Blocks unavailable when new WP_Query is used inside render callback

[jomurgel]

Describe the bug
Use of a new WP_Query throws no errors, but breaks admin render of blocks using them.

To Reproduce
Steps to reproduce the behavior:

1. Utilize new WP_Query over a get_posts or get_recent_posts function
2. Update block and save.
3. Refresh page (or exit and return)
4. Will see a random post or will return a post in class editor.

post_content does, in fact, save the block data as expected and front-end render is fine. This effects only admin-facing blocks.

Potentially Related
#5572
#7427
#4733

Expected behavior
Reload/return to post, should see Gutenberg block.

Screenshots
Block added:

Refresh (when new WP_Query is used instead of wp_get_recent_posts ):

Desktop (please complete the following information):

• OS: MacOS 10.13.6
• Browser ALL

Additional context

• Occurs with v 3.2

[chrisvanpatten]

I downloaded your block and messed around a bit. To be more specific, it's not exactly related to WP_Query, it's the use of $query->the_post().

If you run the WP_Query and just use the $query->posts array directly (iterate over it, directly access $post->title, $post->ID, etc.) it will work okay, because it won't override the global $post.

Your change to use get_post() avoids a the_post() call which is why it works while the WP_Query version didn't.

Also related to #7582 and core #18408.

You can also cheat a bit and save the global $post before resetting it, then set it again after your query. There's a good example here courtesy of @aduth.

[obenland]

I downloaded your block

Where can this block be found?