How do I employ cache busting in a template?

[ugyballoons]

Hi,
I'm enjoying working with aiohttp and jinja2.
It's not clear to me how to employ cache busting. Please could someone help?
In the setup I have:

sub_app.add_routes(
    [
        web.static(
            "/static",
            Path(__file__).parent / "static",
            name="static",
            append_version=True,
        ),
    ]
)
sub_app["static_root_url"] = "/path-to/static"
env = aiohttp_jinja2.get_env(sub_app)
env.globals.update(
    zip=zip,
    url_for=web.Resource.url_for
)

and in the template I have:
<link rel="stylesheet" href="{{ url_for('static', filename='stylesheets/main.css') }}">

I feel that I shouldn't be passing url_for in the globals but if I don't, then jinja complains that there's no such function. Where am I going wrong?

[Dreamsorcerer]

I think your question is in the wrong repo, but if you can't access url_for(), then you've probably missed the setup() call, as shown in the usage:
https://aiohttp-jinja2.readthedocs.io/en/stable/#usage

I think each sub app will need to be setup separately from the root app (maybe that should be mentioned in the docs).

[Dreamsorcerer]

Well, the append_version is on the route, so it seems like something that should work. Feel free to look into the code and try to come up with a solution.

static() is at: https://github.com/aio-libs/aiohttp-jinja2/blob/master/aiohttp_jinja2/helpers.py#L61
It seems to currently just get app["static_root_url"], which is just manually entered by the user. This has always seemed slightly awkward to me, but I guess the main purpose is to point to another location for static sources (e.g. a CDN or node dev server). Maybe we need to add append_version logic into this function...

I think to use the existing append_version feature, you would need to use .url_for() on the static router.
Your previous code just assigns url_for to a random unbound method, which can't be right. The normal way in aiohttp, is using the method on the router, accessed through your app: https://docs.aiohttp.org/en/stable/web_quickstart.html#reverse-url-constructing-using-named-resources

[ugyballoons]

That last link pointed me to the solution, thank you!

I hadn't put twos together but it's there in the signature for

aiohttp.web.static(prefix, path, *, name=None, expect_handler=None, chunk_size=256 * 1024, show_index=False, follow_symlinks=False, append_version=False)

That is a named resource it's setting as a route, so all I need to do in the template is

 <link rel="stylesheet" href="{{ url('static', filename='stylesheets/main.css') }}">

and it works.

As regards to the warnings that are in the aiohttp docs for only using the app to serve files in development, I may have got the wrong end of the stick but isn't cache busting by appending a hash query to URLs effective, however those files are being served? I mean, if a reverse proxy is being used, isn't that the same difference to a browser, where the request to ignore the cache is actually being done?

[Dreamsorcerer]

and it works.

Great, maybe we can add something to the docs about this. Although it is unclear to me how this should work in relation to static() currently.

As regards to the warnings that are in the aiohttp docs for only using the app to serve files in development, I may have got the wrong end of the stick but isn't cache busting by appending a hash query to URLs effective, however those files are being served?

You'd have to point me to which part you are reading. Static files should only be getting served from the app during development, but if you have nginx or something to serve the files, then the app is not serving them, even if you leave the code in so it is capable of it. It just avoids running expensive Python processes to serve a simple file.

[ugyballoons]

Great, maybe we can add something to the docs about this. Although it is unclear to me how this should work in relation to static() currently.

Yes, it would be useful, I think, to demonstrate how url() hooks up with static routing. The named filename attribute isn't mentioned at all. Is this something I could help with?

Static files should only be getting served from the app during development, but if you have nginx or something to serve the files, then the app is not serving them, even if you leave the code in so it is capable of it. It just avoids running expensive Python processes to serve a simple file.

Good to know!

[Dreamsorcerer]

Yes, it would be useful, I think, to demonstrate how url() hooks up with static routing. The named filename attribute isn't mentioned at all. Is this something I could help with?

Feel free to make a PR if you have a suggestion. Otherwise, I'll try and take a look some time later.