With App Engine Python27(standard env), it was possible to create a webapp that only serves static resources from the app.yaml. Without writing any Python script.
With Python37 (standard env), I see that it's still possible to have the static_dir in the handlers section of app.yaml but I'm wondering if this will work the same way. Cause I don't define any entrypoint, I don't set a webserver. I have only the app.yaml at the moment.
And the first that blocks me at the moment: if doing so, how do I locally run this app ? (no Python script so no python main.py and dev_appserver.py does not work for Python37).
Thanks for your answers
Yes, the static_dir and static_file configurations work the same way, their sections in the app.yaml reference docs for 2.7 and 3.7 are identical except for the references to the 2.7-specific application_readable option.
Since serving the static content on GAE is identical (the static content is uploaded and served separately from the application code - equivalent, if you want, to serving from a CDN) it doesn't really matter if you're using the 2.7 runtime or the 3.7 one - you're not actually executing any python code, right?
So one option would be to just use 2.7 instead (adding a minimal app skeleton to keep the runtime happy, say by just returning 404 or redirecting to one of the static pages - you can get it from the Quickstart). You can then continue to use the 2.7 development server for local execution.
Another option would be to use 2.7 (as in option 1) just for local development, but switch back to 3.7 for deployment (i.e. update the app.yaml file, drop the skeleton app code or update it for 3.7). A bit more tedious and brittle, but it can be done.
A 3rd option would be to try the updated development server which has some limited support for 3.7, see Python 3.7 Local Development Server Options for new app engine apps. Serving static content might be included in that limited support. You'd need to meet its specific requirements. You'd also need a 3.7-compatible skeleton app, you can get one from the 3.7 Quickstart.
Finally, you could also use some other tool locally during development, if you have one (same advice as for running an actual app locally). It could simply be your browser for static-only content :) Again, the goal is to just develop your static content, GAE will serve it the same way. You won't need any skeleton app in this case.
Side note: I saw this in the Node.js standard env app.yaml reference, not sure if it's applicable to python 3.7 as well, just be aware of it:
In order to use static handlers, at least one of your handlers must contain the line script: auto to deploy successfully.