Add `pixi tree --json`

[ruben-arts]

Problem description

To give better support for marimo's package manager view, we should support json output.

They already support pixi but don't allow for the tree view yet.

[baszalmstra]

Could you maybe briefly give a json schema or example that I could mimic?

[ruben-arts]

To be honest, I can't find a reasonable example. Maybe @manzt has some input for what would make it easier for them.

Side note, it could also be done by extending the pixi list --json to include the "depends" information in a package record. Then it would be simple enough to make the "tree" in code. Which might be enough for now.

[baszalmstra]

It would be nice to get somewhat of a schema here. With a schema it would probably not be hard to implement.

[manzt]

Sorry for the radio silence. Currently in marimo, we parse the output of uv tree, which doesn't have a JSON schema... It seems like there are some pieces of this that avoid showing circular dependencies and other complexities, so it's hard to describe a schema.

So it's a bit of a hack right now. We parse the text output into this structure (marimo/_utils/uv_tree.py):

interface DependencyTreeNode {
  name: string;
  version: string | null;
  tags: Array<{kind: "extra" | "group" | "cycle", value: string}>;
  dependencies: DependencyTreeNode[];
}

The uv tree command has several behaviors that make parsing awkward. Packages already shown in the tree are marked with (*) and their dependencies aren't repeated. The depth can be limited with -d, --depth <DEPTH> (default: 255). The output uses Unicode box-drawing characters that we parse to determine nesting levels, and shows extras/groups inline with package names.

There's some discussion about adding JSON output to uv tree:

• uv pip tree machine readable output astral-sh/uv#4711
• Add support for a JSON output format for machine readable output throughout uv astral-sh/uv#411

[baszalmstra]

That already sounds veeery similar to pixi tree! Have you tried that?

[abkfenris]

I've drafted a JSON output for tree in #4261