so with --spa.serve-existing enabled, ws will do file system I/O for every incoming HTTP request, regardless what it's for. So you'll be doing constant filesystem I/O for existance of files with names like /one/two/53%C2%B031'22.0%22N+2%C2%B013'21.0%22W/@53.5227778,-2.2246887,17z/data=!3m1!4b1!4m5!3m4!1s0x0:0x0!8m2!3d53.5227778!4d-2.2225 etc.

I'm not yet convinced this is 100% efficient and should baked into ws..

It's the same as the -f in Apache RewriteCond: https://httpd.apache.org/docs/2.4/mod/mod_rewrite.html
It's not really efficient, but it's the only way to serve SPA apps that don't have an explicit /api/ endpoint for apis. Maybe we can add it to the documentation that it's not efficient because it does filesystem I/O for every request and should only be used while developing?

Released in lws-spa v1.0.0. The option is now called --spa.asset-test-fs to indicate it's part of the same option family as --spa.asset-test.

It's not yet included in the default ws middleware stack but you can test it locally with commands like this:

npm i -D local-web-server lws-spa

# prints help for a custom stack using just the local lws-spa installation and lws-static.
# You should see the docs for `--spa.asset-test-fs`.
npx ws --stack ./node_modules/lws-spa lws-static --help 

# runs the custom stack - use this command to test the new feature
npx ws --stack ./node_modules/lws-spa lws-static --spa.asset-test-fs --spa your-spa-here.html

Let me know if you have any issues.