Implements Collection::compact() operation.

docs/pages/api.rst

@@ -297,6 +297,20 @@ Signature: ``Collection::combine(...$keys);``
     $collection = Collection::with(['a', 'b', 'c', 'd'])
         ->combine('w', 'x', 'y', 'z')
 
+compact
+~~~~~~~
+
+Remove all the null values from the collection.
+
+Interface: `Compactable`_
+
+Signature: ``Collection::compact();``
+
+.. code-block:: php
+
+    $collection = Collection::with(['a', 1 => 'b', null, false, 0, 'c'];)
+        ->combine();
+
 cycle
 ~~~~~
 
@@ -1129,6 +1143,7 @@ Interface: `Truthyable`_
 .. _Columnable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Columnable.php
 .. _Combinateable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Combinateable.php
 .. _Combineable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Combineable.php
+.. _Compactable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Compactable.php
 .. _Containsable: https://github.com/loophp/collection/blob/master/src/Contract/Transformation/Containsable.php
 .. _Cycleable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Cycleable.php
 .. _Distinctable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Distinctable.php

spec/loophp/collection/CollectionSpec.php

@@ -372,6 +372,15 @@ public function it_can_combine(): void
             ->during('all');
     }
 
+    public function it_can_compact(): void
+    {
+        $input = ['a', 1 => 'b', null, false, 0, 'c'];
+
+        $this::fromIterable($input)
+            ->compact()
+            ->shouldIterateAs(['a', 1 => 'b', 3 => false, 4 => 0, 5 => 'c']);
+    }
+
     public function it_can_contains(): void
     {
         $this::fromIterable(range('A', 'C'))

src/Collection.php

@@ -18,6 +18,7 @@
 use loophp\collection\Operation\Column;
 use loophp\collection\Operation\Combinate;
 use loophp\collection\Operation\Combine;
+use loophp\collection\Operation\Compact;
 use loophp\collection\Operation\Cycle;
 use loophp\collection\Operation\Distinct;
 use loophp\collection\Operation\Explode;
@@ -120,6 +121,11 @@ public function combine(...$keys): BaseInterface
         return $this->run(new Combine(...$keys));
     }
 
+    public function compact(): BaseInterface
+    {
+        return $this->run(new Compact());
+    }
+
     public function contains($key): bool
     {
         return $this->transform(new Contains($key));

src/Contract/Collection.php

@@ -12,6 +12,7 @@
 use loophp\collection\Contract\Operation\Columnable;
 use loophp\collection\Contract\Operation\Combinateable;
 use loophp\collection\Contract\Operation\Combineable;
+use loophp\collection\Contract\Operation\Compactable;
 use loophp\collection\Contract\Operation\Cycleable;
 use loophp\collection\Contract\Operation\Distinctable;
 use loophp\collection\Contract\Operation\Explodeable;
@@ -79,6 +80,7 @@ interface Collection extends
     Columnable,
     Combinateable,
     Combineable,
+    Compactable,
     Containsable,
     Cycleable,
     Distinctable,

src/Contract/Operation/Compactable.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Contract\Operation;
+
+use loophp\collection\Contract\Base;
+
+interface Compactable
+{
+    /**
+     * Combine a collection of items with some other keys.
+     *
+     * @return \loophp\collection\Base|\loophp\collection\Contract\Collection
+     */
+    public function compact(): Base;
+}

src/Operation/Compact.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Operation;
+
+use Closure;
+use Generator;
+use loophp\collection\Contract\Operation;
+use loophp\collection\Transformation\Run;
+
+final class Compact extends AbstractOperation implements Operation
+{
+    public function __invoke(): Closure
+    {
+        return static function (iterable $collection): Generator {
+            return yield from
+            (new Run(
+                new Filter(
+                    static function ($item): bool {
+                        return null !== $item;
+                    }
+                )
+            )
+            )($collection);
+        };
+    }
+}