Form submit without action/redirect/display

I have a form embedded in my custom sidebar and I want the user to stay on the same page after the validation. The problem is that the validation cause the form to display itself replacing the whole page.

Here is the markdown '_pages/modules/subscribe/form.fr.md_'
```html
---
title: My contact Form
process:
markdown: true
twig: true
form:
name: contact-form
fields:
- name: email
label: Recevoir toutes les nouveautés directement
autocomplete: on
placeholder: Votre e-mail
type: email

buttons:
- type: submit
value: Valider

process:
- save:
filename: newsLetterFR.csv
extension: csv
body: "{{ form.value.email|e }}\n"
operation: add
---
```
Maybe the problem is how I integrated the form in '_myThemeDerivatedFromQuark/templates/partials/sidebar.html.twig_

```html

I tried action: "." , action: "" , action: . , action: without success.

I think the problem comes from 'plugins/form/templates/forms/default/form.html.twig' line 20
'{% set action = form.action ?: page.route ~ uri.params %}'

"form.action" is defaulted to "modules/subscribe" by the calling code. I tried to backtrace the problem but failed miserably...