Engineering Craft › Developer Tooling

Language Version Manager

Tools like nvm, pyenv or mise for switching language versions.

Also known as: nvm, pyenv, mise, asdf, runtime version manager

Different projects need different versions of a language or tool: one wants Node 18, another Node 22, an older one Python 3.9. A version manager lets you install several versions side by side and switch between them per project or per shell.

nvm install 22
nvm use 22
node --version          # v22.x

pyenv install 3.12.4
pyenv local 3.12.4      # writes .python-version in this folder

Pin the version in the project

Most managers read a small file in the repository, so everyone (and CI) uses the same version:

.nvmrc          →  22
.python-version →  3.12.4
.tool-versions  →  nodejs 22.4.0  python 3.12.4        (asdf, mise)

Also say it in the README and in engines in package.json. A mismatch is a common cause of “works on my machine” (dev environment setup).

Version manager vs other tools

• Version managers choose the language or runtime version.
• Virtual environments and node_modules isolate a project’s libraries, which are separate from the runtime.
• Dev containers and Docker pin everything in an image, an alternative that also covers system packages.

Tips

• Don’t use the system Python or Node for projects. Updating the OS can break them.
• Match production’s version, or at least the same major.
• Reinstall dependencies after switching versions.
• If a command isn’t found after installing, open a new shell, or check that the manager’s setup lines are in your shell profile.