Developer advisory: Deprecation of wc_current_theme_is_fse_theme()

As of WooCommerce 9.9, the function wc_current_theme_is_fse_theme() will be deprecated. This function previously identified whether the current theme supports Full Site Editing (FSE), but it is now being replaced with the core WordPress function wp_is_block_theme(), which offers a more standardized and reliable approach.

The details

The wc_current_theme_is_fse_theme() function was originally introduced to detect if the current theme supports FSE by checking for block-template support. However, WordPress core now includes the wp_is_block_theme() function, which serves the same purpose in a more consistent and better-supported way.

As a result, wc_current_theme_is_fse_theme() has been marked as deprecated in WooCommerce 9.9 in PR #56747 and will be removed in a future release. Developers are encouraged to migrate to the native WordPress function wp_is_block_theme() to reduce redundancy and future-proof their code.

Important note: Beginning with WordPress 6.8, wp_is_block_theme() will issue a debug notice if it is called before the theme directory has been registered. This means it must not be used too early in the execution flow. after_theme_setup and init are safe places to invoke the wp_is_block_theme().

How can I tell if this affects me?

You are affected by this advisory if your code (whether in a theme, plugin, or custom code) calls the wc_current_theme_is_fse_theme() function.

To check:

• Search your codebase for any instances of wc_current_theme_is_fse_theme().
• If WP_DEBUG is enabled, using this function will trigger a _deprecated_function() notice in your debug log, helping to identify exactly where it’s being called.

What action should I take?

If your code uses wc_current_theme_is_fse_theme(), you should replace it with wp_is_block_theme().

Both functions return a boolean indicating whether the current theme is a block (FSE) theme, so the update should be simple. Here’s a quick before-and-after example:

Before:

if ( wc_current_theme_is_fse_theme() ) {
    // Logic for FSE themes
}

After:

if ( wp_is_block_theme() ) {
    // Logic for FSE themes
}

Make sure to test your updated code to confirm that it behaves as expected with both block and classic themes.

Although the deprecated function will continue to work in WooCommerce 9.9, but we strongly recommend migrating to wp_is_block_theme() as soon as possible to avoid issues in future releases.