Unload hook

[nyarly]

When leaving an .envrc directory, it'd be nice to be able to run a script to undo changes that happened when entering the dir.

For instance, I'm using chruby for use_ruby - so long as I switch from ruby project to ruby project, it's fine, but leaving direnv dirs, I'm left with "whichever ruby I had last" - being able to chruby 2.0 whenever direnv unloads would be handy.

[nyarly]

I guess I could .envrc a chruby in my homedir, huh?

[zimbatm]

How does your use_ruby look like ?

I think that chruby sets environment variables to select the ruby version so direnv should properly revert those changes when going out of the directory. If you're using chruby's auto-switching feature there might be a conflict between direnv and chruby.

[nyarly]

use_ruby(){
  local version=$1
  if [ -z $version ]; then
    version=".ruby-version"
  fi
  if [ -f $version ]; then
    version=$(cat $version)
  fi

  chruby $version
  layout ruby
}

The important part is the chruby - which looks for a matching installed ruby and sets up symlinks for it. I'm specifically not using the chruby/auto.sh script, so my running ruby version doesn't depend on an env var.

Quite reasonably, the answer could be "that's not what direnv is for"...

[zimbatm]

Hey nyarly,

I think you also need to source that chruby.sh file at the start of the use_ruby function. direnv starts a bash sub-shell to evaluate the .envrc and the .bashrc is not supposed to be loaded in that context.
According to https://github.com/postmodern/chruby/blob/master/share/chruby/chruby.sh#L32 chruby is also using environment variables so it should be fine.
Alternatively you can also use load_prefix ~/.rubies/$version instead of chruby.

[nyarly]

load_prefix is an interesting idea.

I think I figured out what happened: I used chruby at the commandline to test something in a different ruby and then left the directory. So direnv didn't change back to the original value of e.g. PATH because PATH had been changed while I was in the dir.

[sknop]

I have another use case for an unload hook.
I update my shell title when I enter a directory under direnv control:

echo -n -e "\033];In DirEnv\007"

It would be great if I could unset this when I leaving the directory again.

[sknop]

Resetting the shell title is exactly the use I am looking for.

[zimbatm]

Hey @sknop, I think you can achieve what you want by changing the PS1 no ?

[zimbatm]

not tested but something like that:

in_direnv() {
  if [ -n "$DIRENV_DIR" ]; then
    echo -n -e "\033];In DirEnv\007"
  else
    echo -n -e "\033];Out of DirEnv\007"
  fi
}
PS1='$(in_direnv) > '

[sknop]

Ah, did not think of using the DIRENV_DIR variable, just discovered that. Not a bad idea, I'll try that.

Thanks

[zimbatm]

Just fixed the script, it's working now

[mattford63]

I have many dirs each has a code base for a different customer. I can launch the appropriate VPN/sshuttle session on entering the dir. But I can't unload it again :-(

[zimbatm]

Hi @mattford63, what would happen if you had two terminals that cd into the same customer folder?

My main issue with implementing the unload hook is that it supposes some sort of system-wide state. The second issue is, what would happen if the terminal is closed? I think this can be fixed but it would be fairly easy to leave the system in an inconsistent state.

[PanisSupraOmnia]

I've got a case where this would be useful as well. In order to work on a Rails project that I'm part of, I need to run bundle exec rake sunspot:solr:start: when I enter the folder. However, once I leave that folder I'd like to bundle exec rake sunspot:solr:stop, because I don't need to leave the solr server running in the background taking up resources. Of course I could simply try to remember to stop it when I'm done with it, but that would kind of defeat the whole point of using direnv for this in the first place.