[10.x] Add percentage method to Collections (#48034)

* Create percentage Collection method

* Update percentage to return null for empty collections and add more test cases

* formatting

---------

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

src/Illuminate/Collections/Traits/EnumeratesValues.php

@@ -481,6 +481,25 @@ public function partition($key, $operator = null, $value = null)
         return new static([new static($passed), new static($failed)]);
     }
 
+    /**
+     * Calculate the percentage of items that pass a given truth test.
+     *
+     * @param  (callable(TValue, TKey): bool)  $callback
+     * @param  int  $precision
+     * @return float|null
+     */
+    public function percentage(callable $callback, int $precision = 2)
+    {
+        if ($this->isEmpty()) {
+            return null;
+        }
+
+        return round(
+            $this->filter($callback)->count() / $this->count() * 100,
+            $precision
+        );
+    }
+
     /**
      * Get the sum of the given values.
      *

tests/Support/SupportCollectionTest.php

@@ -5634,6 +5634,47 @@ public function testEnsureForInheritance($collection)
         $data->ensure(\Throwable::class);
     }
 
+    /**
+     * @dataProvider collectionClassProvider
+     */
+    public function testPercentageWithFlatCollection($collection)
+    {
+        $collection = new $collection([1, 1, 2, 2, 2, 3]);
+
+        $this->assertSame(33.33, $collection->percentage(fn ($value) => $value === 1));
+        $this->assertSame(50.00, $collection->percentage(fn ($value) => $value === 2));
+        $this->assertSame(16.67, $collection->percentage(fn ($value) => $value === 3));
+        $this->assertSame(0.0, $collection->percentage(fn ($value) => $value === 5));
+    }
+
+    /**
+     * @dataProvider collectionClassProvider
+     */
+    public function testPercentageWithNestedCollection($collection)
+    {
+        $collection = new $collection([
+            ['name' => 'Taylor', 'foo' => 'foo'],
+            ['name' => 'Nuno', 'foo' => 'bar'],
+            ['name' => 'Dries', 'foo' => 'bar'],
+            ['name' => 'Jess', 'foo' => 'baz'],
+        ]);
+
+        $this->assertSame(25.00, $collection->percentage(fn ($value) => $value['foo'] === 'foo'));
+        $this->assertSame(50.00, $collection->percentage(fn ($value) => $value['foo'] === 'bar'));
+        $this->assertSame(25.00, $collection->percentage(fn ($value) => $value['foo'] === 'baz'));
+        $this->assertSame(0.0, $collection->percentage(fn ($value) => $value['foo'] === 'test'));
+    }
+
+    /**
+     * @dataProvider collectionClassProvider
+     */
+    public function testPercentageReturnsNullForEmptyCollections($collection)
+    {
+        $collection = new $collection([]);
+
+        $this->assertNull($collection->percentage(fn ($value) => $value === 1));
+    }
+
     /**
      * Provides each collection class, respectively.
      *