Fix multipart array value parsing in HTTP client (#55732) (#56302)

* Fix multipart array value parsing in HTTP client

- Fixed parseMultipartBodyFormat to handle array values correctly
- Array values are now formatted as 'field[]' entries for multipart/form-data
- Maintains backward compatibility with existing name/contents format
- Added tests for array values and mixed file+array scenarios

Fixes #55732

* Update PendingRequest.php

---------

Co-authored-by: Taylor Otwell <[email protected]>

Author: joteejotee

src/Illuminate/Http/Client/PendingRequest.php

@@ -1021,7 +1021,21 @@ protected function parseHttpOptions(array $options)
     protected function parseMultipartBodyFormat(array $data)
     {
         return (new Collection($data))
-            ->map(fn ($value, $key) => is_array($value) ? $value : ['name' => $key, 'contents' => $value])
+            ->flatMap(function ($value, $key) {
+                if (is_array($value)) {
+                    // If the array has 'name' and 'contents' keys, it's already formatted for multipart...
+                    if (isset($value['name']) && isset($value['contents'])) {
+                        return [$value];
+                    }
+
+                    // Otherwise, treat it as multiple values for the same field name...
+                    return (new Collection($value))->map(function ($item) use ($key) {
+                        return ['name' => $key.'[]', 'contents' => $item];
+                    });
+                }
+
+                return [['name' => $key, 'contents' => $value]];
+            })
             ->values()
             ->all();
     }

tests/Http/HttpClientTest.php

@@ -786,6 +786,53 @@ public function testCanSendMultipartDataWithBothSimplifiedAndExtendedParameters(
         });
     }
 
+    public function testCanSendMultipartDataWithArrayValues()
+    {
+        $this->factory->fake();
+
+        $this->factory->asMultipart()->post('http://foo.com/multipart', [
+            'name' => 'Steve',
+            'roles' => ['Network Administrator', 'Janitor'],
+        ]);
+
+        $this->factory->assertSent(function (Request $request) {
+            return $request->url() === 'http://foo.com/multipart' &&
+                Str::startsWith($request->header('Content-Type')[0], 'multipart') &&
+                $request[0]['name'] === 'name' &&
+                $request[0]['contents'] === 'Steve' &&
+                $request[1]['name'] === 'roles[]' &&
+                $request[1]['contents'] === 'Network Administrator' &&
+                $request[2]['name'] === 'roles[]' &&
+                $request[2]['contents'] === 'Janitor';
+        });
+    }
+
+    public function testCanSendMultipartDataWithFileAndArrayValues()
+    {
+        $this->factory->fake();
+
+        $this->factory
+            ->attach('attachment', 'photo_content', 'photo.jpg', ['Content-Type' => 'image/jpeg'])
+            ->post('http://foo.com/multipart', [
+                'name' => 'Steve',
+                'roles' => ['Network Administrator', 'Janitor'],
+            ]);
+
+        $this->factory->assertSent(function (Request $request) {
+            return $request->url() === 'http://foo.com/multipart' &&
+                Str::startsWith($request->header('Content-Type')[0], 'multipart') &&
+                $request[0]['name'] === 'name' &&
+                $request[0]['contents'] === 'Steve' &&
+                $request[1]['name'] === 'roles[]' &&
+                $request[1]['contents'] === 'Network Administrator' &&
+                $request[2]['name'] === 'roles[]' &&
+                $request[2]['contents'] === 'Janitor' &&
+                $request[3]['name'] === 'attachment' &&
+                $request[3]['contents'] === 'photo_content' &&
+                $request[3]['filename'] === 'photo.jpg';
+        });
+    }
+
     public function testItCanSendToken()
     {
         $this->factory->fake();