nixos-and-flakes-book/docs/other-usage-of-flakes/inputs.md

Flake Inputs

The inputs section in flake.nix is an attribute set used to specify the dependencies of the current flake. There are various types of inputs, as shown in the examples below:

{
  inputs = {
    # GitHub repository as the data source, specifying the master branch.
    # This is the most common input format.
    nixpkgs.url = "github:Mic92/nixpkgs/master";
    # Git URL, applicable to any Git repository using the https/ssh protocol.
    git-example.url = "git+https://git.somehost.tld/user/path?ref=branch";
    # Archive File URL, needed in case your input use LFS.
    # Regular git input doesn't support LFS yet.
    git-example-lfs.url = "https://codeberg.org/solver-orgz/treedome/archive/master.tar.gz";
    # Similar to fetching a Git repository, but using the ssh protocol
    # with key authentication. Also uses the shallow=1 parameter
    # to avoid copying the .git directory.
    ssh-git-example.url = "git+ssh://git@github.com/ryan4yin/nix-secrets.git?shallow=1";
    # It's also possible to directly depend on a local Git repository.
    git-directory-example.url = "git+file:/path/to/repo?shallow=1";
    # Using the `dir` parameter to specify a subdirectory.
    nixpkgs.url = "github:foo/bar?dir=shu";
    # Local folder (if using an absolute path, the 'path:' prefix can be omitted).
    directory-example.url = "path:/path/to/repo";

    # If the data source is not a flake, set flake=false.
    # `flake=false` is usually used to include additional source code,
    #   configuration files, etc.
    # In Nix code, you can directly reference files within
    #   it using "${inputs.bar}/xxx/xxx" notation.
    # For example, import "${inputs.bar}/xxx/xxx.nix" to import a specific nix file,
    # or use "${inputs.bar}/xx/xx" as a path parameter for certain options.
    bar = {
      url = "github:foo/bar/branch";
      flake = false;
    };

    sops-nix = {
      url = "github:Mic92/sops-nix";
      # `follows` is the inheritance syntax within inputs.
      # Here, it ensures that sops-nix's `inputs.nixpkgs` aligns with
      # the current flake's inputs.nixpkgs,
      # avoiding inconsistencies in the dependency's nixpkgs version.
      inputs.nixpkgs.follows = "nixpkgs";
    };

    # Lock the flake to a specific commit.
    nix-doom-emacs = {
      url = "github:vlaci/nix-doom-emacs?rev=238b18d7b2c8239f676358634bfb32693d3706f3";
      flake = false;
    };
  };

  outputs = { self, ... }@inputs: { ... };
}