Allow dynamic intervals in DATE_ADD & DATE_SUB for SQLite

lib/Doctrine/DBAL/Platforms/SqlitePlatform.php

@@ -150,6 +150,10 @@ class SqlitePlatform extends AbstractPlatform
                         break;
                 }
 
+                if (!is_numeric($interval)) {
+                    $interval = "' || " . $interval . " || '";
+                }
+
                 return "DATE(" . $date . ",'" . $operator . $interval . " " . $unit . "')";
         }
     }

tests/Doctrine/Tests/DBAL/Platforms/SqlitePlatformTest.php

@@ -749,4 +749,14 @@ class SqlitePlatformTest extends AbstractPlatformTestCase
     {
         self::assertContains("'Foo''Bar\\'", $this->_platform->getListTableForeignKeysSQL("Foo'Bar\\"), '', true);
     }
+
+    public function testDateAddStaticNumberOfDays()
+    {
+        self::assertSame("DATE(rentalBeginsOn,'+12 DAY')", $this->_platform->getDateAddDaysExpression('rentalBeginsOn', 12));
+    }
+
+    public function testDateAddNumberOfDaysFromColumn()
+    {
+        self::assertSame("DATE(rentalBeginsOn,'+' || duration || ' DAY')", $this->_platform->getDateAddDaysExpression('rentalBeginsOn', 'duration'));
+    }
 }