QDoc can't "just do it" without overkill-configuration

Summary

QDoc is not zeroconf. It requires users to specify more stuff than they may need or want to.

Steps to reproduce

Run this from e.g. qtdeclarative repo:

$ qdoc --outputdir ../doc-qtdeclarative-quick src/quick/doc/qtquick.qdocconf

Expected output

Something readable, like you know — webpages, in the destination directory.

Actual output

/home/ratijas/projects/q/qt6/qtdeclarative/src/quick/doc/src/quick/doc/qtquick.qdocconf:1: (qdoc) error: Environment variable 'QT_INSTALL_DOCS' undefined
Environment variable 'QT_INSTALL_DOCS' undefined

Aborting

What the heck? I don't want to install it anywhere, especially system-wide. Can it please just build docs for me to read locally?

Especially, error message in unclear. No environment variables were ever mentioned in --help output. But I roughly guess it depends on --installdir option.

Alternatives

In a certain alternative language, or rather its ecosystem one could type:

cargo doc --open

or even

rustup doc --std

to get all their documentation, right in their browser, without any extra steps or global installation paths.