Introduce Result::all()

src/Result.php

@@ -95,4 +95,25 @@ public static function extractErrors(array $results): array
             [],
         );
     }
+
+    /**
+     * If all given results are Success,
+     *  returns a Success with array of extracted Success values.
+     * Otherwise, if at least one is an Error
+     *  returns an Error with array of extracted Error values.
+     *
+     * @psalm-pure
+     * @template T
+     * @template E
+     * @param list<ResultInterface<T, E>> $results
+     * @return ResultInterface<list<T>, list<E>>
+     */
+    public static function all(array $results): ResultInterface
+    {
+        $errors = self::extractErrors($results);
+
+        return empty($errors)
+            ? self::success(self::extractSuccesses($results))
+            : self::error($errors);
+    }
 }

test/ResultTest.php

@@ -194,4 +194,35 @@ public function testEnsureErrorDoesNotChangePreviousError(): void
         $ensured = $result->ensure(fn(int $i) => $i > 100, 'new error');
         self::assertEquals('old error', $ensured->get());
     }
+
+    public function testAllWhenOnlySuccesses(): void
+    {
+        $resultA = Result::success('A');
+        $resultB = Result::success(23);
+
+        $all = Result::all([ $resultA, $resultB ]);
+        self::assertInstanceOf(Success::class, $all);
+        self::assertEquals([ 'A', 23 ], $all->get());
+    }
+
+    public function testAllWhenOnlyErrors(): void
+    {
+        $resultA = Result::error(1);
+        $resultB = Result::error('B');
+
+        $all = Result::all([ $resultA, $resultB ]);
+        self::assertInstanceOf(Error::class, $all);
+        self::assertEquals([ 1, 'B' ], $all->get());
+    }
+
+    public function testAllWhenMixedErrorsAndSuccesses(): void
+    {
+        $resultA = Result::error(1);
+        $resultB = Result::success('B');
+        $resultC = Result::error(false);
+
+        $all = Result::all([ $resultA, $resultB, $resultC ]);
+        self::assertInstanceOf(Error::class, $all);
+        self::assertEquals([ 1, false ], $all->get());
+    }
 }