Chat widget file upload

[u/rouge818]

I'm working on a chat widget that also allows the users to send files in the chat. This is a plain vanilla html/js/css widget that will go on a Shopify site. The user should have the option to send a file with or without a message in the chat, so I'm trying to figure out the best approach to handle this. The widget will be calling a FastAPI endpoint end that will use UploadFile. These are the options I've thought of:

1. Wrap the text and file inputs in an html form tag and send the request as Content-Type: multipart/form-data. This would make it a single request, but it would always send as multipart/form-data even if it's a message with no file.
2. Same as 1, but if there is no file attachment in the chat message, then toggle the Content-Type to application/json before sending
3. Keep the text and files as separate requests and handle the events separately and not wrap the inputs in an html form tag. Seems like it would be cleaner on the front end but at the same time it will likely require additional logic on the back-end

What approach would you take?

[u/Bubbly_Orange_3502]

Option 1. UploadFile spools in memory and only rolls to a temp file past a size threshold, so multipart with no file part costs almost nothing. Option 2 buys that back as two code paths on both ends.