WP 3.5 Compatible version (download here)

No, [caption] was definitely there in old versions (running a old version here to test). So I don’t understand — did the caption shortcode use to allow shortcodes within but it doesn’t any longer?

Caption handling changed in 3.4 https://www.ads-software.com/support/topic/caption-broken-in-new-34-posts?replies=30#post-2933359

But Media Credit doesn’t use either img_caption_shortcode or add_shortcode(‘caption’)…

Yes, but the format of the caption shortcode changed. Before 3.4 it was [caption caption='foo']<img ...>[/caption] while now it is [caption]foo[/caption]. The shortcode still supports the old syntax if you change it manually. I would bet (haven’t tried it, though) that if you do that, [media-credit] parses correctly.

I can confirm that on our site, in several hundred pre-3.4 instances of [caption caption='foo']<img ...>[/caption] the [media-credit] shortcode is parsed correctly, if that helps.

I just checked in a new version that fixes the shortcode parsing. The problem was hidden in the mechanism used to make the >= 3.4 caption backwards compatible: The caption is captured via a regexp and added as an attribute. Of course, the stock WP shortcode does not know about [media-credit] and therefore only looks for <a> and <img>.

If you want to try the fix without a repository checkout, add the following code to media-credit.php:

add_shortcode('wp_caption', 'media_credit_caption_shortcode');
add_shortcode('caption', 'media_credit_caption_shortcode');

function media_credit_caption_shortcode($attr, $content = null) {
        // New-style shortcode with the caption inside the shortcode with the link and image tags.
        if ( ! isset( $attr['caption'] ) ) {
                if ( preg_match( '#((?:\[media-credit[^\]]+\]\s*)(?:<a [^>]+>\s*)?<img [^>]+>(?:\s*</a>)?(?:\s*\[/media-credit\])?)(.*)#is', $content, $matches ) ) {
                        $content = $matches[1];
                        $attr['caption'] = trim( $matches[2] );
                }
        }

        return img_caption_shortcode($attr, $content);
}

Awesome, thanks for addressing!
Didn’t Nacin say not to use add_shortcode(‘wp_caption’), though?

He did, but I think that only applies for plugins that want to change the shortcode output. Here, I don’t see any other way to do it. At the point of the filter, the $content is already mangled beyond repair.

I’m not familiar with how Media Credit stores its information. When img_caption_shortcode() parses out the image and caption from $content, what happens to the media credit? How is it “mangled”?

Slightly simplified (no attributes) code for media-credit with captions:
[caption][media-credit]<a><img></a>[/media-credit] My Caption[/caption]

The regexp in media.php starts matching at the <a> tag and ignores everything before it. This eliminates the [media-credit] tag and its attributes and leaves a dangling [/media-credit] that can’t be parsed by the shortcode function.

Nacin, any ideas?

Has anyone tried the current trunk version (with the caption shortcode fix)?

No-one? If there are no objections, I’d like to release the current version to get some feedback. Since the current version is broken on 3.5/3.6 in multiple ways, I see no harm that could befall users.

Sorry Pepe,

I fully intend on revisiting this project, but I have a ton of projects on my plate right now. I’ll see if I can’t do some beta testing for my particular situation this weekend.

Hi Pepe,

Slight bug I’ve found. When inserting the media in visual editor, the initial [media-credit] tag is not inserted. (however, the [/media-credit] is). In the text editor, this is not a problem. Additionally, if you switch from text editor, to visual, and back the first [media-credit] seems to disappear.