feat: Add `target-environments-directory` to the global config

[ruben-arts]

Fixes: #997

Todo:

• [x] Fix tests
• [x] Add warning on already local to project installed environments
• [x] Add documentation
• [x] Add symlink from target directory folder to local .pixi folder.

[pavelzw]

We should probably also print a warning when we already see a populated .pixi directory to remove it because this setting is set. Also, we might want to think about printing a warning when we see symlinks? For example, your mounted devcontainer might have this setting enabled but locally you don't want this behavior. (although there are better options in general for pixi in devcontainers as elaborated in https://github.com/prefix-dev/pixi/issues/997#issuecomment-2018525722)

[ruben-arts]

@pavelzw What do you mean with warning when symlinking?

[pavelzw]

What do you mean with warning when symlinking?

When I have a filled .pixi directory instead of a symlink already present, we should warn the user instead of directly deleting it.

[ruben-arts]

This PR move the complete .pixi dir to the specified target dir. But I see a situation where it makes sense to only move the "heavy" environments. So would it make sense to only move the .pixi/envs to the target? @pavelzw @baszalmstra?

Currently it is already weird as you can specify the configuration in the projects .pixi folder but then symlinking it is not possible.

[ruben-arts]

@baszalmstra I looked at all your review points and updated the symlink function a little to also do something on windows. With adding a README.txt file to the .pixi folder to tell the user looking there that it was moved.

[ruben-arts]

Fixed the unknown field issue:

Not sure yet why we run the config parsing twice.

[wolfv]

A few thoughts that came up:

This configuration option is hard to "disable" locally since it mixes two things:

• I want my .pixi folder external
• Where to put the .pixi folders

My proposal would be to split the two options into something like the following:

external-pixi-folder = false  # or true (false is default)
external-pixi-folder-location = "/some/path/pixi-root"  # (path to pixi folder root thingy)

The external-pixi-folder-location would, by default, be inside the global pixi folder, e.g. under:

~/.pixi/pixi-envs-v1/<project-name>-<hash>/...

or we could also drop it next to the package cache (although I am unsure wether a "cache" location is the right place). On the other hand, it "is" a cache since the definition is in the lockfile).

The benefit of having the pixi envs next to the cache would be that hard linking should be possible under most configurations (while the home folder might be on a different partition, or NFS, etc.).

[ruben-arts]

This configuration option is hard to "disable" locally since it mixes two things:

For documentation of thoughts, I believe these shouldn't be two things. You either want to move it or you don't. I can't see a situation where defining both has a beneficial experience as it is not explicit what it will be doing when you have those two defined but set to false.

What about this, we kinda keep the same for the global config, just a rename. ~/.config/pixi/config.toml:

pixi-folder-location = "/etc/pixi_environments"  

Allow for relative paths in this configuration. ~/myproject/.pixi/config.toml:

# This just overrides the global configuration.
pixi-folder-location = "."  

The only problem with that is that we move the complete .pixi folder to the new location. Thus a config.toml will also needs to move with the current design.

Sidenote: the name is not the best yet, as we pixi-folder might make users think its the ~/.pixi folder which listens to $PIXI_HOME.

[chawyehsu]

I'm thinking of the same idea of:

My proposal would be to split the two options into something like the following:

external-pixi-folder = false # or true (false is default) external-pixi-folder-location = "/some/path/pixi-root" # (path to pixi folder root thingy)

but instead using just one config

/// Option to toggle project environments to be detached from the project directory
#[serde(untagged)]
enum DetachedEnvironments {
    Boolean(bool),
    Path(PathBuf),
}

detached-environments = Option<DetachedEnvironments>
//
// - None/Some(false): the default behavior, envs stored within `<project_root>/.pixi`
// - Some(true): toggle detached environments on, envs stored within `<pixi_cache_dir>/envs/<hash(project-x)>`
//    * `<pixi_cache_dir>` would be `XDG_CACHE_HOME/pixi` or its synonym
//    * By storing envs in `pixi_cache_dir` it is possible to leverage command like `pixi clean`/`pixi cache clean`
//      or whatever command we will introduce to clean up caches with envs. It could be configurable, e.g.
//      `pixi clean --[no-]envs`
// - Some(my_path): toggle detached environments on, envs stored in `my_path/<hash(project-x)>`

This would be much more configurable yet concise and only one key is added.

And later you can use pixi config set detached-environments true --global to enable it globally, then use pixi config set detached-environments '/path/to/nfs/pixi-envs-location' --local to explicitly config it to somewhere else for specific projects. The project-level config.toml can even be committed to the project repo for sharing the configuration of env location, would be especially convenient for shared envs I believe - and this is why I think config.toml should not be moved out of .pixi togtther with envs.

[ruben-arts]

@chawyehsu We all like your idea! I'm going to implement it like that including only moving the .pixi/envs folder and not the complete .pixi folder.