Nixpacks Node.js Build Fails with .nvmrc File Containing Non-Numeric Version (e.g., lts/iron)

[aliesenli]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When attempting to build a Node.js project with Nixpacks, the build fails if there is an .nvmrc file that contains a version string like lts/iron. It seems that the code only recognizes versions in the format (e.g., 20.13.1), but nvmrc files may contain other valid formats such as lts/iron.

Current behaviour:
The build fails because the version string in the .nvmrc file is not recognized if its a string (lts/iron) and throws following error:

Syntax error: unexpected token "T_BASIC_UNESCAPED" at line 1 with value ": node version lts/iron is not valid

To reproduce

1. Add an .nvmrc file with the content specifying a version as string like lts/iron.
2. Try to build with Nixpacks.

Environment

Nixpacks: v1.28.1