get_the_excerpt is taking PHP out of memory in a block rendering

[maximebj]

Issue Overview

I'm rendering a block in PHP that display another post preview card so I simply use (in the render_callabck) :

$id = $attributes['postID'];

$post = get_post( $id );
$excerpt = get_the_excerpt( $id );

I get a Fatal error: Allowed memory size of... from PHP from get_the_excerpt()
It look like it's too much for WP to parse the gutenberg saved markup

The targeted post only has a few paragraphs and a read more tag.

The issue does not happen if I set manually an excerpt in the inspector.

This memory issue does not occur outside a block rendered in PHP

Steps to Reproduce

1. create a post with gutenberg
2. add a read more block but no excerpt on inspector
3. create a block rendering in PHP
4. on the render hook, try to get_post and get_the_excerpt

Expected Behavior

display everything

Current Behavior

Allowed memory size of

Todos

• Tests
• Is it a legit issue?
• find where occurs the memory leak and why

[Kluny]

Hey Maxime, could you clarify what you're doing on this step?

create a block rendering in PHP

I'd like to try to test this.

[maximebj]

Yes ! I'm creating some blocks (and making a plugin of it) and one of my block is about featuring another post like this :

So my block in html is just

<!-- wp:gutenblocks/post {"postID":158} /-->

And the whole thing is rendered via PHP.

When I'm in the render_callback, if I try to call get_excerpt() I got this error

[Theremingenieur]

And when might we expect a solution? Seems like I'm not the only one who sees this as an urgent and blocking problem...

[jomurgel]

@Theremingenieur are you working inside a new WP_Query loop or a going through wp_get_recent_posts results in a foreach loop?

I'm seeing the same behavior, but am also seeing some interesting differences depending on how I attempt to display results. Attempting to debug.

[Theremingenieur]

@jomurgel : I have no idea. I’m just eager to finally use the post block which is part of the plugin developed by @maximebj who opened this issue. He says he can’t fix his plugin until the underlying issue is solved...

[maximebj]

The issue is not there if I make a standard WP_Query and use the_excerpt

The issue only occurs when I use get_post and get_the_excerpt( $id) with an infinite loop.

I don't understand why there is a difference, but if it can help.

Thank you!

[TimothyBJacobs]

I think this happens when the excerpt is empty for a post because:

get_the_excerpt with a post ID ends up calling wp_trim_excerpt. If no excerpt, it tries to build one manually from the post content. This post content is accessed via get_the_content which uses the global $post. This doesn't take into account that get_the_excerpt can seemingly be used outside of the loop. This is kinda documented in the developer docs, https://developer.wordpress.org/reference/functions/get_the_excerpt/#user-contributed-notes.

It seems core ends up avoiding the fatal error because it calls strip_shortcodes on the content before passing it into the_content filter.

