Symfony version(s) affected

5.4, 6.2

Description

#38323 introduced the possibility to have multiple parts with the same name. However, this PR added some issues: A from element, such as <input type="hidden" name="bar[0][foo]"> is resolved as bar[foo]. But that is wrong, bar[0][foo] is correct. Also it introduced a limitation in the sense if the field name is actually meant to be an integer, eg the following currently is throwing an exception:

new FormDataPart([
    '1' => [
        'a' => 'one',
        'b' => 'two',
    ],
]);

How to reproduce

Create a form containing

```html
<input type="hidden" name="bar[0][foo]" value="v1">

will resolve as bar[foo].

Then create improve the form as...

<input type="hidden" name="bar[0][foo]" value="v1">
<input type="hidden" name="bar[0][baz]" value="v2">

will throw an exception.

Use the HttpBrowser to post the forms.

Possible Solution

• Fix to the the field naming bug.
• Remove the limitation
• Keep the current feature introduced in [Mime] Allow multiple parts with the same name in FormDataPart #38323