`nix-dram`

Nix with a modified frontend, by dramforever

Nix Flake

This repository contains a Nix Flake. To use it, use the following Flake URL:

github:dramforever/nix-dram

The modified Nix is available as defaultApp:

$ nix run github:dramforever/nix-dram -- --version
nix (Nix) 2.4pre20201205_a5d85d0

The binary cache of this flake is available on Cachix. Set it up with:

$ cachix use dram

Check out a list of the contents of this flake.

What is this about?

The main reason of this fork is as follows

As a Nix Flakes user, I was constantly typing nixpkgs over and over again in commands like:

$ nix run nixpkgs#hello
$ nix search nixpkgs hello

See the issue? The Flakes version of Nix does not have an idea of a 'default' flake of any sort. At all. The best you can do is rename nixpkgs to n, but still it frankly sucks.

Introducing nix-dram:

$ nix run hello
$ nix search hello

Now there's no nixpkgs in sight. (You do need to add a default-flake option to your Nix config though.)

Well that's the first thing anyway. It turns out that there were several things I really want to change about Nix, so what I did is just to dump them here. A detailed explanation follows.

What's new?

There are three patches over Nix in this repository:

nix-flake-default.patch: This changes the Nix CLI so that it parses INSTALLABLE arguments differently. The usage of the command nix search was also changed. See below for details.
nix-search-meta.patch: This is not a very user-visible change. It basically alters nix search so that the --json option now dumps the entire meta attribute of the package.

This is mainly used to support nix-search-pretty so that it has more information to work with, but could support other tooling as well.

There is a patch that was removed:

nix-flake-http-redirect.patch: This arose from a thought on how we could keep using the good old channels in Nix Flakes. A quick thought is to just make Nix follow the redirect and save the final redirect target in flake.lock. This is an implementation of that idea.

This was removed because it was already merged into Nix as pull request #4595. See details below.

These changes are incompatible but is predicted to minimally affect current usage. See below for details.

The documentation has not yet been changed to reflect the changes.

Changes to `INSTALLABLE`

An configuration option default-flake is added, which specifies the default flake URL when using the command line interface.

An INSTALLABLE command line argument, such as that of nix run, now has and additional rule when parsing:

If an INSTALLABLE looks like an attribute path, e.g. foo.bar, it is looked up as if it were <default-flake>#foo.bar, where <default-flake> is taken from the config. If the config is unset an error is reported.

'Looks like an attribute path' is defined as fully matching the regular expression [a-zA-Z0-9_"-][a-zA-Z0-9_".-]
Otherwise it is treated as a Flake INSTALLABLE as before.

Command line completion of the new INSTALLABLE syntax is supported.

(In cases where a Flake URL is expected (such as the arguments of --override-flake), the behavior is not changed, i.e. using nixpkgs there still means --override-flake flake:nixpkgs [...] .)

The following table shows the incompatibilities. The 'Legacy compatibility' columns shows a syntax to use that both nix-dram and nixFlakes will interpret according to the column 'Meaning in nixFlakes'. As mentioned above, <default-flake> means the value taken from Nix configuration.

Syntax	Meaning in `nix-dram`	Meaning in `nixFlakes`	Legacy compatibility
`blender`	`<default-flake>#blender`	`flake:blender`	`blender#`
`xorg.xclock`	`<default-flake>#xorg.xclock`	`./xorg.xclock/` (directory)	`./xorg.xclock` or `xorg.xclock/`

One notable example is that if you want to refer to the result symlink from a build output, you will need to specify ./result or result/.

Here are examples of INSTALLABLE syntax that is unaffected:

Syntax	Meaning
`.`	Current directory
`flake:blender`	Flake registry reference to `blender`
`./nix-dram`	The directory `nix-dram` within the current directory
`github:dramforever/nix-dram`	The GitHub repository dramforever/nix-dram
`nixpkgs#hello`	`flake:nixpkgs#hello`

As one can see the change affects a relative small number of use cases, and incompatibilities can be worked around by appending one single character, which even improves readability (though arguably so).

