Video and audio shortcode callback functions wrapped in a filter, but executed too early to be hooked onto

[ericlewis]

In the add_shortcode calls for the video and audio shortcodes, both seem to offer developers the option to register their own callback for this shortcode by wrapping the default callback in a wrapper. However, media.php is loaded before even mu-plugins, so there is no way save hacking core to add a filter here.

[SergeyBiryukov]

Confirmed, the filters are currently unusable:
wp_audio_shortcode_handler: tags/3.6.1/wp-includes/media.php#L949​
wp_video_shortcode_handler: tags/3.6.1/wp-includes/media.php#L1093​

[SergeyBiryukov]

25313.patch​ is an attempt to add all the default shortcodes on init with the highest priority, like we do for create_initial_post_types().

[nacin]

I'm OK with 25313.patch​, though:

• It needs a better name. add_shortcodes() sounds like a multiple-shortcode version of add_shortcode(), not a core registration. wp_add_initial_shortcodes() perhaps.
• As always, I am curious what this might break...

[nacin]

To be honest, though, I'd rather just remove these filters and force everything to go through wp_audio_shortcode() and wp_video_shortcode(). Then, have an early filter in both of those functions that allow short-circuiting.

This pattern for existing shortcodes came up *huge* when we changed how the caption shortcode worked, when we put the caption inside the shortcode content. Huge forwards compatibility win.

[SergeyBiryukov]

25313.2.patch​ uses wp_add_initial_shortcodes().

[SergeyBiryukov]

25313.3.patch​ implements comment:5.

[ericlewis]

Piggybacking on Sergey's work, attachment:25313.4.patch​:

• changes the new filter's name to wp_(audio|video)_shortcode_override, as the filter isn't a handler
• passes $instances into the filter, as this can be handy in the overriding function to give separate media instances independent names.

[SergeyBiryukov]

25313.5.patch​ changes the default value to an empty string, for consistency with the post_gallery filter.

[ericlewis]

#25312 was marked as a duplicate.

[nacin]

We should properly document these. Also, while post_gallery is a good model to follow, I'm not sure I love '' !==. We use false more often, though ideally we actually use null wherever possible. Or so goes my idealistic thinking, anyway.

Is there a compelling reason to use ''? I'd think any string returned should be obeyed. Returning nothing is valid in some contexts, I'd suggest.

[ericlewis]

attachment:25313.6.patch​ adds hook documentation, and changes the pre-filtered value to null.

[SergeyBiryukov]

In 25484:

Replace non-functional 'wp_audio_shortcode_handler' and 'wp_video_shortcode_handler' filters with 'wp_audio_shortcode_override' and 'wp_video_shortcode_override'.

props ericlewis, SergeyBiryukov.
fixes #25313.

[SergeyBiryukov]

25313.7.patch​ makes the arguments more consistent with the ones of img_caption_shortcode and post_gallery filters, per the ​IRC discussion.

[SergeyBiryukov]

In 25485:

Make the arguments of 'wp_audio_shortcode_override' and 'wp_video_shortcode_override' more consistent with the ones of 'img_caption_shortcode' and 'post_gallery' filters.

see #25313.