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100 lines
2.3 KiB
Markdown
100 lines
2.3 KiB
Markdown
# flake-utils
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**STATUS: alpha**
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Pure Nix flake utility functions.
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The goal of this project is to build a collection of pure Nix functions that don't
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depend on nixpkgs, and that are useful in the context of writing other Nix
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flakes.
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## Usage
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### `defaultSystems -> [<system>]`
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A list of all the systems supported by the nixpkgs project.
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Useful if you want add additional platforms:
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```nix
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eachSystem (defaultSystems ++ ["armv7l-linux"]) (system: { hello = 42; })
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```
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### `eachSystem -> [<system>] -> (<system> -> attrs)`
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A common case is to build the same structure for each system. Instead of
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building the hierarchy manually or per prefix, iterate over each systems and
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then re-build the hierarchy.
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Eg:
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```nix
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eachSystem ["x86_64-linux"] (system: { hello = 42; })
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# => { hello.x86_64-linux.hello = 42; }
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```
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### `eachDefaultSystem -> (<system> -> attrs)`
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`eachSystem` pre-populated with `defaultSystems`.
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### `mkApp { drv, name ? drv.pname or drv.name, execPath ? drv.passthru.execPath or "/bin/${name}"`
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A small utility that builds the structure expected by the special `apps` and `defaultApp` prefixes.
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### `flattenTree -> attrs -> attrs`
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Nix flakes insists on having a flat attribute set of derivations in
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various places like the `packages` and `checks` attributes.
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This function traverses a tree of attributes (by respecting
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recurseIntoAttrs) and only returns their derivations, with a flattened
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key-space.
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Eg:
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```nix
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flattenTree { hello = pkgs.hello; gitAndTools = pkgs.gitAndTools }
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```
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Returns:
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```nix
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{
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hello = «derivation»;
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"gitAndTools/git" = «derivation»;
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"gitAndTools/hub" = «derivation»;
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# ...
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}
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```
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## Example
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Here is how it looks like in practice:
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[$ example/flake.nix](example/flake.nix) as nix
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```nix
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{
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description = "Flake utils demo";
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inputs.flake-utils.url = "github:numtide/flake-utils";
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outputs = { self, nixpkgs, flake-utils }:
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flake-utils.lib.eachDefaultSystem (system:
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let pkgs = nixpkgs.legacyPackages.${system}; in
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rec {
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packages.hello = pkgs.hello;
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defaultPackage = packages.hello;
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apps.hello = flake-utils.lib.mkApp { drv = packages.hello; };
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defaultApp = apps.hello;
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}
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);
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}
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```
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## Known issues
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```
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$ nix flake check
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warning: unknown flake output 'lib'
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```
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nixpkgs is currently having the same issue so I assume that it will be
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eventually standardized.
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