Deprecate environment variable $PREFIX and start looking at $NODE_PREFIX or $NPM_PREFIX to reduce collision potential

[martin-braun]

nvm makes use of $PREFIX to maintain multiple node/npm systems, however Termux (a terminal emulator for Android) also uses $PREFIX in their environment, so Termux and nvm collide. Deprecating the variable on Termux shall be possible, but a lot of third party scripts are out there that use $PREFIX to work within Termux.

The idea is to patch npm (and node) to look for $NODE_PREFIX or $NPM_PREFIX and then falling back to $PREFIX. But: There also need to be a way to disable the fallback legacy $PREFIX so that it can be ignored, if it's set by something else, so it won't disrupt the logic of npm. This way nvm could set work with $NODE_PREFIX or $NPM_PREFIX instead of $PREFIX and Termux could safely continue to use $PREFIX, things wouldn't break.

Ideally, npm gets patched and released with this change for all versions that are shipped with node in the LTS channel as far back as possible. It would be nice to see this happen for npm 9, 8 and 6.

Related issues:

• nvm is not compatible with the "PREFIX" environment variable: currently set to "/usr/local" nvm-sh/nvm#1645
• Termux PREFIX collides with Node/nvm PREFIX termux/termux-app#2096

cc @ljharb @agnostic-apollo @goodevilgenius @GameKyuubi

[ljharb]

To be clear, nvm doesn't set PREFIX, it merely checks it - because if it's set, then npm will look outside of nvm's node directory for global modules.

[martin-braun]

Thanks for clarifying it. Guess I misinterpreted it, although the fix should still work.

[ljharb]

Since npm already looks at NPM_CONFIG_PREFIX, for a long time now, it would be a pretty small breaking change to just drop PREFIX entirely as an env var (even if it was kept in config as “prefix”).