Changes to `nix search`

The nix search command used to have this syntax:

$ nix search [options] INSTALLABLE [KEYWORD]

It now has this syntax:

$ nix search [options] [KEYWORD]

With the INSTALLABLE argument moved into an option, defaulting to that specified in the default-flake option:

  -i, --installable INSTALLABLE     Search within this installable

The following table shows a comparison of use cases, the first of which is predicted to be the most common.

`nix-dram`	`nixFlakes`
`nix search hello`	`nix search default hello`
`nix search -i github:NixOS/nixpkgs hello`	`nix search github:NixOS/nixpkgs hello`
`nix search --expr foo hello`	`nix search --expr foo '' hello`
`nix search --file foo hello`	`nix search --file foo '' hello`

`nix-search` and `nix-search-pretty`

The nix search command, when given the --json option, now dumps the meta attribute of each search result into a JSON property called meta.

{
  "legacyPackages.x86_64-linux.hello": {
    "pname": "hello",
    "version": "2.10",
    "description": "A program that produces a familiar, friendly greeting",
    "meta": {
      "available": true,
      "broken": false,
      "changelog": "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v2.10",
      "description": "A program that produces a familiar, friendly greeting",
      // ...
    }
  },

  // ...
}

nix-search-pretty is an example program that takes in this JSON and produces colorized search output. nix-search is thin wrapper around the two. (Recorded using termtosvg):

nix-search is a wrapper around nix-search-pretty with similar usage to nix search.

Locked HTTP redirects in Flake inputs

(Update: This is already merged into Nix, as PR #4595)

(An issue was discovered with this approach, namely #4672, so this might end up getting reverted. Either case, this patch no longer belongs in nix-dram.)

(Refer to a post on Discourse for discussion.)

How could we refer to good old channels in a Flake URL? Here's a possible way that I thought of:

When a user specifies an http/https URL, and it leads to (possibly several) redirects, we instead record the final redirection destination in flake.lock.
When a flake.lock is consulted to download the tarball, the URL in flake.lock is used.

This way specifying:

inputs.nixpkgs.url = "https://nixos.org/channels/nixos-unstable/nixexprs.tar.xz";

Would actually just work, as instead of failing with an invalid hash whenever nixos-unstable updates, it saves the redirected URL which points to a stable version. flake.nix would look something like this:

{
  "nodes": {
    "nixpkgs": {
      "locked": {
        "narHash": "sha256-N1qI50AkeTSBp1ffUCHrcK2re52wrn6euFFGGvFa2iw=",
        "type": "tarball",
        "url": "https://releases.nixos.org/nixos/unstable/nixos-21.05pre269929.ff96a0fa563/nixexprs.tar.xz"
      },
      "original": {
        "type": "tarball",
        "url": "https://nixos.org/channels/nixos-unstable/nixexprs.tar.xz"
      }
    },
    // ...
}

This way, older versions of Nix seeing this new lock file would just behave as if someone used --override-input, and newer versions of Nix seeing the old lock file with the pre-redirection URL would simply migrate it over when nix flake update --update-input is used.

A major concern would be whether this redirection is actually part of the intended interface of channels.nixos.org.

More on the design

In the usual version of nixFlakes, it is in fact a conscious design choice that you have to type nixpkgs every time. I tried making a feature request but got immmediately shut down, with an explanation that flake:nixpkgs should not be prioritized as a 'default'. I guess flake:default it is? In any case, it seems that the main author is open to improvements, but is not that keen on the idea.

After some discussion with gytis-ivaskevicius, the default flake was made configurable with the config file.

The basic idea of nix-dram is based on a slightly different prediction of how Flakes will be used. Namely, it is predicted that users will create their own personal Flake, referencing other Flakes as inputs. It will possibly provide a package set for use in nix commands, various nixosConfigurations, and so on.

