Merge sub properties in `add_post_type_support()`. #10426

fabiankaegy · 2025-10-27T22:45:30Z

Previously, calling add_post_type_support() multiple times for the same post type and feature with array arguments would overwrite the previous arguments instead of merging them. This prevented plugins and themes from incrementally adding sub-properties to the same feature.

This changes the behavior to merge associative array arguments when the function is called multiple times with the same post type and feature combination.

Example usage:

add_post_type_support( 'page', 'editor', array(
    'default-mode' => 'template-locked',
) );

add_post_type_support( 'page', 'editor', array(
    'block-comments' => true,
) );

// Both properties are now preserved instead of only the last one.

The fix maintains full backwards compatibility by only merging when both the existing and new values are associative arrays. All other calling patterns continue to work as before.

Props @fabiankaegy, @Mamaduka, @t-hamano .

Trac ticket: https://core.trac.wordpress.org/ticket/64156#ticket

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

Previously, calling `add_post_type_support()` multiple times for the same post type and feature with array arguments would overwrite the previous arguments instead of merging them. This prevented plugins and themes from incrementally adding sub-properties to the same feature. This changes the behavior to merge associative array arguments when the function is called multiple times with the same post type and feature combination. Example usage: {{{ add_post_type_support( 'page', 'editor', array( 'default-mode' => 'template-locked', ) ); add_post_type_support( 'page', 'editor', array( 'block-comments' => true, ) ); // Both properties are now preserved instead of only the last one. }}} The fix maintains full backwards compatibility by only merging when both the existing and new values are associative arrays. All other calling patterns continue to work as before. Props fabiankaegy, mamaduka, wildworks.

github-actions · 2025-10-27T22:45:42Z

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Core Committers: Use this line as a base for the props when committing in SVN:

Props fabiankaegy, wildworks, adamsilverstein, mamaduka, mindctrl, westonruter, johnjamesjacoby.

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github-actions · 2025-10-27T23:10:04Z

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adamsilverstein

Nice!

src/wp-includes/post.php

Mamaduka · 2025-10-28T19:29:04Z

IMO, the current behavior is broken, but given everything WP, would this be considered a breaking change?

cc @desrosj, @peterwilsoncc

Co-authored-by: Mamaduka <[email protected]>

src/wp-includes/post.php

westonruter · 2025-11-03T19:47:47Z

src/wp-includes/post.php

+			if ( isset( $_wp_post_type_features[ $post_type ][ $feature ][0] )
+				&& is_array( $_wp_post_type_features[ $post_type ][ $feature ][0] )
+				&& isset( $args[0] )
+				&& is_array( $args[0] ) ) {


The is_array( $args[0] ) call here isn't checking whether the arg is an associative array. Shouldn't it also check if ! isset( $args[0][0] )?

Or rather: ! array_is_list( $args[0] )

Additionally, what if someone tries to merge an empty array? Should that be allowed? So perhaps the new check here should be: ! array_is_list( $args[0] ) || empty( $args[0] )

westonruter · 2025-11-03T19:51:51Z

src/wp-includes/post.php

-			$_wp_post_type_features[ $post_type ][ $feature ] = $args;
+			// Check if feature already exists with args and if both are associative arrays that should be merged.
+			if ( isset( $_wp_post_type_features[ $post_type ][ $feature ][0] )
+				&& is_array( $_wp_post_type_features[ $post_type ][ $feature ][0] )


Per below, should this check to make sure it is actually an associative array? I think it should add this check: ! array_is_list( $_wp_post_type_features[ $post_type ][ $feature ][0] )

Co-authored-by: Weston Ruter <[email protected]>

t-hamano · 2025-11-07T10:38:28Z

The RC1 release is approaching, so we need to decide whether or not to ship this pull request. What do you think?

src/wp-includes/post.php

westonruter · 2025-11-07T21:33:47Z

tests/phpunit/tests/post/types.php

+	 *
+	 * @ticket 64156
+	 */
+	public function test_add_post_type_support_merges_array_arguments() {


TODO: Also add tests for theme features merging non-associative arrays.

