Updated flake documentation #2917
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doc/flakes/design.md
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| @@ -164,14 +155,17 @@ Similarly, a minimal `flake.nix` for Nixpkgs: | |||
| { | |||
| name = "nixpkgs"; | |||
| epoch = 201906; | |||
| epoch = 2019; | |||
doc/flakes/design.md
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| ## Goals | |||
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| * To provide Nix repositories with an easy and standard way to | |||
| reference other Nix repositories. | |||
| * Standard and easy dependency handling in Nix | |||
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This is ambiguous because it doesn't explain what is meant with dependency handling. I mean, Nix has always done "dependency handling" between packages, it just didn't have dependency handling for Nix repos.
doc/flakes/design.md
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| * To allow such references to be queried and updated automatically. | ||
| * Discoverability: Be able to query and update dependencies automatically |
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Idem: this suggests we're querying/updating package dependencies (like the many auto-updates that exist for Nixpkgs).
doc/flakes/design.md
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| * To enable reproducible, hermetic evaluation of packages and NixOS | ||
| configurations. | ||
| * Reproducibility: Evaluate packages and NixOS configurations purely by default |
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"Hermetic" is arguably a more fashionable term.
| * Flakes *provide* an attribute set of values, such as packages, | ||
| Nixpkgs overlays, NixOS modules, library functions, Hydra jobs, | ||
| `nix-shell` definitions, etc. | ||
| * A flake *provides* an attribute set of values, such as packages, Nixpkgs |
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Maybe this should be "A flake outputs"?
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I disagree. I think "to provide" is much clearer. I don't understand what a flake "outputs" would really look like.
doc/flakes/design.md
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| command. That is, commands such as `nix install` ignore all other | ||
| flake attributes. | ||
| * `packages`: A set of installable derivations used by the `nix` command. That | ||
| is, commands such as `nix install` ignore all other flake attributes. |
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Should mention that packages cannot be a nested set.
doc/flakes/design.md
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| * `commitHash` (or `rev`?) (not for tarball flakes): The Git commit | ||
| hash. | ||
| * `devShell`: A specification of a development environment in some TBD format. |
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The format is that it's just a regular derivation.
doc/flakes/design.md
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| * Add a flake attribute to specifiy non-flake dependencies, e.g. | ||
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| > nonFlakeInputs.foobar = github:foo/bar; | ||
| * `self`: The path to the flake's source code |
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This is in fact the result of the flake's output which is passed into itself. So self.outputs.foo should work.
doc/flakes/design.md
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| direnv. | ||
| where `builtins.flakeRegistry` is the global registry with user overrides | ||
| applied, and `builtins.getFlake` downloads a flake and resolves its | ||
| dependencies. | ||
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| ## Pure evaluation and caching | ||
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| Flake evaluation should be done in pure mode. Thus: |
doc/flakes/design.md
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| * Download a precomputed cache | ||
| (e.g. `https://releases.nixos.org/eval/<flake-closure-hash>.sqlite`). So | ||
| a command like `nix search` could avoid evaluating Nixpkgs entirely. | ||
| * Keep a local evaluation cache (say `~/.cache/nix/eval.sqlite`) mapping |
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This is concretly ~/.cache/nix/eval-cache-v1.sqlite now.
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