ld match the default ones and
		 * affect the generated CSS.
		 */
		if ( isset( $old['settings']['typography']['fontSizes'] ) ) {
			$new['settings']['typography']['defaultFontSizes'] = false;
		}

		/*
		 * Similarly to defaultFontSizes, we need to migrate defaultSpacingSizes
		 * as it controls the PRESETS_METADATA prevent_override which was
		 * previously hardcoded to false. This only needs to happen when the
		 * theme provided spacing sizes via spacingSizes or spacingScale.
		 */
		if (
			isset( $old['settings']['spacing']['spacingSizes'] ) ||
			isset( $old['settings']['spacing']['spacingScale'] )
		) {
			$new['settings']['spacing']['defaultSpacingSizes'] = false;
		}

		/*
		 * In v3 spacingSizes is merged with the generated spacingScale sizes
		 * instead of completely replacing them. The v3 behavior is what was
		 * documented for the v2 schema, but the code never actually did work
		 * that way. Instead of surprising users with a behavior change two
		 * years after the fact at the same time as a v3 update is introduced,
		 * we'll continue using the "bugged" behavior for v2 themes. And treat
		 * the "bug fix" as a breaking change for v3.
		 */
		if ( isset( $old['settings']['spacing']['spacingSizes'] ) ) {
			unset( $new['settings']['spacing']['spacingScale'] );
		}

		return $new;
	}

	/**
	 * Processes the settings subtree.
	 *
	 * @since 5.9.0
	 *
	 * @param array $settings        Array to process.
	 * @param array $paths_to_rename Paths to rename.
	 *
	 * @return array The settings in the new format.
	 */
	private static function rename_paths( $settings, $paths_to_rename ) {
		$new_settings = $settings;

		// Process any renamed/moved paths within default settings.
		self::rename_settings( $new_settings, $paths_to_rename );

		// Process individual block settings.
		if ( isset( $new_settings['blocks'] ) && is_array( $new_settings['blocks'] ) ) {
			foreach ( $new_settings['blocks'] as &$block_settings ) {
				self::rename_settings( $block_settings, $paths_to_rename );
			}
		}

		return $new_settings;
	}

	/**
	 * Processes a settings array, renaming or moving properties.
	 *
	 * @since 5.9.0
	 *
	 * @param array $settings        Reference to settings either defaults or an individual block's.
	 * @param array $paths_to_rename Paths to rename.
	 */
	private static function rename_settings( &$settings, $paths_to_rename ) {
		foreach ( $paths_to_rename as $original => $renamed ) {
			$original_path = explode( '.', $original );
			$renamed_path  = explode( '.', $renamed );
			$current_value = _wp_array_get( $settings, $original_path, null );

			if ( null !== $current_value ) {
				_wp_array_set( $settings, $renamed_path, $current_value );
				self::unset_setting_by_path( $settings, $original_path );
			}
		}
	}

	/**
	 * Removes a property from within the provided settings by its path.
	 *
	 * @since 5.9.0
	 *
	 * @param array $settings Reference to the current settings array.
	 * @param array $path Path to the property to be removed.
	 */
	private static function unset_setting_by_path( &$settings, $path ) {
		$tmp_settings = &$settings;
		$last_key     = array_pop( $path );
		foreach ( $path as $key ) {
			$tmp_settings = &$tmp_settings[ $key ];
		}

		unset( $tmp_settings[ $last_key ] );
	}
}