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javascriptgoogle-chromeflask

Flask - Javascript file requires multiple page refresh to load net::ERR_INVALID_HTTP_RESPONSE 200

I have a Flask app that relies on javascript for certain functionality. The javascript file loads fine sometimes and other times I get an error in the console:

GET http://localhost:5000/static/js/sm4sb.js net::ERR_INVALID_HTTP_RESPONSE 200

When this happens the javascript is not loaded. I then have to refresh the page multiple times until the console does not show this error.

I read somewhere that putting this in my config.py file should fix it, but it doesn't

SEND_FILE_MAX_AGE_DEFAULT = 0

Elsewhere someone suggested adding this:

@app.after_request
def add_header(response):
    response.headers['Cache-Control'] = 'no-cache, no-store'

But when I do that I get an error

AttributeError
AttributeError: 'NoneType' object has no attribute 'vary'

Note that the issue is with Chrome, it works without an issue running in Firefox.

EDIT: I have found a few references that suggest this is a Flask issue and to downgrade to an earlier version. I will try that and report back.

Solution

  • After submitting a bug to the Werkzeug team they said to upgrade from version 2.1.1 to the latest 2.1.2.

    Doing this fixed the issue.

    So to clarify I now run Python 3.10.4, Flask 2.1.2 and Werkzeurg 2.1.2 and this issue no longer occurs.