Merge pull request #28181 from timacdonald/collection_duplicates

[5.8] Add duplicates method to collection

Author: taylorotwell

src/Illuminate/Support/Collection.php

@@ -407,6 +407,50 @@ public function diffKeysUsing($items, callable $callback)
         return new static(array_diff_ukey($this->items, $this->getArrayableItems($items), $callback));
     }
 
+    /**
+     * Retrieve duplicate items from the collection.
+     *
+     * @param  callable|null  $callback
+     * @param  bool  $strict
+     * @return static
+     */
+    public function duplicates($callback = null, $strict = false)
+    {
+        $items = $this->map($this->valueRetriever($callback));
+
+        $uniqueItems = $items->unique(null, $strict);
+
+        $compare = $strict ? function ($a, $b) {
+            return $a === $b;
+        }
+        : function ($a, $b) {
+            return $a == $b;
+        };
+
+        $duplicates = new static;
+
+        foreach ($items as $key => $value) {
+            if ($uniqueItems->isNotEmpty() && $compare($value, $uniqueItems->first())) {
+                $uniqueItems->shift();
+            } else {
+                $duplicates[$key] = $value;
+            }
+        }
+
+        return $duplicates;
+    }
+
+    /**
+     * Retrieve duplicate items from the collection using strict comparison.
+     *
+     * @param  callable|null  $callback
+     * @return static
+     */
+    public function duplicatesStrict($callback = null)
+    {
+        return $this->duplicates($callback, true);
+    }
+
     /**
      * Execute a callback over each item.
      *

tests/Support/SupportCollectionTest.php

@@ -745,6 +745,60 @@ public function testDiffAssocUsing()
         $this->assertEquals(['b' => 'brown', 'c' => 'blue', 'red'], $c1->diffAssocUsing($c2, 'strcasecmp')->all());
     }
 
+    public function testDuplicates()
+    {
+        $duplicates = Collection::make([1, 2, 1, 'laravel', null, 'laravel', 'php', null])->duplicates()->all();
+        $this->assertSame([2 => 1, 5 => 'laravel', 7 => null], $duplicates);
+
+        // does loose comparison
+        $duplicates = Collection::make([2, '2', [], null])->duplicates()->all();
+        $this->assertSame([1 => '2', 3 => null], $duplicates);
+
+        // works with mix of primitives
+        $duplicates = Collection::make([1, '2', ['laravel'], ['laravel'], null, '2'])->duplicates()->all();
+        $this->assertSame([3 => ['laravel'], 5 => '2'], $duplicates);
+
+        // works with mix of objects and primitives **excepts numbers**.
+        $expected = new Collection(['laravel']);
+        $duplicates = Collection::make([new Collection(['laravel']), $expected, $expected, [], '2', '2'])->duplicates()->all();
+        $this->assertSame([1 => $expected, 2 => $expected, 5 => '2'], $duplicates);
+    }
+
+    public function testDuplicatesWithKey()
+    {
+        $items = [['framework' => 'vue'], ['framework' => 'laravel'], ['framework' => 'laravel']];
+        $duplicates = Collection::make($items)->duplicates('framework')->all();
+        $this->assertSame([2 => 'laravel'], $duplicates);
+    }
+
+    public function testDuplicatesWithCallback()
+    {
+        $items = [['framework' => 'vue'], ['framework' => 'laravel'], ['framework' => 'laravel']];
+        $duplicates = Collection::make($items)->duplicates(function ($item) {
+            return $item['framework'];
+        })->all();
+        $this->assertSame([2 => 'laravel'], $duplicates);
+    }
+
+    public function testDuplicatesWithStrict()
+    {
+        $duplicates = Collection::make([1, 2, 1, 'laravel', null, 'laravel', 'php', null])->duplicatesStrict()->all();
+        $this->assertSame([2 => 1, 5 => 'laravel', 7 => null], $duplicates);
+
+        // does strict comparison
+        $duplicates = Collection::make([2, '2', [], null])->duplicatesStrict()->all();
+        $this->assertSame([], $duplicates);
+
+        // works with mix of primitives
+        $duplicates = Collection::make([1, '2', ['laravel'], ['laravel'], null, '2'])->duplicatesStrict()->all();
+        $this->assertSame([3 => ['laravel'], 5 => '2'], $duplicates);
+
+        // works with mix of primitives, objects, and numbers
+        $expected = new Collection(['laravel']);
+        $duplicates = Collection::make([new Collection(['laravel']), $expected, $expected, [], '2', '2'])->duplicatesStrict()->all();
+        $this->assertSame([2 => $expected, 5 => '2'], $duplicates);
+    }
+
     public function testEach()
     {
         $c = new Collection($original = [1, 2, 'foo' => 'bar', 'bam' => 'baz']);