How to add new panel under “document” in Gutenberg

Question

I am trying to add a new component panel under document tab, like categories, featured image etc.

Answer 1

add_meta_box will do the trick, but only if you add the context-argument with a value of 'side':

add_meta_box(
    'box-id-here',
    'Box Title Here',
    'createBoxHtml',
    'post',
    'side' ); // <-- this is important

Arrrh, two days for nothing!

---

Old answer

According to this tutorial, we can add our custom sidebar and fill it with customized form inputs.

Here is a working example in a React JSX version. This adds a meta field country:

const { registerPlugin } = wp.plugins;
const { PluginSidebar } = wp.editPost;
const { TextControl } = wp.components;
const { withSelect, withDispatch } = wp.data;

// Customized TextControl
const CustomMetaField = withDispatch( ( dispatch, props ) => {
    return {
        updateMetaValue: ( v ) => {
            dispatch( 'core/editor' ).editPost( {
                meta: {
                    [ props.metaFieldName ]: v
                }
            });
        }
    };
})( withSelect( ( select, props ) => {
    return {
        [ props.metaFieldName ]: select( 'core/editor' ).getEditedPostAttribute( 'meta' )[ props.metaFieldName ]
    };
} )( ( props ) => (
    <TextControl
        value={props[ props.metaFieldName ] }
        label="Country"
        onChange={( v ) => {
            props.updateMetaValue( v );
        }}
    /> )
) );


// Our custom sidebar
registerPlugin( 'custom-sidebar', {
    render() {
        return (
            <PluginSidebar
                name="project-meta-sidebar"
                title="Project Meta">
                <div className="plugin-sidebar-content">
                    <CustomMetaField metaFieldName="country" />
                </div>
            </PluginSidebar>
        );
    },
} );

And in PHP, register the meta field in the init-hook:

register_meta( 'post', 'country', [
    'show_in_rest' => TRUE,
    'single' => TRUE,
    'type' => 'string'
] );

I know:

This is still not the required solution, but nearly.

Answer 2

They've added the PluginDocumentSettingPanel SlotFill now.

const { registerPlugin } = wp.plugins
const { PluginDocumentSettingPanel } = wp.editPost
 
const PluginDocumentSettingPanelDemo = () => (
    <PluginDocumentSettingPanel
        name="custom-panel"
        title="Custom Panel"
        className="custom-panel"
    >
        Custom Panel Contents
    </PluginDocumentSettingPanel>
)
registerPlugin('plugin-document-setting-panel-demo', {
    render: PluginDocumentSettingPanelDemo
})

Answer 3

add_meta_box adds a new panel there for the gutenberg editor

Answer 4

You can add this code to your function.php. This code create new tab and add text field to this tab. Text field save to database like custom field in post_meta table and you can output this like default WP post meta.
1. Create tab Настройки UTM.
2. Create custom text field utm_post_class
3. To output in website use $utm = get_post_meta( $post->ID, 'utm_post_class', true );

//Article UTM Link
add_action( 'load-post.php', 'utm_post_meta_boxes_setup' );
add_action( 'load-post-new.php', 'utm_post_meta_boxes_setup' );

function utm_post_meta_boxes_setup() {
    add_action( 'add_meta_boxes', 'utm_add_post_meta_boxes' );
    add_action( 'save_post', 'utm_save_post_class_meta', 10, 2 );
}

function utm_add_post_meta_boxes() {
    add_meta_box(
        'utm-post-class',
        'Настройки UTM',
        'utm_post_class_meta_box',
        'post',
        'side',
        'default'
    );
}

function utm_post_class_meta_box( $post ) {
    wp_nonce_field( basename( __FILE__ ), 'utm_post_class_nonce' );?>

    <div class="components-base-control editor-post-excerpt__textarea">
        <div class="components-base-control__field">
            <label class="components-base-control__label" for="utm-post-class">UTM ссылка (необязательно)</label>
            <input type="text" name="utm-post-class" id="utm-post-class" class="edit-post-post-schedule" value="<?php echo esc_attr( get_post_meta( $post->ID, 'utm_post_class', true ) ); ?>">
        </div>
    </div>
<?php }

function utm_save_post_class_meta( $post_id, $post ) {

    if ( !isset( $_POST['utm_post_class_nonce'] ) || !wp_verify_nonce( $_POST['utm_post_class_nonce'], basename( __FILE__ ) ) )
        return $post_id;

    $post_type = get_post_type_object( $post->post_type );
    if ( !current_user_can( $post_type->cap->edit_post, $post_id ) )
        return $post_id;

    $new_meta_value = ( isset( $_POST['utm-post-class'] ) ? $_POST['utm-post-class'] : '' );
    $meta_key = 'utm_post_class';
    $meta_value = get_post_meta( $post_id, $meta_key, true );

    if ( $new_meta_value && '' == $meta_value )
        add_post_meta( $post_id, $meta_key, $new_meta_value, true );
    elseif ( $new_meta_value && $new_meta_value != $meta_value )
        update_post_meta( $post_id, $meta_key, $new_meta_value );
    elseif ( '' == $new_meta_value && $meta_value )
        delete_post_meta( $post_id, $meta_key, $meta_value );
}