Add throttle method to LazyCollection

src/Illuminate/Collections/LazyCollection.php

@@ -1570,6 +1570,28 @@ public function tapEach(callable $callback)
         });
     }
 
+    /**
+     * Throttle the values, releasing them at most once per the given seconds.
+     * 
+     * @return static<TKey, TValue>
+     */
+    public function throttle(float $seconds)
+    {
+        return new static(function () use ($seconds) {
+            $microseconds = $seconds * 1_000_000;
+
+            foreach ($this as $key => $value) {
+                $fetchedAt = $this->preciseNow();
+
+                yield $key => $value;
+
+                $sleep = $microseconds - ($this->preciseNow() - $fetchedAt);
+
+                $this->usleep((int) $sleep);
+            }
+        });
+    }
+
     /**
      * Flatten a multi-dimensional associative array with dots.
      *
@@ -1781,4 +1803,32 @@ protected function now()
             ? Carbon::now()->timestamp
             : time();
     }
+
+    /**
+     * Get the precise current time.
+     *
+     * @return float
+     */
+    protected function preciseNow()
+    {
+        return class_exists(Carbon::class)
+            ? Carbon::now()->getPreciseTimestamp()
+            : microtime(true) * 1_000_000;
+    }
+
+    /**
+     * Sleep for the given amount of microseconds.
+     * 
+     * @return void
+     */
+    protected function usleep(int $microseconds)
+    {
+        if ($microseconds <= 0) {
+            return;
+        }
+
+        class_exists(Sleep::class)
+            ? Sleep::usleep($microseconds)
+            : usleep($microseconds);
+    }
 }

tests/Support/SupportLazyCollectionIsLazyTest.php

@@ -7,6 +7,7 @@
 use Illuminate\Support\ItemNotFoundException;
 use Illuminate\Support\LazyCollection;
 use Illuminate\Support\MultipleItemsFoundException;
+use Illuminate\Support\Sleep;
 use Mockery as m;
 use PHPUnit\Framework\TestCase;
 use stdClass;
@@ -1370,6 +1371,25 @@ public function testTapEachIsLazy()
         });
     }
 
+    public function testThrottleIsLazy()
+    {
+        Sleep::fake();
+
+        $this->assertDoesNotEnumerate(function ($collection) {
+            $collection->throttle(10);
+        });
+
+        $this->assertEnumerates(5, function ($collection) {
+            $collection->throttle(10)->take(5)->all();
+        });
+
+        $this->assertEnumeratesOnce(function ($collection) {
+            $collection->throttle(10)->all();
+        });
+
+        Sleep::fake(false);
+    }
+
     public function testTimesIsLazy()
     {
         $data = LazyCollection::times(INF);

tests/Support/SupportLazyCollectionTest.php

@@ -2,9 +2,12 @@
 
 namespace Illuminate\Tests\Support;
 
+use Carbon\CarbonInterval as Duration;
+use Illuminate\Foundation\Testing\Wormhole;
 use Illuminate\Support\Carbon;
 use Illuminate\Support\Collection;
 use Illuminate\Support\LazyCollection;
+use Illuminate\Support\Sleep;
 use InvalidArgumentException;
 use Mockery as m;
 use PHPUnit\Framework\TestCase;
@@ -223,6 +226,58 @@ public function testTapEach()
         $this->assertSame([1, 2, 3, 4, 5], $tapped);
     }
 
+    public function testThrottle()
+    {
+        Sleep::fake();
+
+        $data = LazyCollection::times(3)
+            ->throttle(2)
+            ->all();
+
+        Sleep::assertSlept(function (Duration $duration) {
+            $this->assertEqualsWithDelta(
+                2_000_000, $duration->totalMicroseconds, 1_000
+            );
+
+            return true;
+        }, times: 3);
+
+        $this->assertSame([1, 2, 3], $data);
+
+        Sleep::fake(false);
+    }
+
+    public function testThrottleAccountsForTimePassed()
+    {
+        Sleep::fake();
+        Carbon::setTestNow(now());
+
+        $data = LazyCollection::times(3)
+            ->throttle(3)
+            ->tapEach(function ($value, $index) {
+                if ($index == 1) {
+                    // Travel in time...
+                    (new Wormhole(1))->second();
+                }
+            })
+            ->all();
+
+        Sleep::assertSlept(function (Duration $duration, int $index) {
+            $expectation = $index == 1 ? 2_000_000 : 3_000_000;
+
+            $this->assertEqualsWithDelta(
+                $expectation, $duration->totalMicroseconds, 1_000
+            );
+
+            return true;
+        }, times: 3);
+
+        $this->assertSame([1, 2, 3], $data);
+
+        Sleep::fake(false);
+        Carbon::setTestNow();
+    }
+
     public function testUniqueDoubleEnumeration()
     {
         $data = LazyCollection::times(2)->unique();