'Smaller' Flakes will exists and possibly even in great numbers, but each user will have their own 'favorite' Flake to be used for most purposes. In nix-dram that flake will be assigned default-flake. This indeed seems to be the use case with popular demonstration repositories such as nixflk showing this approach. Will this be how we use Flakes in the future? We will have to wait and see.

This project is called nix-dram with the specific intention that it will never be official. This is just one person, me, trying out one point in the design space. That's how free software works, isn't it?

Why is this not a script or a few shell functions?

(Reference: https://www.reddit.com/r/NixOS/comments/lbqsfg/_/glvs8zw?context=1)

`INSTALLABLE`

nix-dram handles everything where an INSTALLABLE is expected, so other commands will also work, like nix run, nix eval, nix develop, nix edit. (Yes I do use these all the time.) Even more obscure ones like and nix copy, nix bundle also work.

A wrapper around nix would mean more subcommands I'd feel comfortable implementing, honestly. On the other hand, if you do the C++ work, to modify INSTALLABLE handling, there's just one function you absolutely need to touch, namely SourceExprCommand::parseInstallables:

Another thing is compatibility with the old syntax. In the case of a wrapper, it could be possible to be allow for both 'implicit flake' and 'explicit flake' INSTALLABLE to work together as described in 'Changes to INSTALLABLE', but it is going to be much more handling.

A script would need to look at each INSTALLABLE argument and translate those that need translating. Figuring out which arguments are INSTALLABLE is actually the hardest part. A wrapper would need to either understand all the options or require something like a -- marker, otherwise it could accidentally change --override-flake foo bar into --override-flake <default-flake>#foo <default-flake>#bar.

Command line completion

nix-dram also handles command line completion, so if you type nix search wires and press tab, you get wireshark. Not having to type nixpkgs#wires makes it much smoother. Conceivably you can write your completion handlers as well, but that's honestly way too much for me.

That's because nix the program itself handles command line completion. If you write a wrapper, you need to to translate completion requests/responses (Yes, responses as well if you don't want wires completing to <default-flake>#wireshark). You may even need to call nix twice to generate completion for both the registry and attributes. It seems much more work than just patching whatever generates the completion. And the problem of handling options also occurs here.

Are you sure this is the best way?

I like how much I get from the moderate amount of patching I did. The main drawback I find is that I need to spend quite a bit of time building nix-dram. I honestly think it's worth it.

But what if...

If you think nix-dram is too much, you can write your own little scripts. nix-dram might just not be what you need.

If you like specifying the flake all the time, then by all means just use the usual Nix Flakes CLI.

If you have any idea on how what nix-dram does could be done in a more lightweight way, I'm happy to take suggestions.

