Get markup for post without loading into the template

Question

I am writing a shortcode plugin that displays posts according to some parameters passed into the shortcode. I have the wp_query to get the posts and now I am trying to get the markup for the posts according to the theme's template files.

In essence, get_template_part is exactly what I want... except that it directly loads the markup into the template. I want to get the markup for the content, perform a little post-processing and then return the markup for the shortcode. Essentially,

$listings = new WP_Query(...);
while ( have_posts() ) {
    $markup .= get_template_part('content', $post->post_type);
}
return $markup

Except this obviously isn't the way that get_template_part works. How do I get the markup for a post without rendering the markup into the page?

Answer 1

I couldn't figure out a WordPress way to do this and looking at the WP source, it looks like this probably will never really be possible. However, I was able to get a solution using vanilla PHP by redirecting standard output into a buffer and loading the buffer into a variable.

$listings = new WP_Query(...);
ob_start();
while ( have_posts() ) {
    get_template_part('content', $post->post_type);
}
$markup = ob_get_contents();
ob_end_clean();
return $markup

Answer 2

If you're looking for just the content from a post before it gets loaded into a template, then you're probably looking for get_the_content().