Nginx - WSGI - Flask - File upload is failing - file

Question

I'm trying to upload files from my web app to my flask server that serves as API for the app.
As mentioned in the title I'm using Nginx as my webserver and running the flask app using WSGI.
This is the code in the webapp (React):
const formData = new FormData()
files.forEach((file) => {
formData.append("files", file)
})
console.log('files', files)
console.log('formData', formData)
axios.post('https://api.web.app/uploadfile', formData, {
headers: {
'Content-Type': 'multipart/form-data'
}
}).then(response => {
console.log('response.data.imgUrls', response.data.imgUrls)
if (DLOrSOW === 'sow') {
setSOWImgUrls(response.data.imgUrls)
} else {
setDLImgUrls(response.data.imgUrls)
}
})
}
This is the code on Flask:
#app.route('/uploadfile', methods=['POST'])
# #token_required
def upload_file():
print("Req is POST")
# check if the post request has the file part
if 'files' not in request.files:
print("No file found")
flash('No file')
return redirect(request.url)
files = request.files.getlist('files')
print(" files ", files)
filePaths = []
for file in files:
if file.filename == '':
flash('No selected file')
return redirect(request.url)
if file and allowed_file(file.filename):
filename = secure_filename(file.filename)
file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
print("url_for('download_file', name=filename)", url_for('download_file', name=filename))
filePaths.append(url_for('download_file', name=filename))
return jsonify({'imgUrls':filePaths })
Client(browser) respond in Console:
Request header field Authorization is not allowed by Access-Control-Allow-Headers.
[Error] XMLHttpRequest cannot load https://api.web.app/uploadfile due to access control checks.
On the other side in Flask logs I can see this request:
Oct 20 18:31:49 API uwsgi[1709272]: [pid: 1709272|app: 0|req: 36/81] 111.11.11.1 () {50 vars in 805 bytes} [Wed Oct 20 18:31:49 2021] OPTIONS /uploadfile => generated 6 bytes in 6 msecs (HTTP/1.1 200) 3 headers in 110 bytes (1 switches on core 0)
Just want to add that everything else works as it should. I'm able to do post, get, put etc requests to every other path in the Flask.
I think that the part that causes this is the use of "new FormData()"

Answer 1

In this case, for my situation, the problem was fixed by adding 'GET' parameter in the Flask path:
#app.route('/uploadfile', methods=['GET, 'POST'])
Apparently the order of the methods is important too