Fixed inconsistency in handling date differences between platforms

The SQLite and Oracle platforms produces a `ROUND()`'ed or `TRUNC()`'ated difference between the datetimes. However it should be the difference between dates.

lib/Doctrine/DBAL/Platforms/OraclePlatform.php

@@ -160,14 +160,10 @@ class OraclePlatform extends AbstractPlatform
 
     /**
      * {@inheritDoc}
-     *
-     * Note: Since Oracle timestamp differences are calculated down to the microsecond we have to truncate
-     * them to the difference in days. This is obviously a restriction of the original functionality, but we
-     * need to make this a portable function.
      */
     public function getDateDiffExpression($date1, $date2)
     {
-        return "TRUNC(TO_NUMBER(SUBSTR((" . $date1 . "-" . $date2 . "), 1, INSTR(" . $date1 . "-" . $date2 .", ' '))))";
+        return sprintf('TRUNC(%s) - TRUNC(%s)', $date1, $date2);
     }
 
     /**

lib/Doctrine/DBAL/Platforms/SqlitePlatform.php

@@ -174,7 +174,7 @@ class SqlitePlatform extends AbstractPlatform
      */
     public function getDateDiffExpression($date1, $date2)
     {
-        return 'ROUND(JULIANDAY('.$date1 . ')-JULIANDAY('.$date2.'))';
+        return sprintf("JULIANDAY(%s, 'start of day') - JULIANDAY(%s, 'start of day')", $date1, $date2);
     }
 
     /**

tests/Doctrine/Tests/DBAL/Functional/DataAccessTest.php

@@ -5,7 +5,6 @@ namespace Doctrine\Tests\DBAL\Functional;
 use Doctrine\DBAL\Connection;
 use Doctrine\DBAL\FetchMode;
 use Doctrine\DBAL\ParameterType;
-use Doctrine\DBAL\Platforms\AbstractPlatform;
 use Doctrine\DBAL\Platforms\TrimMode;
 use Doctrine\DBAL\Types\Type;
 use const CASE_LOWER;
@@ -531,7 +530,6 @@ class DataAccessTest extends \Doctrine\Tests\DbalFunctionalTestCase
     {
         $p = $this->_conn->getDatabasePlatform();
         $sql = 'SELECT ';
-        $sql .= $p->getDateDiffExpression('test_datetime', $p->getCurrentTimestampSQL()) .' AS diff, ';
         $sql .= $p->getDateAddSecondsExpression('test_datetime', 1) .' AS add_seconds, ';
         $sql .= $p->getDateSubSecondsExpression('test_datetime', 1) .' AS sub_seconds, ';
         $sql .= $p->getDateAddMinutesExpression('test_datetime', 5) .' AS add_minutes, ';
@@ -553,8 +551,6 @@ class DataAccessTest extends \Doctrine\Tests\DbalFunctionalTestCase
         $row = $this->_conn->fetchAssoc($sql);
         $row = array_change_key_case($row, CASE_LOWER);
 
-        $diff = (strtotime('2010-01-01') - strtotime(date('Y-m-d'))) / 3600 / 24;
-        self::assertEquals($diff, $row['diff'], "Date difference should be approx. ".$diff." days.", 1);
         self::assertEquals('2010-01-01 10:10:11', date('Y-m-d H:i:s', strtotime($row['add_seconds'])), "Adding second should end up on 2010-01-01 10:10:11");
         self::assertEquals('2010-01-01 10:10:09', date('Y-m-d H:i:s', strtotime($row['sub_seconds'])), "Subtracting second should end up on 2010-01-01 10:10:09");
         self::assertEquals('2010-01-01 10:15:10', date('Y-m-d H:i:s', strtotime($row['add_minutes'])), "Adding minutes should end up on 2010-01-01 10:15:10");

tests/Doctrine/Tests/DBAL/Functional/Platform/DateExpressionTest.php

+<?php
+
+namespace Doctrine\Tests\DBAL\Functional\Platform;
+
+use DateTimeImmutable;
+use Doctrine\DBAL\Schema\Table;
+use Doctrine\Tests\DbalFunctionalTestCase;
+use function sprintf;
+
+class DateExpressionTest extends DbalFunctionalTestCase
+{
+    /**
+     * @dataProvider differenceProvider
+     */
+    public function testDifference(string $date1, string $date2, int $expected) : void
+    {
+        $table = new Table('date_expr_test');
+        $table->addColumn('date1', 'date');
+        $table->addColumn('date2', 'date');
+        $this->_conn->getSchemaManager()->dropAndCreateTable($table);
+        $this->_conn->insert('date_expr_test', [
+            'date1' => $date1,
+            'date2' => $date2,
+        ]);
+
+        $platform = $this->_conn->getDatabasePlatform();
+
+        $sql  = sprintf('SELECT %s FROM date_expr_test', $platform->getDateDiffExpression('date1', 'date2'));
+        $diff = $this->_conn->query($sql)->fetchColumn();
+
+        self::assertEquals($expected, $diff);
+    }
+
+    /**
+     * @return string[][]|int[][]
+     */
+    public static function differenceProvider() : iterable
+    {
+        $date1    = new DateTimeImmutable();
+        $date2    = new DateTimeImmutable('2018-04-10 10:10:10');
+        $expected = $date1->modify('midnight')->diff(
+            $date2->modify('midnight')
+        )->days;
+
+        return [
+            'dynamic'  => [
+                $date1->format('Y-m-d H:i:s'),
+                $date2->format('Y-m-d H:i:s'),
+                $expected,
+            ],
+            'same day' => ['2018-04-14 23:59:59', '2018-04-14 00:00:00', 0],
+            'midnight' => ['2018-04-14 00:00:00', '2018-04-13 23:59:59', 1],
+        ];
+    }
+}