Add simple predicate functions

[mabdullahsari]

Disclaimer: I'm not really sure about the placing of the new trait and its naming. I'm prepared to carry out any changes as requested. Thanks!

The proposed predicate functions in this PR already exist as query scopes within HasRecursiveRelationshipScopes. However, it would be nice to also have them as instance methods on the models itself. I haven't gone overboard and re-implemented every single one as predicates, but these simple ones are IMHO the most useful ones.

---

Assume the following scenario:

class PageController
{
    public function __invoke(Page $page)
    {
        return View::make('editorialPage', [
            'crumbs' => $this->getBreadcrumbs($page),
            'page' => $page,
        ]);
    }

    private function getBreadcrumbs(Page $page): Collection
    {
        if ($page->isRoot()) {
            return Collection::make([]);
        }

        $page->load('ancestors:id,parent_id,title,slug,path');

        return $page->ancestors->reverse()->values()->push($page);
    }
}

• The page model, which represents a dynamic page on a website, is always loaded regardless of its relationship status.
• A breadcrumb trail is generated if, and only if, the page is not a root and thus has ancestors which is then eager loaded.

[staudenmeir]

Thanks, I'll take a look.

[mabdullahsari]

Thanks, I'll take a look.

Seems like some tests are failing, and rightfully so.
I totally forgot about Eloquent delegating to the QueryBuilder if you do something like Category::isRoot()->get().

I'm not really sure if this fixable as it will probably require a new major release in this case. 😕

[mabdullahsari]

I think the only possible "fix" in this case is moving the Predicates trait out of the base trait and making it opt-in in userland code. There is no real solution to this problem without introducing a breaking change, I'm afraid.