isFirst()/isLast() methods doesn't work properly when use listed(), published(), unlisted() methods

Describe the bug The isFirst() and isLast() method doesn't work if I use methods such as listed(), published(), unlisted(), and only one element when retrieving child elements of a collection.

First Sample

$children = new Pages([
    new Page(['slug' => 'a']),
    new Page(['slug' => 'b', 'num' => 1]),
    new Page(['slug' => 'c'])
]);

$parent = new Page(['slug' => 'a', 'children' => $children->toArray()]);

foreach ($parent->children()->listed() as $page) {
    if ($page->isFirst()) {
        echo "First page is " . $page->slug() . ":" . $page->status() . "\n";
    }
    else if ($page->isLast()) {
        echo "Last page is " . $page->slug() . ":" . $page->status() . "\n";
    }
    else {
        echo "Page is " . $page->slug() . ":" . $page->status() . "\n";
    }
}

You will see: "Page is b:listed"

Expected behavior Output should be: "First page is b:listed"

Second Sample

Another example with two listed items

$children = new Pages([
    new Page(['slug' => 'a']),
    new Page(['slug' => 'b', 'num' => 1]),
    new Page(['slug' => 'c', 'num' => 2])
]);

You will see if you use children()->listed() method

Page is b:listed Last page is c:listed

Expected output:

First page is b:listed Last page is c:listed

Third Sample

Lets look out last sample with four items and two listed in middle of collection:

$children = new Pages([
    new Page(['slug' => 'a']),
    new Page(['slug' => 'b', 'num' => 1]),
    new Page(['slug' => 'c', 'num' => 2]),
    new Page(['slug' => 'd'])
]);

You will see if you use children()->listed() method

Page is b:listed Page is c:listed

Expected output for this sample:

First page is b:listed Last page is c:listed

I guess this issue about siblingsCollection() method: https://github.com/getkirby/kirby/blob/80b69380e672565a849037232c9951d1e32774c8/src/Cms/PageSiblings.php#L178-L185

Kirby Version 3.2.2

Thanks as always for the detailed bug report!

It's indeed the method you linked to. Unfortunately this issue is very hard to fix as the model (here: page object) doesn't know what collection it was returned from. The only way we could fix this is to create clones of the model objects every time a collection is created. Each clone would then store the actual collection it came from. This would however be a massive performance hit and the RAM usage would increase by a lot because of all the additional objects PHP would need to keep in memory.

You can get around this issue like so:

$children = new Pages([
    new Page(['slug' => 'a']),
    new Page(['slug' => 'b', 'num' => 1]),
    new Page(['slug' => 'c'])
]);

$parent = new Page(['slug' => 'a', 'children' => $children->toArray()]);

$collection = $parent->children()->listed();
foreach ($collection as $page) {
    if ($collection->first()->is($page)) {
        echo "First page is " . $page->slug() . ":" . $page->status() . "\n";
    }
    else if ($collection->last()->is($page)) {
        echo "Last page is " . $page->slug() . ":" . $page->status() . "\n";
    }
    else {
        echo "Page is " . $page->slug() . ":" . $page->status() . "\n";
    }
}

Not entirely as clean, sure, but a lot better performance-wise.

Closing this issue because we can't really fix it. If you have an idea, feel free to reopen. :)

I understand very well 👍

I think $collection->first()->is($page) and $collection->last()->is($page) ideas are great!

I love that you always come up with a solution ❤️

Also if the new extension type that collection methods comes, I think we will solve it in a shorter way :))

I implemented to pagesMethod as your idea for now.

Thank you for your interest

Several pieces of code to help:

Kirby::plugin('my/pagesMethods', [
    'pagesMethods' => [
        'isReallyFirst' => function (\Kirby\Cms\Page $page) {
            return $this->first()->is($page);
        },
        'isReallyLast' => function (\Kirby\Cms\Page $page) {
            return $this->last()->is($page);
        }
    ]
]);

Usage:

foreach ($pages as $page) {
    if ($pages->isReallyFirst($page)) {
        echo "First page";
    }
}

getkirby / kirby