Question about setting up new package environment

General Usage
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I am trying to understand how I can efficiently setup a new package environment. I have the following questions,

  1. When I create a new environment using pkg> activate EnvName - why the folder named EnvName with associated Manifest and Project toml files are not created right away? What do I need to do to have the folder automatically created and populated?

  2. I am trying to understand the documentation about --shared switch of pkg.activate function. From the documentation, When the option --shared is given, path will be assumed to be a directory name and searched for in the environments folders of the depots in the depot stack.

  • Isnā€™t path is always a directory name? (I am assuming all pkg environment is a dedicated folder with some setting in toml file).
  • What does it mean by ā€˜depots in the depot stackā€™?

Can anybody explain what --shared switch does some other way?

Thanks!

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  1. When I create a new environment using pkg> activate EnvName - why the folder named EnvName with associated Manifest and Project toml files are not created right away? What do I need to do to have the folder automatically created and populated?

Iā€™m not sure why they are not created straight away, but they will be created when you add a package to the environment (Pkg.add or Pkg.develop). Iā€™m guessing because there is no information to save until a package is actually added, nothing is created.

  1. I am trying to understand the documentation about --shared switch of pkg.activate function. From the documentation, When the option --shared is given, path will be assumed to be a directory name and searched for in the environments folders of the depots in the depot stack.

The --shared switch looks for/creates environments in a common location, regardless of the working folder. Unless youā€™ve changed the depot location, this will typically be at ~/.julia/enviroments. You can change that location by modifying the depot location.

For example:

(@v1.6) pkg> activate --shared MyEnv
  Activating new environment at `~/.julia/environments/MyEnv/Project.toml`
(@MyEnv) pkg>

If I didnā€™t use the --shared flag, it would just make the environment in my current working folder. The @ symbol infront of the environment name indicates that itā€™s a shared env.

  • Isnā€™t path is always a directory name? (I am assuming all pkg environment is a dedicated folder with some setting in toml file).

When not using a shared environment, path can actually be a directory, e.g.

(MyEnv) pkg> activate MyFolder1/MyFolder2/MyEnv
  Activating new environment at `~/MyFolder1/MyFolder2/MyEnv/Project.toml`

This directory can be relative to current working directory, or absolute.

Note if I try to use a path with a shared environment it fails:

(MyEnv) pkg> activate --shared MyFolder1/MyFolder2/MyEnv
ERROR: not a valid name for a shared environment: MyFolder1/MyFolder2/MyEnv

This is why the docs say ā€œpath will be assumed to be a directory nameā€.

  • What does it mean by ā€˜depots in the depot stackā€™?

The depot stack can be viewed by looking at the DEPOT_PATH variable in Julia. The depots in the depot stack are where the package manager, as well as Juliaā€™s code loading mechanisms, look for package registries, installed packages, named environments, repo clones, cached compiled package images, configuration files, and the default location of the REPLā€™s history file (from the docs)

For me (Mac user), DEPOT_PATH looks like:

julia> DEPOT_PATH
3-element Vector{String}:
 "/Users/username/.julia"
 "/Applications/Julia-1.6.app/Contents/Resources/julia/local/share/julia"
 "/Applications/Julia-1.6.app/Contents/Resources/julia/share/julia"

It can be seen that the first depot in the path is where my shared environment was created above. If I wanted the depot to be elsewhere I could modify this variable by pushing in a new folder.

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