[6.x] Add an eager() method to the lazy collection class (laravel#2…

…9832)

* Add a cache() method to the lazy collection class

* Rename `cache` method to `eager`

src/Illuminate/Support/LazyCollection.php

@@ -99,6 +99,16 @@ public function all()
         return iterator_to_array($this->getIterator());
     }
 
+    /**
+     * Eager load all items into a new lazy collection backed by an array.
+     *
+     * @return static
+     */
+    public function eager()
+    {
+        return new static($this->all());
+    }
+
     /**
      * Get the average value of a given key.
      *

tests/Support/SupportLazyCollectionIsLazyTest.php

@@ -8,6 +8,16 @@
 
 class SupportLazyCollectionIsLazyTest extends TestCase
 {
+    public function testEagerEnumeratesOnce()
+    {
+        $this->assertEnumeratesOnce(function ($collection) {
+            $collection = $collection->eager();
+
+            $collection->count();
+            $collection->all();
+        });
+    }
+
     public function testChunkIsLazy()
     {
         $this->assertDoesNotEnumerate(function ($collection) {

tests/Support/SupportLazyCollectionTest.php

@@ -67,6 +67,19 @@ public function testCanCreateCollectionFromClosure()
         ], $data->all());
     }
 
+    public function testEager()
+    {
+        $source = [1, 2, 3, 4, 5];
+
+        $data = LazyCollection::make(function () use (&$source) {
+            yield from $source;
+        })->eager();
+
+        $source[] = 6;
+
+        $this->assertSame([1, 2, 3, 4, 5], $data->all());
+    }
+
     public function testTapEach()
     {
         $data = LazyCollection::times(10);