add download event

[Lendemor]

All Submissions:

• Have you followed the guidelines stated in CONTRIBUTING.md file?
• Have you checked to ensure there aren't any other open Pull Requests for the desired changed?

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

New Feature Submission:

• Does your submission pass the tests?
• Have you linted your code locally prior to submission?

Description

Add an API for easily downloading files.

Usage is as follow:

rx.button("Download file", on_click=rx.download("/uri/for/file.extension", "target_file.extension")

or

def export_data(self):
    ...
    # do export logic here and write to filepath
    # then
    yield rx.download(filepath, filename)

[masenf]

I'm a little unclear on why this would be preferred over just using a standard link. This seems like more moving parts and harder to deal with error handling.

If I wanted to provide a download link, I would keep the href in a state Var and render a normal <a> tag in the frontend.

[Lendemor]

I'm a little unclear on why this would be preferred over just using a standard link. This seems like more moving parts and harder to deal with error handling.

If I wanted to provide a download link, I would keep the href in a state Var and render a normal <a> tag in the frontend.

This only work if the file is already available beforehand.
Using a <a> with a href doesn't let you execute an event handler before starting the download.

Take an example where you have a data_table and an export button.
You can see your data in the datatable, but the file doesn't exist yet (you could want to apply some filter before export etc..)
Clicking an export button will trigger an event handler where you can both do your logic and then yield the front side download event.

[masenf]

Using a <a> with a href doesn't let you execute an event handler before starting the download.

Fair enough, but is it possible make the hidden <a> that gets clicked link to the actual URL and let the client browser deal with the error handling? Or is there some security restriction that requires the clicked link href to be a URL.createObjectURL?

[picklelo]

Code works well for me! Just one suggestion

[picklelo]

If they don't provide a filename, maybe we can default to the last part of the path in the url? Basically give it the same filename it was saved as

[Lendemor]

Sure we could do that

[picklelo]

awesome, great work

[picklelo]

nit: Instead of Optional we can do str | None now

[masenf]

Sorry didn't re-review, but the merged implementation is killer, thanks for making the changes @Lendemor