/usr/local/bin/lighttpd-starter allows overriding the php configuration, by only inserting the standard config if:
if [ ! -r $home/.lighttpd.conf ] || [[ ! $(cat "$home/.lighttpd.conf" | grep -P '^(?:[ \t]*fastcgi.server[ \t\+\(=]+".php"|#no-default-php)') ]]; then
This should be documented.
Probably just need to document the lighttpd-plain backend better on https://wikitech.wikimedia.org/wiki/Help:Tool_Labs/Web/Lighttpd
Reading this task again I realized that the feature that it is asking to be documented actually is no longer available. lighttpd-starter was replaced in the "webservice2" re-write and equivalent functionality was not added in the new implementation. Specifically there is no magic string of config that can be placed in a tool's $HOME/.lighttpd.conf file that will prevent the default server configuration from being used. There is also no Kubernetes backend equivalent for the gridengine backend's "lighttpd-plain" type today.
So... ugh. We probably need some product work before we are actually ready to document this "feature".
Guess once this is possible it could go to https://wikitech.wikimedia.org/wiki/Help:Toolforge/Web/Lighttpd#PHP ?
lighttpd-starter was replaced in the "webservice2" re-write and equivalent functionality was not added in the new implementation.
For reference: T98440: Deploy new unified webservice code / T98441: Convert lighttpd-starter from bash to python
So... ugh. We probably need some product work before we are actually ready to document this "feature".
As this is a documentation task, there should be a subtask which is about developing / re-adding this functionality.
Let's just close this as declined since the missing docs are actually a missing feature that the world has lived without for 4+ years.