Fix query builder delete (#1130)

* fix query builder delete

* tweak a bit

* tweak the test

src/Jenssegers/Mongodb/Query/Builder.php

@@ -611,6 +611,13 @@ class Builder extends BaseBuilder
      */
     public function delete($id = null)
     {
+        // If an ID is passed to the method, we will set the where clause to check
+        // the ID to allow developers to simply and quickly remove a single row
+        // from their database without manually specifying the where clauses.
+        if (! is_null($id)) {
+            $this->where('_id', '=', $id);
+        }
+
         $wheres = $this->compileWheres();
         $result = $this->collection->DeleteMany($wheres);
         if (1 == (int) $result->isAcknowledged()) {

tests/QueryBuilderTest.php

@@ -11,6 +11,40 @@ class QueryBuilderTest extends TestCase
         DB::collection('items')->truncate();
     }
 
+    public function testDeleteWithId()
+    {
+        $user = DB::collection('users')->insertGetId([
+            ['name' => 'Jane Doe', 'age' => 20],
+        ]);
+
+        $user_id = (string) $user;
+
+        DB::collection('items')->insert([
+            ['name' => 'one thing', 'user_id' => $user_id],
+            ['name' => 'last thing', 'user_id' => $user_id],
+            ['name' => 'another thing', 'user_id' => $user_id],
+            ['name' => 'one more thing', 'user_id' => $user_id],
+        ]);
+
+        $product = DB::collection('items')->first();
+
+        $pid = (string) ($product['_id']);
+
+        DB::collection('items')->where('user_id', $user_id)->delete($pid);
+
+        $this->assertEquals(3, DB::collection('items')->count());
+
+        $product = DB::collection('items')->first();
+
+        $pid = $product['_id'];
+
+        DB::collection('items')->where('user_id', $user_id)->delete($pid);
+
+        DB::collection('items')->where('user_id', $user_id)->delete(str_random(32));
+
+        $this->assertEquals(2, DB::collection('items')->count());
+    }
+
     public function testCollection()
     {
         $this->assertInstanceOf('Jenssegers\Mongodb\Query\Builder', DB::collection('users'));