My custom .direnvrc

.direnvrc

# See https://github.com/direnv/direnv/wiki/Python#-pyenv

use_flutter() {
  PATH_add "$HOME/workspace/flutter/bin"
}

# Python using pyenv
#
# Usage:
# Install python with:
#    pyenv install 3.9.0
# Add to .envrc
#    use python 3.9.0
#
layout_python() {
  local python=${1:-python}
  [[ $# -gt 0 ]] && shift
  local old_env=$(direnv_layout_dir)/virtualenv
  unset PYTHONHOME
  if [[ -d $old_env && $python = python ]]; then
    export VIRTUAL_ENV=$old_env
  else
    local python_version
    python_version=$("$python" -c "import platform as p;print(p.python_version())")
    if [[ -z $python_version ]]; then
      log_error "Could not find python's version"
      return 1
    fi

    export VIRTUAL_ENV=$(direnv_layout_dir)/python-$python_version
    if [[ ! -d $VIRTUAL_ENV ]]; then
      # virtualenv "--python=$python" "$@" "$VIRTUAL_ENV"
      python -m venv "$@" "$VIRTUAL_ENV"
    fi
  fi
  PATH_add "$VIRTUAL_ENV/bin"
}

use_python() {
  local python_root=$HOME/.pyenv/versions/$1
  load_prefix "$python_root"
  if [[ -x "$python_root/bin/python3" ]]; then
    layout python3
  else
    layout python
  fi
}

# nvm
#
# See https://gist.github.com/gudleik/7ae3ef00f42440671f16
# 
# Usage:
# Add to .envrc
#    use node 10.16.3
#
use_node() {
  layout node

  local node_version=$1

  if [ "$node_version" == "package.json" ]; then
    # Requires jq: `brew install jq`
    node_version=`jq --raw-output .engines.node package.json | tr -d "<=> "`
  fi

  local node_path=${NODE_DIR:-$HOME/.nvm/versions/node}
  local nvm_fish="$HOME/.config/nvm"

  if [ -x "$node_path/$node_version/bin/node" ]; then
    PATH_add $node_path/$node_version/bin
  elif [ -x "$node_path/v$node_version/bin/node" ]; then
    # Support nvm users (nvm prefixes versions with 'v')
    PATH_add $node_path/v$node_version/bin
  elif [ -x "$nvm_fish/$node_version/bin/node" ]; then
    # Support nvm.fish - https://github.com/jorgebucaran/nvm.fish
    PATH_add $nvm_fish/$node_version/bin
  else
    echo "!!! Node.js version $node_version is not installed"
  fi
  
  export NODE_PATH=./node_modules
}

# Ruby
# See https://github.com/direnv/direnv/wiki/Ruby#-chruby
#
# Usage:
# Install ruby with: 
#   ruby-install 2.6.8
#
# Add to .envrc file:
#   use ruby 2.6.8
#
use_ruby()
{
  local version
  version="${1}"

  [[ "${version}" == --auto ]] && version="$(read_version_file .ruby-version)"
  [[ -z "${version}" ]] && return

  local chruby

  if has brew; then
    local brew_prefix
    brew_prefix="$(brew --prefix)"

    if [[ -e "${brew_prefix}/opt/chruby/share/chruby/chruby.sh" ]]; then
      chruby="${brew_prefix}/opt/chruby/share/chruby/chruby.sh"
    fi
  fi

  [[ -z "${chruby}" ]] && [[ -e /usr/local/share/chruby/chruby.sh ]] &&
    chruby=/usr/local/share/chruby/chruby.sh

  [[ -z "${chruby}" ]] && return

  echo "${chruby}"
  source "${chruby}"
  chruby "${version}"
}


# Java
#
# See: https://gist.github.com/rnorth/0fd5048da85957da39c17bd49c4ca922
#
# Usage:
#   Add to .envrc file:
#     use java adopt@1.11.0-6
#
use_java() {
    source ~/.jabba/jabba.sh
    
    # Install the required version of Java if not already installed
    if [[ "$(jabba link $1)" == "" ]]; then
        echo "Java $1 is not installed; attempting to install"
        jabba install $1
    fi

    # Set JAVA_HOME, and load the required version of Java onto the path
    export JAVA_HOME=$(jabba link $1)/Contents/Home
    echo "JAVA_HOME=$JAVA_HOME"
    load_prefix "$JAVA_HOME"
}