The export_wp() function inserts empty <wp:comment> data when get_comment() returns a false or empty value

[WPExplorer]

If you wish to exclude comments from the WordPress export you can use the following code:

add_action( 'export_wp', function() {
    add_filter( 'get_comment', '__return_false' );
} );

However, the function will still loop through empty values for the $comments array inserting unnecessary <wp:comment> items.

If you wish to exclude comments from the WordPress export you can use the following code:

add_action( 'export_wp', function() {
    add_filter( 'get_comment', '__return_false' );
} );

However, the function will still loop through empty values for the $comments array inserting unnecessary <wp:comment> items.

[freewebmentor]

Hi @wpexplorer! 👋

Thank you for your contribution to WordPress! 💖

[hellofromTonya]

While scrubbing for 6.6.x minor, dove into which WordPress Version introduced this bug and code. It was in WP 4.4 via [33891].

As it has a clear explanation and patch, moving it into 6.7 cycle for possible resolution.

[lbones]

I am working on testing this one! I am planning on recreating the issue in WP 6.6., and then running the patch to verify if the issue has been resolved. I am using the WordPress Playground, but can test through the CLI or whatever you may need.

In the PlayGround, I did notice that the user is not able to enter an empty comment. To recreate, I wrote a comment, and then went into the WordPress editor and removed the text in the comment.

[lbones]

This is the test that was done using the patch [from PR=6574] which was PHP 8.2 and WP 6.6.2

[lbones]

Another view of the issue in the patch [with PR=6574] using PHP 8.2 and WP 6.6.2

[lbones]

Initially, I thought that the issue was that the comments were coming through whether or not they contained content. I realized upon further investigation that the issue, is if the person wants to run

add_action( 'export_wp', function() {
    add_filter( 'get_comment', '__return_false' );
} );

then the patch, which contains an array_filter does work. Recommendation would be to add an export option without comments instead of the current patch.

Reasoning: This very niche solution makes the entire get_comment call in the wp_export function slower. The array_filter in combination with array_map creates two maps (could probably have a map_reduce like function), and with the for loop, we are going through all of the comments thrice.

P.S. I plan on opening a new ticket with the commenting editing issue I found. I believe the checks on modify_item in the comment controller just needs to be a little more robust.

[stoyangeorgiev]

This one was discussed at a bug-scrub. By the looks of it this one needs a bit more time, and with RC1 right around the corner, moving this one to 6.8. Cheers!

[mdibrahimk48]

Test Report:

The applied patch [PR=6574] shows no changes in functionality when tested with PHP 8.3 and WordPress 6.7.1.

Observation:

---

Attempting to submit an empty column does not work. However, when using the WordPress editor, removing text in a comment is possible without issues.

[desrosj]

This looks good, but I'd love to see some unit tests that demonstrate the failure and confirming that the change fixes the issue.

Trac ticket: https://core.trac.wordpress.org/ticket/61244

This PR adds unit tests for the patch present to verify the behavior of comment filtering during exports.

The new test ensures that when comments are filtered out using get_comment filter, no empty <wp:comment> tags appear in the export XML.

Run the tests:

npm run test:php -- --filter=Tests_Admin_ExportWp

[saurabh.dhariwal]

WordPress Version 6.7
Issue Summary

Problem: Previously, the system allowed users to submit blank comments on posts and pages.
Expected Behavior: The system should prevent users from submitting empty comments.

Testing Steps & Results

Navigate to a post/page and open the comment section. ✅
Attempt to submit a blank comment. ✅
Observe the system’s response. ✅

Result: The issue could not be reproduced. The system correctly prevents blank comments from being submitted.

Test Conclusion

Status: ✅ Not Reproduced
Remarks: The issue appears to be resolved or was not present in the tested environment. Further verification may be needed if reported again.

[audrasjb]

Moving to 6.9 as we're too close from beta 3 and this still needs testing.

[SirLouen]

Bug Reproduction Report

Description

❌ This report can't validate that issue can be reproduced.

Patch tested: ​https://github.com/WordPress/wordpress-develop/pull/8383.diff

Environment

• WordPress: 6.9-alpha-60093-src
• PHP: 8.2.28
• Server: nginx/1.27.5
• Database: mysqli (Server: 8.4.5 / Client: mysqlnd 8.2.28)
• Browser: Chrome 135.0.0.0
• OS: Windows 10/11
• Theme: Twenty Twenty-Five 1.2
• MU Plugins: None activated
• Plugins:
  • Test Reports 1.2.0

Bug Reprodution Steps

1. Added the provided code:

<?php
add_action( 'export_wp', function() {
    add_filter( 'get_comment', '__return_false' );
} );

2. Go to Tools > Export > Download Export File (for Posts, Categories: All, Authors: All, Status: All, No dates selected)

3. ❌ I attach the resulting XML, full of Warnings.

