fix: carry the sign on the interval instead of on each unit

src/Duration.php

@@ -188,14 +188,13 @@ final class Duration
     {
         $units += ['hour' => '0', 'minute' => '0', 'second' => '0', 'fraction' => '0', 'sign' => '+'];
         $units['fraction'] = str_pad($units['fraction'] ?? '000000', 6, '0');
-        $sign = '-' === $units['sign'] ? '-' : '';
 
-        return self::fromDateString(
-            $sign.$units['hour'].' hours '
-            .$sign.$units['minute'].' minutes '
-            .$sign.$units['second'].' seconds '
-            .$sign.$units['fraction'].' microseconds'
-        );
+        $instance = self::fromDateString($units['hour'].' hours '.$units['minute'].' minutes '.$units['second'].' seconds '.$units['fraction'].' microseconds');
+        if ('-' === $units['sign']) {
+            $instance->dateInterval->invert = 1;
+        }
+
+        return $instance;
     }
 
     /**

src/DurationTest.php

@@ -24,6 +24,7 @@ namespace League\Period;
 
 use DateInterval;
 use DateTime;
+use DateTimeImmutable;
 use DateTimeInterface;
 use DateTimeZone;
 use InvalidArgumentException;
@@ -49,7 +50,8 @@ final class DurationTest extends TestCase
     {
         $interval = $duration->dateInterval;
 
-        $date = ['P'];
+        // the sign belongs to the whole duration: -PT12M28S, not PT-12M-28S
+        $date = [1 === $interval->invert ? '-P' : 'P'];
         if (0 !== $interval->y) {
             $date[] = '%yY';
         }
@@ -242,7 +244,7 @@ final class DurationTest extends TestCase
             ],
             'negative chrono' => [
                 'chronometer' => '-12:28',
-                'expected' => 'PT-12M-28S',
+                'expected' => '-PT12M28S',
             ],
         ];
     }
@@ -282,11 +284,11 @@ final class DurationTest extends TestCase
             ],
             'negative chrono' => [
                 'chronometer' => '-12:28',
-                'expected' => 'PT-12H-28M',
+                'expected' => '-PT12H28M',
             ],
             'negative chrono with seconds' => [
                 'chronometer' => '-01:02:28',
-                'expected' => 'PT-1H-2M-28S',
+                'expected' => '-PT1H2M28S',
             ],
         ];
     }
@@ -295,11 +297,17 @@ final class DurationTest extends TestCase
      * A sign applies to the whole duration, not just the hour. It used to be
      * lost when the hour was zero, and to negate only the hour otherwise.
      */
+    /**
+     * @param 'fromChronoString'|'fromTimeString' $method
+     */
     #[DataProvider('signedDurationProvider')]
     public function testSignedStringsApplySignToWholeDuration(string $method, string $input, string $reference, string $expected): void
     {
-        $duration = Duration::$method($input);
-        $date = new \DateTimeImmutable($reference);
+        $duration = match ($method) {
+            'fromChronoString' => Duration::fromChronoString($input),
+            'fromTimeString' => Duration::fromTimeString($input),
+        };
+        $date = new DateTimeImmutable($reference);
 
         self::assertSame(
             $expected,
@@ -308,7 +316,7 @@ final class DurationTest extends TestCase
     }
 
     /**
-     * @return iterable<string, array{method:string, input:string, reference:string, expected:string}>
+     * @return iterable<string, array{method:'fromChronoString'|'fromTimeString', input:string, reference:string, expected:string}>
      */
     public static function signedDurationProvider(): iterable
     {