Filter logic has been put into the template loader while it not belongs there.

[hakre]

Some time ago, filter logic has been introduced in the template-loader. Looks like a fix for the inability to handle attachments propperly (WP misses more and more a strict request parsing so that newer features tend to introduce more and more bugs).

The code has not been removed yet. It should be removed there or put into a more appropriate location.

The code in question is:

remove_filter('the_content', 'prepend_attachment');

in /wp-inclueds/template-loader.php around line 30.

[hakre]

related: #6357 , code in question was introduced by ryan

[Ninos Ego]

Is it planned to remove this filter in one of the next releases? I think this hack should be removed from code, otherwise you'll see the attachments image on the attachment page if you're using the the_content filter for compiling shortcodes in widgets or somewhere else.
For theme developers it should be very easy to add a new line of code to their single-attachment.php (or use map the attachment image to the post_thumbnail function). If you want I can publish a patch...

Trac ticket: https://core.trac.wordpress.org/ticket/10275

[desrosj]

It's not exactly clear what problem this addresses. But I can't find a scenario where prepend_attachment() is actually utilized in Core as a filter anymore.

In the latest version of Core (currently 6.6), it's added as a default filter for the_content, and only removed when is_attachment is the template file. But when the filter is called when displaying non-attachment posts, the function returns early.

A ​brief check of the plugin directory shows that plugins are either calling prepend_attachment() directly or adding it as a filter for their own custom hooks. So I don't expect anything to break related to 3rd-party usage.

I've opened a PR and removed the related code and default filter, and no tests broke. I'm moving this to the 6.7 milestone for a second set of eyes before committing.

[sppramodh]

Test Report

This report validates that the changes in the patch do not introduce any issues and work as intended.

Patch tested: ​https://github.com/WordPress/wordpress-develop/pull/7321

Environments Tested

Environment 1

• WordPress Playground
• WordPress 6.7 (Patch applied)
• PHP: 7.4.29
• Browser: Google chrome 129.0.6668
• Theme: Twenty Twenty-Four (Version 1.2)
• Active Plugins:
  • Toggle wp_attachment_pages_enabled

Environment 2

• WordPress Playground
• PHP: 8.0
• WordPress: 6.6.2
• Browser: Google chrome 129.0.6668
• Theme: Twenty Twenty-Four (Version 1.2)
• Active Plugins:
  • Toggle wp_attachment_pages_enabled

Steps followed

1 Enable Attachment Pages:
Since attachment pages are fully disabled in WordPress 6.4 and later, the "Toggle wp_attachment_pages_enabled" plugin was used to enable attachment pages for testing.

2 Media Upload:
Uploaded an image to the Media Library.

3 View Attachment Page:

• On WordPress 6.6.2 (without the patch), the image was visible on the attachment page.
• On WordPress 6.7 (with the patch applied), the image did not appear on the attachment page.

screenshot from WordPress 6.7 patch applied

screenshot from WordPress 6.6.2

4 Behavior When Attachment Pages are Disabled (Default):
There was no change in how the images were displayed when viewing media items.

5 Custom Shortcode Testing:

• Created a custom shortcode that utilizes the the_content filter for compiling shortcodes.
• Developed a separate shortcode to display an attachment by ID.

6 Testing Shortcodes on the Header:
Added the custom shortcode and the attachment shortcode to the header, linking to a PDF (Download rates).

screenshot from WordPress 6.7 patch applied

screenshot from WordPress 6.6.2

7 Observations:

• On WordPress 6.6.2, the attachment was automatically added to the header, appearing multiple times due to the the_content filter's effect when using shortcodes.
• On WordPress 6.7 (with the patch), no such issue occurred on the attachment page. The attachment did not appear multiple times.

8 Compatibility Testing with WooCommerce:
Installed WooCommerce to verify if the shortcodes in the header caused any issues on WooCommerce pages.
No problems were found with WooCommerce active.

Actual Results

• ✅ Issue resolved with patch.

[desrosj]

6.7 RC1 is due out any moment. Unfortunately, this one missed the deadline so I'm going to punt this.

[desrosj]

@sppramodh Thanks for the testing you did! Based on the results, the PR is not the right approach as images will disappear from attachment pages in some scenarios. Can you share the shortcodes you were using to test?

I'm leaning towards closing this as a wontfix. This is such a long-standing "temporary" fix and the risks associated with changing this are probably not worth the trade off.

This results in images disappearing from single attachment pages in some themes, so not the right approach.

[sppramodh]

Sure, Please find the shortcode, i used for testing

function display_attachment_by_id( $atts ) {
    $atts = shortcode_atts( array(
        'id' => 0,
    ), $atts, 'attachment_id' );

    $attachment_id = intval( $atts['id'] );

    // Check if a valid attachment ID is provided
    if ( $attachment_id <= 0 ) {
        return 'Invalid attachment ID.';
    }

    // Get the attachment HTML markup (image, file link, etc.)
    $attachment_html = wp_get_attachment_link( $attachment_id );

    // If attachment is found, return the HTML, otherwise return a message
    return $attachment_html ? $attachment_html : 'Attachment not found.';
}

add_shortcode( 'attachment_id', 'display_attachment_by_id' );

Usage:

[attachment_id id="12"]

Let me know if further details or additional tests are needed!

[audrasjb]

As per today's bug scrub.
Given the above discussion, decision was made to close this ticket as wontfix for now. Please feel free to reopen it if a new approach is discussed.