Actual Results

1. ❌ Can't reproduce this problem

Additional Notes

1. Note that I'm using Xdebug for debugging (this is why warnings in the resulting file, show xdebug errors).
2. This XML file can be opened as an HTML to better see all the errors
3. @WPExplorer are you confident that this provided snippet works?
4. @abcd95 have you been able to reproduce it?

Supplemental Artifacts

• Resulting XML

[SirLouen]

Also noting as commented, that apart that I'm completely unable to reproduce this "filter" as is, this will bring some additional performance issues.

Personally I would consider here a close as wontfix

[jorbin]

While the patch might not be exactly what it is needed, this is a problem that should be solved.

[SirLouen]

Replying to jorbin:

While the patch might not be exactly what it is needed, this is a problem that should be solved.

Have you been able to reproduce it? Can you provide the steps on how you did?

What needs refresh?

[jorbin]

To reproduce I made an mu-plugin with the code from the ticket description

<?php
add_action( 'export_wp', function() {
    add_filter( 'get_comment', '__return_false' );
} );

I then used wp-cli to run export_wp() and observed that it contains an empty comment.

The ​refresh is described on the PR.

[SirLouen]

Replying to jorbin:

To reproduce I made an mu-plugin with the code from the ticket description

Ok, I can remember now what I was thinking back in the day:

All the warnings are being caused by an unexpected value (the false)

When I first reviewed get_comment I could not understand why the person was returning a false because get_comment is not expecting to return a bool value:

@return WP_Comment|array|null Depends on $output value.

But a null at best.

There is no sanitization of what the user can return after the filter and what gets to the next conditional block (which can end returning whatever value has been passed through the filter).

So here I was thinking: "If false was being used is normal that everything completely fails".

But after your comment, I'm rethinking this: if he had used __return_null instead, he could also expect to wipe all comments from export. And since null and false might behave similarly with array_filter then we could expect the same result whatever the formula we use (despite it's a little out of the boundaries)

So I wonder if:
A) get_comment should also be reviewed to accept a bool return, or
B) better sanitize the "filtered comment".

The ​refresh is described on the PR.

Oh, you meant changes-requested for the tests 👍. I'm going to fix this.
cc @abcd95

can we utilize the get_the_export() method

Yes, I completely missed that. Thanks for pointing out.

[wildworks]

This ticket was brought up in today's bug scrub. I think the PR is in good shape, and I would like to suggest at least removing changes-requested and adding needs-testing.

If there is no Activity, I will punt it to 7.0 milestone.

[mabfahad]

I tested this with the latest WordPress version (6.8.3) on a fresh installation.
I created several posts with comments and also deleted some comments directly from the database to simulate missing data.

In all my tests, get_comment() did not return false, and no empty <wp:comment> elements were found in the exported WXR file.

It appears that this issue no longer occurs in the current version of WordPress.

[wildworks]

Since the RC1 release is approaching, I'd like to punt this ticket to 7.0.

It appears that this issue no longer occurs in the current version of WordPress.

@mabfahad, I think this is the correct procedure to reproduce the problem.

https://core.trac.wordpress.org/ticket/61244#comment:22

I think the failing test is unrelated to the changes in the PR.

[westonruter]

As part of this, the get_comment filter should also be updated to indicate that it can return null as well:

src/wp-includes/comment.php

@@ -240 +240 @@
          *
          * @since 2.3.0
          *
-         * @param WP_Comment $_comment Comment data.
+         * @param WP_Comment|null $_comment Comment data.
          */
         $_comment = apply_filters( 'get_comment', $_comment );
+        if ( ! ( $_comment instanceof WP_Comment ) ) {
+                return null;
+        }
 
         if ( OBJECT === $output ) {
                 return $_comment;

Otherwise, if someone tries to return null (or false) in a callback to the get_comment filter, then technically they are violating the filter's allowed types.

See also: https://core.trac.wordpress.org/ticket/61244#comment:31

[westonruter]

In 61369:

Export: Update export_wp() to handle get_comment() returning null due to filter.

The get_comment filter now explicitly documents returning null in addition to a WP_Comment object. This allows the filter to be used to exclude comments from an export. The get_comment() function already supported returning null.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/8383

Props abcd95, WPExplorer, desrosj, mukesh27, westonruter, SirLouen, lbones, mdibrahimk48, audrasjb, jorbin, wildworks, hellofromTonya, saurabh.dhariwal, mabfahad.
Fixes #61244.