Notice: Undefined index in WordPress 5.9 Beta

[kafleg]

When we go to Appearance > Editor and then to Template Parts, I see this notice.

<b>Notice</b>: Undefined index: path in <b>E:\laragon\www\59-beta\wp-includes\rest-api.php</b> on line <b>2854</b><br />

Screenshot: ​https://prnt.sc/21dpjkw

[costdev]

Thanks for reporting this issue @kafleg!

Test Report

Env

• WordPress 5.9-beta1-52296-src
• Chrome 96.0.4664.45
• Windows 10
• Theme: Twenty Twenty Two
• Gutenberg Editor
• Plugin: None activated

Steps to test

1. Navigate to Appearance > Editor.
2. Navigate to Template Parts.

Results

The reported notice is displayed:

Notice: Undefined index: path in <path>/src/wp-includes/rest-api.php on line 2854

Notes

• This is caused by the ?context=edit path missing a leading slash.
• When a leading slash is added, the notice no longer appears.

[costdev]

Adds a leading slash to paths without one.

[costdev]

Patch updated to remove new error by covering paths of array type.

[mukesh27]

Hi there!

In addition to the error, I also see the below error in my error log.

PHP Warning:  array_keys() expects parameter 1 to be array, bool given in /wordpress/wp-includes/update.php on line 993
PHP Warning:  Invalid argument supplied for foreach() in /wordpress/wp-includes/update.php on line 993

This PR:

• Covers $path values of type string.
• Covers $path values of type array with values of type string.
• Adds unit tests.

Trac ticket: https://core.trac.wordpress.org/ticket/54558

[costdev]

@mukesh27 To make sure this doesn't occur at an earlier stage, can you do the following:

1. Navigate to Appearance > Editor.
2. Clear your debug.log file.
3. Navigate to Template Parts.
4. Confirm that the log now contains the error you mentioned above.

[audrasjb]

Self assigning for test/review.

[mukesh27]

If I follow the below steps I don't get additional errors that I post.

Replying to costdev:

1. Navigate to Appearance > Editor.
2. Clear your debug.log file.
3. Navigate to Template Parts.
4. Confirm that the log now contains the error you mentioned above.

[Boniu91]

Test Report

Env

• WordPress 5.0.14 and 5.9-beta1
• Ubuntu 20.04.2 LTS server
• Theme: Twenty Twenty One
• Plugin: WP Downgrade | Beta Tester

Steps to test

1. Navigate to Appearance > Editor.
2. Clear your debug.log file.
3. Navigate to Template Parts.

No error in debug.log nor on the frontend.

[audrasjb]

It looks good to me as well.
As the two previous tests were successful, let's commit the last patch.

[audrasjb]

In 52312:

Editor: Avoid undefined index notices in the Template Parts Editor.

This changes adds a leading slash when needed in the ?context=edit path to avoid an undefined index notice in the Template Parts Editor.

Follow-up to [52275].

Props kafleg, costdev, mukesh27, Boniu91.
Fixes #54558.

Committed in https://core.trac.wordpress.org/changeset/52312

[audrasjb]

In 52313:

Coding standards: Address a few coding standards issues after [52312].

Follow-up to [52312].

See #54558.

[costdev]

#54576 was marked as a duplicate.

[TobiasBg]

[52312] added a foreach loop with the value being assigned by reference.
This can lead to weird issues later on, if the variable (here: $path) is used again in the function, while the reference was not broken. While it's not in this case, let's follow best practices and add unset( $path ); after the loop.

See e.g. the example at ​https://www.php.net/manual/en/control-structures.foreach.php

[SergeyBiryukov]

In 52322:

Coding Standards: Break the $path reference after a foreach loop in block_editor_rest_api_preload().

When using a foreach loop with a value assigned by reference, the variable continues to point to the last array element even after the loop, so it is recommended to destroy it by unset() to avoid unexpected behavior later on.

See ​PHP Manual: foreach.

Follow-up to [52312], [52313].

Props TobiasBg.
See #54558.