Support for npm packages or better documentation

[iilyak]

I am trying declaratively install an npm package and created

description = "OpenSpec CLI (installed via npm during Hermit install)"

binaries = ["OpenSpec-${version}/bin/openspec.js"]

# Basic test to validate the package after installation
test = "bin/openspec --help"

source = "https://github.com/Fission-AI/OpenSpec/archive/refs/tags/v${version}.zip"

repository = "https://github.com/Fission-AI/OpenSpec"

version "0.16.0" {
  runtime-dependencies = ["node-24.12.0"]
  on install {
    run {
      cmd = "${HERMIT_BIN}/npm install --prefix ${root} @fission-ai/openspec@${version} --no-fund"
    }
  }
}

I tried different prefix and none of the approaches seem to work:

1. if --prefix ${root} - EACCES: permission denied, mkdir '/Users/iilyak/Library/Caches/hermit/pkg/openspec-0.16.0/node_modules'
2. if --prefix ${HERMIT_ENV}/.hermit/node - the installation succeed but execution fails Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/Users/iilyak/Library/Caches/hermit/pkg/openspec-0.16.0/OpenSpec-0.16.0/dist/cli/index.js'
3. if --prefix ${HERMIT_ENV} - the installation succeed but execution fails Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/Users/iilyak/Library/Caches/hermit/pkg/openspec-0.16.0/OpenSpec-0.16.0/dist/cli/index.js'
4. if I remove --prefix - EACCES: permission denied, mkdir '/Users/iilyak/Library/Caches/hermit/pkg/openspec-0.16.0/node_modules'

ls -la /Users/iilyak/Library/Caches/hermit/pkg/
total 0
drwxr-xr-x  7 iilyak  staff  224 Dec 11 12:45 ./
drwxr-xr-x  8 iilyak  staff  256 Dec  9 12:36 ../
drwxr-xr-x  3 iilyak  staff   96 Dec  9 12:31 hermit@stable/
dr-x------  9 iilyak  staff  288 Dec 11 12:13 node-24.12.0/
dr-x------  3 iilyak  staff   96 Dec 11 12:45 openspec-0.16.0/

[alecthomas]

Correct. Packages are deliberately immutable, though this only occurs after installation - ie. it is mutable while installing