Co-authored-by: Weston Ruter <[email protected]>

t-hamano · 2025-11-10T02:59:56Z

This pull request seems very robust, but my only concern is that it behaves differently from remove_post_type_support(). Currently, the remove_post_type_support() function shouldn't be able to remove only sub-features. What do you think?

westonruter · 2025-11-10T04:36:21Z

This pull request seems very robust, but my only concern is that it behaves differently from remove_post_type_support(). Currently, the remove_post_type_support() function shouldn't be able to remove only sub-features. What do you think?

For completeness it seems that being able to remove sub-features via remove_post_type_support() makes sense. I don't know how common of a need it is, however. So this would entail adding a new $args param to remove_post_type_support() to match add_post_type_support():

function add_post_type_support( $post_type, $feature, ...$args )

So:

function remove_post_type_support( $post_type, $feature, ...$args )

But how would this be used? If $args[0] is an associative array, would it remove the supplied keys only if the values match? That would be the case if using array_diff(). But what if the user wants to remove the sub-feature regardless of the value?

t-hamano · 2025-11-10T06:13:20Z

For completeness it seems that being able to remove sub-features via remove_post_type_support() makes sense. I don't know how common of a need it is,

I believe this need exists because the editor feature now has multiple sub-futures.

Consider a scenario where multiple sub-functions are registered as shown below, and you want to disable only the 'notes' sub-feature:

add_post_type_support( 'custom', 'editor', array(
    'default-mode' => 'template-locked',
    'notes'        => true,
) );

You will need to remove the existing main feature and then register the necessary sub-feature again, as follows.

remove_post_type_support( 'custom', 'editor' );
add_post_type_support( 'custom', 'editor', array(
    'default-mode' => 'template-locked',
) );

I don't think this concern will be a blocker here, but I wanted to share it just in case.

JJJ · 2025-11-11T05:50:05Z

Consider also that $feature could be an array and $args gets set to all of them...

add_post_type_support( 'post', array( 'title', 'author' ), array( 'jjj' => 'cool' ) );

...and that remove_post_type_support() only supports removing a single $feature, so there already is not parity between them.

I think using $args as sub-features was not a great idea for the reasons highlighted by the discussion here, and that every sub-feature should be a $feature with a unique key with its own (or no) arguments.

Is it too late to create a new feature key instead?

Mamaduka · 2025-11-11T14:25:32Z

Consider also that $feature could be an array and $args gets set to all of them

I think this was/is an "issue" even without this patch.

remove_post_type_support() only supports removing a single $feature, so there already is not parity between them.

Agreed, it makes sense to have feature parity here. We should also update post_type_supports and allow checking sub-features.

I think using $args as sub-features was not a great idea for the reasons highlighted by the discussion here, and that every sub-feature should be a $feature with a unique key with its own (or no) arguments.

Initially, it was implemented this way, but we changed it later, since these are the actual sub-features for editor. Notes won't work without editor support.

cc @swissspidy

swissspidy · 2025-11-11T14:30:29Z

src/wp-includes/post.php

 * @since 3.0.0
 * @since 5.3.0 Formalized the existing and already documented `...$args` parameter
 *              by adding it to the function signature.
+ * @since 6.9.0 Multiple calls to add support for the same feature with array


As per my comment on the ticket, I'd say this is something for 7.0. It's an enhancement and could have unintended side effects for people who relied on the previous behavior, and we're about to publish RC1.

swissspidy · 2025-11-11T14:32:14Z

tests/phpunit/tests/post/types.php

+		$this->assertTrue( $support['editor'][0]['block-comments'] );
+		$this->assertSame( 'test-value', $support['editor'][0]['another-option'] );
+
+		_unregister_post_type( 'foo' );


Just noting that this code will never run if any of the above assertions fails. Best to move this to tear_down() or restructure the test to call this before the assertions.

swissspidy · 2025-11-11T14:33:25Z

tests/phpunit/tests/post/types.php

+		);
+
+		$support = get_all_post_type_supports( 'foo' );
+		$this->assertIsArray( $support['editor'] );


The best practice in core is to add custom assertion messages (the last argument) when a test contains numerous assertions. Makes it much easier to debug a failing test and figuring out which assertion is actually failing.

fabiankaegy added 2 commits October 27, 2025 23:41

Add tests for 64156

0aa95a8

Mamaduka requested review from Mamaduka and adamsilverstein October 28, 2025 04:11

adamsilverstein approved these changes Oct 28, 2025

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Mamaduka reviewed Oct 28, 2025

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