      |= (1 === preg_match( $regexp, $function_name ));
 		}
 
 		if ( $is_function_name_valid ) {