YAML for config

[srid]

This would mitigate #339

Our entire omnix configuration (om.nix),
https://github.com/juspay/omnix/blob/main/nix/modules/flake-parts/om.nix

can be written as YAML as well (see below). This has the benefit of not needing to evaluate the whole flake just to get the omnix config. This would then make om develop faster.

We may still have to support Nix-based config (but that piggyback on YAML using builtins.fromYAML) for cases where we evaluate a non-local flake (even then we can catch the flake in local nix store before looking up YAML, falling back to Nix eval).

Blocked on #341 (after which doing this should be straightforward).

ci:
  default:
    omnix:
      dir: "."
      steps:
        # build:
        #   enable: false
        flake-check:
          enable: false  # Not necessary
        custom:
          om-show:
            type: "app"
            # name: "default"
            args:
              - "show"
              - "."
          binary-size-is-small:
            type: "app"
            name: "check-closure-size"
            systems:
              - "x86_64-linux"  # We have static binary for Linux only.
          omnix-source-is-buildable:
            type: "app"
            name: "omnix-source-is-buildable"
          cargo-tests:
            type: "devshell"
            command:
              - "just"
              - "cargo-test"
            systems:
              - "x86_64-linux"
              - "aarch64-darwin"  # Avoid emulated systems
          cargo-clippy:
            type: "devshell"
            command:
              - "just"
              - "clippy"
            systems:
              - "x86_64-linux"
              - "aarch64-darwin"  # Avoid emulated systems
          cargo-doc:
            type: "devshell"
            command:
              - "just"
              - "cargo-doc"
            systems:
              - "x86_64-linux"
              - "aarch64-darwin"  # Avoid emulated systems
    doc:
      dir: "doc"
    registry:
      dir: "crates/omnix-init/registry"
      steps:
        build:
          enable: false
        custom: {}
    cli-test-dep-cache:
      dir: "crates/omnix-cli/tests"
      steps:
        lockfile:
          enable: false
        flake_check:
          enable: false
        custom: {}
health:
  default:
    nix-version:
      min-required: "2.16.0"
    caches:
      required:
        - "https://om.cachix.org"
    direnv:
      required: true
develop:
  default:
    readme: |
      🍾 Welcome to the **omnix** project

      To run omnix,

      ```sh-session
      just watch <args>
      ```

      (Now, as you edit the Rust sources, the above will reload!)

      🍎🍎 Run 'just' to see more commands. See <https://nixos.asia/en/vscode> for IDE setup.

[srid]

Oh well NixOS/nix#7340

[srid]

even then we can catch the flake in local nix store before looking up YAML, falling back to Nix eval

So this is what we should do, nevermind fromYAML

[shivaraj-bh]

What do we use to parse YAML in rust? I see three options:

• https://github.com/dtolnay/serde-yaml (not maintained anymore)
• https://github.com/chyh1990/yaml-rust (not updated in very long)
• https://github.com/ethiraric/yaml-rust2 (Pure rust impl. unlike the upstream, but not widely used)

[srid]

I'd use serde-yaml for now.

A maintained fork may popup later (there's one already but not ready yet: cafkafk/serde-norway#17). There's also https://github.com/saphyr-rs/saphyr but saphyr-serde is not available yet. So in future we can switch to one of these that the community adopts.

[shivaraj-bh]

Also, what's the problem with using json for configs instead?

[srid]

Not a problem per se, but the UX of editing the config can suck a bit.

https://x.com/i/grok/share/eulnfhBsYG4zrqRX3U96yU9Q6

For eg., multiline-strings will look like this in JSON (forced to be single line, peppered with \n's):

TOML is another option, but nested attrs will look pretty verbose:

---

Do you think we should simply go with JSON instead?

[jayvdb]

re YAML, more options are listed at rustsec/advisory-db#2132 . https://crates.io/crates/serde_yml doesnt use unsafe-libyaml - instead it uses a fork https://github.com/sebastienrousseau/libyml which is actively maintained. I had a problem using it to parse OpenAPI schemas , but it is probably fine with simpler schemas.

[shivaraj-bh]

Basic benchmark of fetching OmConfig from om.nix vs its json equivalent. The benchmark was done using divan on an MBP M1 pro:

Timer precision: 41 ns
config             fastest       │ slowest       │ median        │ mean          │ samples │ iters
├─ from_flake_url  156.5 ms      │ 346.5 ms      │ 173.9 ms      │ 176.2 ms      │ 100     │ 100
├─ from_json       26.16 µs      │ 146.4 µs      │ 29.54 µs      │ 31.53 µs      │ 100     │ 100
╰─ from_yaml       110.4 µs      │ 478.3 µs      │ 115.3 µs      │ 125.5 µs      │ 100     │ 100

Edit: I’m not sure if we’d want to include these benchmarks in juspay/omnix, so they’re in my fork for now. See the implementation.

Edit: I’ll also be adding YAML to this soon.

Edit: The benchmark now includes YAML too