LazyCollection from iterator without converting to array underneath?

[crissi]

I know we do not allow generators as direct input to lazyCollection. Is the same problem with iterators?

It seems that the whole iterator is converted to an array when you use new LazyCollection.

Could we not allow iterators as input without converting it to an array?

[erikgaal]

Hi @crissi,

You can actually start a LazyCollection with a generator function, like so:

LazyCollection::make(function () {
    $number = 1;
	while (true) {
    	yield $number++;
    }
});

[crissi]

i know. But I was thinking it could do it automatically when given an iterator.

So I am thinking this code in EnumeratesValues:

could be replaced with this:

     elseif ($items instanceof Traversable) {
         return function() use ($items) {
              foreach ($items as $row) {
                   yield $row;
               }
         });

    }

[erikgaal]

But that function needs to return an array. It's exactly when you want to convert from an iterator to an array.

[crissi]

ahh okay, could it add to the the lazyCollection constructor instead.

[Anticom]

IMHO @crissi has a point here.

All terminal operations on the LazyCollection such as each, combine or zip make use of makeIterator which already supports IteratorAggregate (but not Iterator for some reason?)

If we don't look at the getArrayableItems but the ctor directly we could add support for IteratorAggregate(and possibly also Iterator as such:

    public function __construct($source = null)
    {
        if ($source instanceof Closure || $source instanceof IteratorAggregate /*|| $source instanceof Iterator*/ || $source instanceof self) {
            $this->source = $source;
        } elseif (is_null($source)) {
            $this->source = static::empty();
        } elseif ($source instanceof Generator) {
            throw new InvalidArgumentException(
                'Generators should not be passed directly to LazyCollection. Instead, pass a generator function.'
            );
        } else {
            $this->source = $this->getArrayableItems($source);
        }
    }

NB: With the advent of match expressions in PHP 8.0 and current stable version of Laravel framework requiring "php": "^8.2" anyways, this could be written a bit more readable IMHO:

    public function __construct($source = null)
    {
        $this->source = match(true) {
            $source instanceof Closure,
            $source instanceof IteratorAggregate,
            // In case we want & can support Iterator. (May be subsituted with checking for Traversable, if both Iterator & IteratorAggregate can be supported.)
            // $source instanceof Iterator,
            $source instanceof self => $source,
            is_null($source) =>  static::empty(),
            $source instanceof Generator => throw new InvalidArgumentException('Generators should not be passed directly to LazyCollection. Instead, pass a generator function.'),
            default => $this->getArrayableItems($source),
        };
    }

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If a maintainer stumbles across this, lkm whether you'd be open for a PR. I'd be more than happy to contribute!