Stack trace

``` # | Time | Memory | Function | Location -- | -- | -- | -- | -- 1 | 0.2005 | 398640 | {main}( ) | .../index.php:0 2 | 0.2010 | 398928 | require( '/app/public/wp-blog-header.php' ) | .../index.php:17 3 | 0.2864 | 2905128 | require_once( '/app/public/wp-includes/template-loader.php' ) | .../wp-blog-header.php:19 4 | 0.2890 | 2947912 | include( '/app/public/wp-content/themes/twentysixteen/single.php' ) | .../template-loader.php:74 5 | 0.3255 | 3075008 | get_template_part( ) | .../single.php:19 6 | 0.3255 | 3075584 | locate_template( ) | .../general-template.php:155 7 | 0.3259 | 3075696 | load_template( ) | .../template.php:647 8 | 0.3262 | 3076056 | require( '/app/public/wp-content/themes/twentysixteen/template-parts/content-single.php' ) | .../template.php:690 9 | 0.3268 | 3076056 | the_content( ) | .../content-single.php:22 10 | 0.3268 | 3076192 | apply_filters( ) | .../post-template.php:240 11 | 0.3268 | 3076592 | WP_Hook->apply_filters( ) | .../plugin.php:203 12 | 0.3269 | 3078496 | do_blocks( ) | .../class-wp-hook.php:286 13 | 0.3270 | 3082240 | WP_Block_Type->render( ) | .../blocks.php:181 14 | 0.3270 | 3082240 | {closure:/app/public/wp-content/plugins/demo-talk/php/latest-author-post.php:5-45}( ) | .../class-wp-block-type.php:107 15 | 0.3294 | 3103048 | get_the_excerpt( ) | .../latest-author-post.php:35 16 | 0.3294 | 3103496 | apply_filters( ) | .../post-template.php:397 17 | 0.3294 | 3103896 | WP_Hook->apply_filters( ) | .../plugin.php:203 18 | 0.3294 | 3105400 | wp_trim_excerpt( ) | .../class-wp-hook.php:288 19 | 0.3294 | 3105512 | apply_filters( ) | .../formatting.php:3313 20 | 0.3294 | 3105912 | WP_Hook->apply_filters( ) | .../plugin.php:203 21 | 0.3294 | 3106664 | do_blocks( ) | .../class-wp-hook.php:286 22 | 0.3295 | 3110408 | WP_Block_Type->render( ) | .../blocks.php:181 23 | 0.3296 | 3110408 | {closure:/app/public/wp-content/plugins/demo-talk/php/latest-author-post.php:5-45}( ) | .../class-wp-block-type.php:107 24 | 0.3306 | 3129024 | get_the_excerpt( ) | .../latest-author-post.php:35 25 | 0.3307 | 3129472 | apply_filters( ) | .../post-template.php:397 26 | 0.3307 | 3129872 | WP_Hook->apply_filters( ) | .../plugin.php:203 27 | 0.3307 | 3130624 | wp_trim_excerpt( ) | .../class-wp-hook.php:288 28 | 0.3307 | 3130736 | apply_filters( ) | .../formatting.php:3313 29 | 0.3307 | 3131136 | WP_Hook->apply_filters( ) | .../plugin.php:203 30 | 0.3307 | 3131888 | do_blocks( ) | .../class-wp-hook.php:286 31 | 0.3307 | 3135632 | WP_Block_Type->render( ) | .../blocks.php:181 ```

[maximebj]

Thank you for theses valuable informations

So as you say if I do a real WP Query there is no issue. And if a post has a manual excerpt there is no issue too.

I may close this issue as it is not really Gutenberg related, what do you think?

[TimothyBJacobs]

Yeah, seems more like an issue with Core and the strip_shortcodes solution clearly won't work for Gutenberg.

[Luehrsen]

Yeah, a 'normal' WP_Query doesn't help either. This is our current test setup:

        $args = array(
		'posts_per_page'   => $attributes['postsToShow'],
		'orderby'          => $attributes['orderBy'],
		'order'            => $attributes['order'],
		'post_type'        => 'post',
		'post_status'      => 'publish',
		'ignore_sticky'    => true,
	);

	// The Query
	$query = new WP_Query( $args );

	$block_content = '';

	// The Loop
	if ( $query->have_posts() ) {
		while ( $query->have_posts() ) {
			$query->the_post();
			// do something
			$block_content .= get_the_excerpt();
		}
	}
	// Restore original Post Data
	wp_reset_postdata();

	return $block_content;

It runs into memory issues as expected.

[chrisvanpatten]

See also #7268.

[vguerrerobosch]

I came up with the same issue when creating a dynamic block and using get_the_excerpt in render block callback function. I solved it with

if ( doing_filter( 'get_the_excerpt' ) ) {
    return false;
}

which solves the infinite nesting and accomplishes my desired behavior.

[obenland]

wp_trim_excerpt applies the the_content filter, which do_blocks() is hooked into, causing an infinite loop and the memory error.

We could probably just remove the filter at the beginning of do_blocks() to make sure it only runs once.

[TimothyBJacobs]

I thought that wouldn't work because if you are trying to generate an excerpt from a post with blocks, without doing the blocks, you'll end up with block comments instead of the actual content.

[obenland]

To my understanding, that would only apply to dynamic blocks. Shortcodes are currently stripped too, so there should be any inconsistency there. Regular block should display fine, based on their stored markup.

[TimothyBJacobs]

Wouldn't you still end up with the comments at top? I guess, depending on how the person is using get_the_excerpt, they would be hidden from display because they are HTML comments. But I thought it was important that block comments were stripped completely, not just hidden from view.

[obenland]

Not in my testing so far. wp_strip_all_tags() should take care of that

[TimothyBJacobs]

Ah, awesome!

[obenland]

A better fix could be to just strip dynamic blocks when trying to generate an excerpt