Chained properties result in errors if TemplateGlobalProvider returns null

[GuySartorelli]

Module version(s) affected

>= 5.0.0

Description

If a method in a TemplateGlobalProvider returns null, and you chain properties from it, the following error results:

Uncaught Error: Call to a member function obj() on null

Relevant stack trace:

SilverStripe\View\SSViewer_Scope->getObj(Hmm, , 1, )
SSViewer_DataPresenter.php:298

SilverStripe\View\SSViewer_DataPresenter->getObj(Hmm, , 1, )
SSViewer_Scope.php:218

SilverStripe\View\SSViewer_Scope->obj(Hmm, , 1, )
SSViewer_DataPresenter.php:285

SilverStripe\View\SSViewer_DataPresenter->obj(Hmm, , 1)
.cachethemes.simple.templates.Layout.Page.ss:26

include(/var/www/html/silverstripe-cache/gsartorelli/.cachethemes.simple.templates.Layout.Page.ss)
SSViewer.php:576

SilverStripe\View\SSViewer->includeGeneratedTemplate(/var/www/html/silverstripe-cache/gsartorelli/.cachethemes.simple.templates.Layout.Page.ss, PageController, , Array, )
SSViewer.php:648

SilverStripe\View\SSViewer->process(PageController, )
SSViewer.php:642

This seems to be a result of d6e8229 which was originally added in #8456 and rescued from the master branch in #10497

Based on the docs change that was made along side this, it looks like it was intended to be only for passing arguments around, not for intermediate obj() calls.

How to reproduce

Add this TemplateGlobalProvider

<?php

use SilverStripe\View\TemplateGlobalProvider;

class TemplateProvider implements TemplateGlobalProvider
{
    public static function getNullProperty()
    {
        return null;
    }

    public static function get_template_global_variables()
    {
        return ['NullProperty' => 'getNullProperty'];
    }
}

Then add this to any template:

$NullProperty.Hmm.Ohno

Possible Solution

No response

Additional Context

This is a regression - in CMS 4 the null resulted in simply nothing returning in the template (which is how all other null is treated in the template layer).

Validations

• Check that there isn't already an issue that reports the same bug
• Double check that your reproduction steps work in a fresh installation of silverstripe/installer (with any code examples you've provided)

PRs

• FIX Don't error if template global is null #11331