Fix LazyCollection#unique() double enumeration

Fixes #38817

src/Illuminate/Collections/Collection.php

@@ -1411,6 +1411,28 @@ public function transform(callable $callback)
         return $this;
     }
 
+    /**
+     * Return only unique items from the collection array.
+     *
+     * @param  string|callable|null  $key
+     * @param  bool  $strict
+     * @return static
+     */
+    public function unique($key = null, $strict = false)
+    {
+        $callback = $this->valueRetriever($key);
+
+        $exists = [];
+
+        return $this->reject(function ($item, $key) use ($callback, $strict, &$exists) {
+            if (in_array($id = $callback($item, $key), $exists, $strict)) {
+                return true;
+            }
+
+            $exists[] = $id;
+        });
+    }
+
     /**
      * Reset the keys on the underlying array.
      *

src/Illuminate/Collections/LazyCollection.php

@@ -1352,6 +1352,30 @@ public function tapEach(callable $callback)
         });
     }
 
+    /**
+     * Return only unique items from the collection array.
+     *
+     * @param  string|callable|null  $key
+     * @param  bool  $strict
+     * @return static
+     */
+    public function unique($key = null, $strict = false)
+    {
+        $callback = $this->valueRetriever($key);
+
+        return new static(function () use ($callback, $strict) {
+            $exists = [];
+
+            foreach ($this as $key => $item) {
+                if (! in_array($id = $callback($item, $key), $exists, $strict)) {
+                    yield $key => $item;
+
+                    $exists[] = $id;
+                }
+            }
+        });
+    }
+
     /**
      * Reset the keys on the underlying array.
      *

src/Illuminate/Collections/Traits/EnumeratesValues.php

@@ -773,28 +773,6 @@ public function reject($callback = true)
         });
     }
 
-    /**
-     * Return only unique items from the collection array.
-     *
-     * @param  string|callable|null  $key
-     * @param  bool  $strict
-     * @return static
-     */
-    public function unique($key = null, $strict = false)
-    {
-        $callback = $this->valueRetriever($key);
-
-        $exists = [];
-
-        return $this->reject(function ($item, $key) use ($callback, $strict, &$exists) {
-            if (in_array($id = $callback($item, $key), $exists, $strict)) {
-                return true;
-            }
-
-            $exists[] = $id;
-        });
-    }
-
     /**
      * Return only unique items from the collection array using strict comparison.
      *

tests/Support/SupportLazyCollectionTest.php

@@ -203,4 +203,13 @@ public function testTapEach()
         $this->assertSame([1, 2, 3, 4, 5], $data);
         $this->assertSame([1, 2, 3, 4, 5], $tapped);
     }
+
+    public function testUniqueDoubleEnumeration()
+    {
+        $data = LazyCollection::times(2)->unique();
+
+        $data->all();
+
+        $this->assertSame([1, 2], $data->all());
+    }
 }