[php-wasm] Add support for rm command in sandboxed spawn handler

[Utsav-Ladani]

Motivation for the change

The wp plugin uninstall <plugin-name> command uses rm -rf to delete the plugin files, and the current sandboxed spawn handler doesn't have support for it, so I am just adding it.

Closes: #2653

Implementation details

Adding support for rm in the sandboxed spawn handler.

Testing Instructions (or ideally a Blueprint)

The following blueprint should run without any error, and the Hello Dolly plugin should be deleted:

{
  "login": true,
  "landingPage": "/wp-admin/plugins.php",
  "steps": [
    {
      "step": "wp-cli",
      "command": "wp plugin uninstall hello"
    }
  ]
}

[zaerl]

Are we sure we want to run a rm -rf just because the target is a directory? It can be pretty dangerous. @adamziel, what do you think?

[Utsav-Ladani]

WP CLI is also using rm -rf to delete plugin files, so just replicate similar behavior. However, we can add support for flags like r and f, but playground is not using this anywhere else as of now.

[Utsav-Ladani]

But I am newbie in playground 😅, so let me know if I am missing something.

[adamziel]

Good spot @zaerl! Normally, when you run rm <path> it only removes a file. Removing a directory requires passing additional flags as you've both mentioned: -rf. However, this implementation of rm does not check for those flags and it will always remove the entire directory tree if a <path> points to it. Therefore we may want to check for the presence of-rf flags and, if they're missing, refuse to remove a directory. That should make it safer, and that's also what the linux rm would do.

[Utsav-Ladani]

Thanks @zaerl and @adamziel. I have updated the PR based on your suggestion.

[adamziel]

It may be more involved than that. Here's a few examples that would be really useful to cover with a unit test to make sure this command can handle them without failing:

rm file1 file2 file3
rm -r -f directory
rm file1 -f file2 -r
# This one means "remove a file called "-rf"
rm -- -rf
# This one means "recursively remove a file or a directory called "-rf"
rm -rf -- -rf

[Utsav-Ladani]

@adamziel @zaerl What do you think about using the yargs-parser npm package to parse the args instead of writing a custom parser from scratch?

[adamziel]

@Utsav-Ladani potentially! Let's give it a try and see what would this code look like with yargs-parser in place. It seems to be larger than we need, but still fairly small so perhaps? Note this package (@php-wasm/universal) can be imported in both node.js and web browser code, which yargs-parser seems to support. Also, one potentially relevant difference is that yargs-parser seems to accept a string, and in here we already have access to a pre-parsed args array where string syntax were already processed (e.g. "my string" becomes my string) – hopefully there's a way to work from there without re-encoding that and re-escaping quotes.