Dump all reachable derivations

[lukego]

I would like to make a simple tool to visualizes a set of derivations e.g. all of the ones in nixpkgs. The tool would allow searching (like nox) but also navigating through build-time and run-time dependencies (like Hydra.)

Question: How can I take a snapshot of all the necessary data such that I can import it into the tool all at once?

I see that nox uses nix-env -qa --json and while this seems to contain much of what I want (list of derivations, their descriptions, some metadata) is does not seem to have everything (e.g. the dependency graph.) I have not found anything more suitable in the nix-store manpage. I wonder if I need to be parsing the .drv files but then the question is how to ensure that all the relevant ones exist and how to identify the subset I am interested in e.g. reachable from the result of import <nixpkgs>.

Tips would be welcome! (This is for the first steps of the Studio project.)

[domenkozar]

@edolstra I remember Hydra does this, but not sure how to get the information with recent refactorings.

[vcunat]

For build-time graph you can get derivation paths nix-env -q --drv-path and then create the graph via nix-store -q --graph.

Runtime dependencies are unknowable until you build the stuff, but you can get output paths nix-env -q --out-path and after building the packages you can even graph on those in the same way.

[lukego]

Thanks for the info! Seems that nix-env -q --attr-path answers what was going to be my follow-on question :).

[lukego]

I did come up with a new question anyway :-). It takes a while to generate this description and I would like to cache it. Can I do that with nix? (Can I use nix-build to create this description of nixpkgs and have it automatically regenerate when stale? Or should I cook up some ad-hoc caching scheme of my own?)

[vcunat]

nox does such things in some way; nix doesn't. I think it would be really difficult to do properly, as there are lots of things that can theoretically affect evaluation – environment variables, your configs, etc.

[stale]

I marked this as stale due to inactivity. → More info