[11.x] Collection average/avg optimization (#51512)

* optimize avg

* styleci

* formatting

---------

Co-authored-by: Taylor Otwell <taylor@laravel.com>

Author: bert-w

src/Illuminate/Collections/Collection.php

@@ -75,25 +75,6 @@ public function lazy()
         return new LazyCollection($this->items);
     }
 
-    /**
-     * Get the average value of a given key.
-     *
-     * @param  (callable(TValue): float|int)|string|null  $callback
-     * @return float|int|null
-     */
-    public function avg($callback = null)
-    {
-        $callback = $this->valueRetriever($callback);
-
-        $items = $this
-            ->map(fn ($value) => $callback($value))
-            ->filter(fn ($value) => ! is_null($value));
-
-        if ($count = $items->count()) {
-            return $items->sum() / $count;
-        }
-    }
-
     /**
      * Get the median of a given key.
      *

src/Illuminate/Collections/LazyCollection.php

@@ -154,17 +154,6 @@ public function remember()
         });
     }
 
-    /**
-     * Get the average value of a given key.
-     *
-     * @param  (callable(TValue): float|int)|string|null  $callback
-     * @return float|int|null
-     */
-    public function avg($callback = null)
-    {
-        return $this->collect()->avg($callback);
-    }
-
     /**
      * Get the median of a given key.
      *

src/Illuminate/Collections/Traits/EnumeratesValues.php

@@ -175,6 +175,28 @@ public static function times($number, ?callable $callback = null)
             ->map($callback);
     }
 
+    /**
+     * Get the average value of a given key.
+     *
+     * @param  (callable(TValue): float|int)|string|null  $callback
+     * @return float|int|null
+     */
+    public function avg($callback = null)
+    {
+        $callback = $this->valueRetriever($callback);
+
+        $reduced = $this->reduce(static function (&$reduce, $value) use ($callback) {
+            if (! is_null($resolved = $callback($value))) {
+                $reduce[0] += $resolved;
+                $reduce[1]++;
+            }
+
+            return $reduce;
+        }, [0, 0]);
+
+        return $reduced[1] ? $reduced[0] / $reduced[1] : null;
+    }
+
     /**
      * Alias for the "avg" method.
      *

tests/Support/SupportCollectionTest.php

@@ -4076,6 +4076,9 @@ public function testGettingAvgItemsFromCollection($collection)
             (object) ['foo' => 6],
         ]);
         $this->assertEquals(3, $c->avg('foo'));
+
+        $c = new $collection([0]);
+        $this->assertEquals(0, $c->avg());
     }
 
     #[DataProvider('collectionClassProvider')]