wooper.dev

A web service that generates Nix flakes with specific package versions from nixpkgs history. Use any version of any nixpkgs package without writing a flake.

Prerequisites

• Nix with flakes enabled

Quick Start

# Enter a shell with specific packages
nix shell "https://wooper.dev/python3;nodejs;ruff"

# Run a package directly
nix run "https://wooper.dev/uv~=0.5.0#uv" -- --version

The first run takes a while as Nix downloads and evaluates the flake. Subsequent runs use the cache.

Version Specifiers

Wooper uses PEP 440 version specifiers:

Specifier	Meaning
uv	Latest available version
uv==0.5.0	Exact version
uv>=0.5.0	Minimum version
uv~=0.5.0	Compatible release (>=0.5.0, <0.6.0)

Note: > and < must be URL-encoded (%3E, %3C) as they break Nix's URL parser.

Multiple Packages

Separate packages with semicolons:

nix shell "https://wooper.dev/python3~=3.12;uv~=0.5.0;ruff"

Wooper optimizes flake inputs by selecting the minimum number of nixpkgs revisions needed to satisfy all version requirements.

Limits:

• Maximum 50 packages per request
• Ambiguous packages like python are rejected—use python2 or python3

Portable Shell Scripts

Generate a standalone shell script that can be committed to your repo:

nix run "https://wooper.dev/uv~=0.5.0;ruff" > dev.sh
chmod +x dev.sh

When run, the generated flake outputs a shell script to stdout (via quickshell). This script fetches packages directly from cache.nixos.org without re-evaluating the flake—anyone with Nix can run it instantly.

Works on aarch64-darwin, x86_64-darwin, aarch64-linux, and x86_64-linux.

Use as a Flake Input

Pin specific package versions in your flake:

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
    wooper.url = "https://wooper.dev/uv~=0.5.0;ruff";
  };

  outputs = { self, nixpkgs, wooper }: let
    system = "aarch64-darwin";
    pkgs = nixpkgs.legacyPackages.${system};
  in {
    devShells.${system}.default = pkgs.mkShell {
      packages = [
        wooper.packages.${system}.uv
        wooper.packages.${system}.ruff
      ];
    };
  };
}

API

Interactive documentation available at wooper.dev/docs.

Endpoints

Endpoint	Description
GET /{packages}	Flake tarball (flake.nix + flake.lock) for nix shell/nix run
GET /flake/{packages}	Raw flake.nix content

Example

# Get flake.nix content
curl "https://wooper.dev/flake/python3~=3.12"

Development

Setup

# Set up database connection
export WOOPER_DB="postgresql://user:password@host/database"

# Fill the packages database (use a recent date to limit initial sync)
uv run -m wooper_dev.updater --after 2025-01-01

# Start dev server
uv run uvicorn wooper_dev.main:app --reload

The updater scrapes Hydra for successful nixpkgs builds and indexes all package versions for each revision.

Testing

uv run pytest

Update quickshell dependency

uv run scripts/update_quickshell.py