feat: FilePicker.upload() supports modifying filenames before upload

[ndonkoHenri]

Resolves #5037

Test Code

import random

import flet as ft


def main(page: ft.Page):
    def pick_files_result(e: ft.FilePickerResultEvent):
        selected_files.value = (
            ", ".join(map(lambda f: f.name, e.files)) if e.files else "Cancelled!"
        )
        selected_files.update()

    def upload_files(e):
        upload_list = []
        if fp.result is not None and fp.result.files is not None:
            for f in fp.result.files:
                new_name = f"{random.randint(1, 1000)}_{f.name}"
                upload_list.append(
                    ft.FilePickerUploadFile(
                        name=new_name,
                        upload_url=page.get_upload_url(new_name, 600),
                        id=f.id,
                    )
                )
            fp.upload(upload_list)

    fp = ft.FilePicker(on_result=pick_files_result)
    page.overlay.append(fp)

    page.add(
        ft.Row(
            [
                ft.ElevatedButton("Upload", on_click=upload_files),
                ft.ElevatedButton(
                    "Pick files",
                    icon=ft.Icons.UPLOAD_FILE,
                    on_click=lambda _: fp.pick_files(allow_multiple=True),
                ),
                selected_files := ft.Text(),
            ]
        )
    )


ft.app(main, upload_dir="uploads")

Summary by Sourcery

New Features:

• The FilePicker.upload() method now supports specifying a new name for each file in the upload list, allowing modification of filenames before upload.