Restrict Available Gutenberg Blocks Based on User Role

/**
 * Restrict available Gutenberg blocks based on user roles.
 */
add_filter(
	'allowed_block_types_all',
	'alkesh_restrict_gutenberg_blocks_by_role',
	20,
	2
);

function alkesh_restrict_gutenberg_blocks_by_role(
	$allowed_block_types,
	$editor_context
) {
	// Allow administrators to use all available blocks.
	if ( current_user_can( 'manage_options' ) ) {
		return $allowed_block_types;
	}

	$user = wp_get_current_user();

	if ( empty( $user->roles ) ) {
		return $allowed_block_types;
	}

	/*
	 * Configure allowed blocks for each user role.
	 * Use null to allow all blocks for a particular role.
	 */
	$role_blocks = array(
		'editor' => null,

		'author' => array(
			'core/paragraph',
			'core/heading',
			'core/image',
			'core/list',
			'core/list-item',
			'core/quote',
			'core/separator',
			'core/spacer',
		),

		'contributor' => array(
			'core/paragraph',
			'core/heading',
			'core/list',
			'core/list-item',
			'core/quote',
		),

		'subscriber' => array(),
	);

	$allowed_for_user = array();

	foreach ( $user->roles as $role ) {
		if ( ! array_key_exists( $role, $role_blocks ) ) {
			continue;
		}

		// A role with null configuration has unrestricted block access.
		if ( null === $role_blocks[ $role ] ) {
			return $allowed_block_types;
		}

		$allowed_for_user = array_merge(
			$allowed_for_user,
			$role_blocks[ $role ]
		);
	}

	// Remove duplicate block names.
	$allowed_for_user = array_unique( $allowed_for_user );

	// Respect restrictions applied by other filters.
	if ( false === $allowed_block_types ) {
		return false;
	}

	if ( is_array( $allowed_block_types ) ) {
		$allowed_for_user = array_intersect(
			$allowed_for_user,
			$allowed_block_types
		);
	}

	return array_values( $allowed_for_user );
}