only-allow restricts installation of package as a dependency when the parent uses an alternate package manager.

[CxRes]

As discussed over at discord.

When only-allow is set in a package as a preinstall script, it prevents other packages from installing the given package using an alternate package manager.

For example: if in a package foo with package.json:

{
  ...
  "scripts": {
    "preinstall": "npx -y only-allow pnpm",
    ...
  }
} 

then not only can I not do npm install in foo (well if I disregard the bugs in npm v7 which seems to run install before preinstall), I seem to be unable to do in a package bar npm install foo.

Running only allow as a prepare script is also not suitable because:

• only-allow will unnecessarily be run during publish, and
• npm install git://path/to/foo.git inside bar will be stopped.

only-allow should only restrict package managers when running npm install in the package itself!

[CxRes]

It turns out that npm install has a very unintuitive behavior. According to the folks at npm in an issue I filed with them:

preinstall is a script that runs before the install script, not before the install action. This was discussed in a PR where we proposed changing it, but realized it would be a breaking change: #2713

With this the case, I am not sure how only-allow functionality can even be made to work, no matter which script you use? Any advice (even not a fix) is appreciated.

[golergka]

Just ran into this exact problem here: JichouP/electron-typescript-ipc#1