Contents of this flake

$ nix flake show github:dramforever/nix-dram
github:dramforever/nix-dram/[...]
├───apps
│   ├───aarch64-linux
│   │   ├───nix-dram: app
│   │   └───nix-dram-progress: app
│   ├───i686-linux
│   │   ├───nix-dram: app
│   │   └───nix-dram-progress: app
│   ├───x86_64-darwin
│   │   ├───nix-dram: app
│   │   └───nix-dram-progress: app
│   └───x86_64-linux
│       ├───nix-dram: app
│       └───nix-dram-progress: app
├───checks
│   ├───aarch64-linux
│   │   ├───nix-dram: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│   │   ├───nix-dram-progress: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│   │   ├───nix-nar-listing: derivation 'nix-nar-listing-0.1.0.0'
│   │   ├───nix-search: derivation 'nix-search'
│   │   └───nix-search-pretty: derivation 'nix-search-pretty-0.1.0.0'
│   ├───i686-linux
│   │   ├───nix-dram: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│   │   ├───nix-dram-progress: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│   │   ├───nix-nar-listing: derivation 'nix-nar-listing-0.1.0.0'
│   │   ├───nix-search: derivation 'nix-search'
│   │   └───nix-search-pretty: derivation 'nix-search-pretty-0.1.0.0'
│   ├───x86_64-darwin
│   │   ├───nix-dram: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│   │   ├───nix-dram-progress: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│   │   ├───nix-nar-listing: derivation 'nix-nar-listing-0.1.0.0'
│   │   ├───nix-search: derivation 'nix-search'
│   │   └───nix-search-pretty: derivation 'nix-search-pretty-0.1.0.0'
│   └───x86_64-linux
│       ├───nix-dram: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│       ├───nix-dram-progress: derivation 'nix-dram-2.4pre20201205_a5d85d0'
│       ├───nix-nar-listing: derivation 'nix-nar-listing-0.1.0.0'
│       ├───nix-search: derivation 'nix-search'
│       └───nix-search-pretty: derivation 'nix-search-pretty-0.1.0.0'
├───defaultApp
│   ├───aarch64-linux: app
│   ├───i686-linux: app
│   ├───x86_64-darwin: app
│   └───x86_64-linux: app
├───defaultPackage
│   ├───aarch64-linux: package 'nix-dram-2.4pre20201205_a5d85d0'
│   ├───i686-linux: package 'nix-dram-2.4pre20201205_a5d85d0'
│   ├───x86_64-darwin: package 'nix-dram-2.4pre20201205_a5d85d0'
│   └───x86_64-linux: package 'nix-dram-2.4pre20201205_a5d85d0'
├───overlay: Nixpkgs overlay
└───packages
    ├───aarch64-linux
    │   ├───nix-dram: package 'nix-dram-2.4pre20201205_a5d85d0'
    │   ├───nix-dram-progress: package 'nix-dram-2.4pre20201205_a5d85d0'
    │   ├───nix-nar-listing: package 'nix-nar-listing-0.1.0.0'
    │   ├───nix-search: package 'nix-search'
    │   └───nix-search-pretty: package 'nix-search-pretty-0.1.0.0'
    ├───i686-linux
    │   ├───nix-dram: package 'nix-dram-2.4pre20201205_a5d85d0'
    │   ├───nix-dram-progress: package 'nix-dram-2.4pre20201205_a5d85d0'
    │   ├───nix-nar-listing: package 'nix-nar-listing-0.1.0.0'
    │   ├───nix-search: package 'nix-search'
    │   └───nix-search-pretty: package 'nix-search-pretty-0.1.0.0'
    ├───x86_64-darwin
    │   ├───nix-dram: package 'nix-dram-2.4pre20201205_a5d85d0'
    │   ├───nix-dram-progress: package 'nix-dram-2.4pre20201205_a5d85d0'
    │   ├───nix-nar-listing: package 'nix-nar-listing-0.1.0.0'
    │   ├───nix-search: package 'nix-search'
    │   └───nix-search-pretty: package 'nix-search-pretty-0.1.0.0'
    └───x86_64-linux
        ├───nix-dram: package 'nix-dram-2.4pre20201205_a5d85d0'
        ├───nix-dram-progress: package 'nix-dram-2.4pre20201205_a5d85d0'
        ├───nix-nar-listing: package 'nix-nar-listing-0.1.0.0'
        ├───nix-search: package 'nix-search'
        └───nix-search-pretty: package 'nix-search-pretty-0.1.0.0'

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README.md

README.md

`nix-dram`

Nix Flake

What is this about?

What's new?

Changes to `INSTALLABLE`

Changes to `nix search`

`nix-search` and `nix-search-pretty`

Locked HTTP redirects in Flake inputs

More on the design

Why is this not a script or a few shell functions?

`INSTALLABLE`

Command line completion

Are you sure this is the best way?

But what if...

Contents of this flake

Files

README.md

Latest commit

History

README.md

File metadata and controls

nix-dram

Nix Flake

What is this about?

What's new?

Changes to INSTALLABLE

Changes to nix search

nix-search and nix-search-pretty

Locked HTTP redirects in Flake inputs

More on the design

Why is this not a script or a few shell functions?

INSTALLABLE

Command line completion

Are you sure this is the best way?

But what if...

Contents of this flake

`nix-dram`

Changes to `INSTALLABLE`

Changes to `nix search`

`nix-search` and `nix-search-pretty`

`INSTALLABLE`