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124 lines
4.2 KiB
Markdown
124 lines
4.2 KiB
Markdown
# Nim {#nim}
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The Nim compiler and a builder function is available.
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Nim programs are built using `buildNimPackage` and a lockfile containing Nim dependencies.
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The following example shows a Nim program that depends only on Nim libraries:
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```nix
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{ lib, buildNimPackage, fetchFromGitHub }:
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buildNimPackage (finalAttrs: {
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pname = "ttop";
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version = "1.2.7";
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src = fetchFromGitHub {
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owner = "inv2004";
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repo = "ttop";
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rev = "v${finalAttrs.version}";
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hash = "sha256-oPdaUqh6eN1X5kAYVvevOndkB/xnQng9QVLX9bu5P5E=";
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};
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lockFile = ./lock.json;
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nimFlags = [
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"-d:NimblePkgVersion=${finalAttrs.version}"
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];
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})
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```
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## `buildNimPackage` parameters {#buildnimpackage-parameters}
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The `buildNimPackage` function takes an attrset of parameters that are passed on to `stdenv.mkDerivation`.
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The following parameters are specific to `buildNimPackage`:
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* `lockFile`: JSON formatted lockfile.
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* `nimbleFile`: Specify the Nimble file location of the package being built
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rather than discover the file at build-time.
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* `nimRelease ? true`: Build the package in *release* mode.
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* `nimDefines ? []`: A list of Nim defines. Key-value tuples are not supported.
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* `nimFlags ? []`: A list of command line arguments to pass to the Nim compiler.
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Use this to specify defines with arguments in the form of `-d:${name}=${value}`.
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* `nimDoc` ? false`: Build and install HTML documentation.
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## Lockfiles {#nim-lockfiles}
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Nim lockfiles are created with the `nim_lk` utility.
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Run `nim_lk` with the source directory as an argument and it will print a lockfile to stdout.
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```sh
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$ cd nixpkgs
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$ nix build -f . ttop.src
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$ nix run -f . nim_lk ./result | jq --sort-keys > pkgs/by-name/tt/ttop/lock.json
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```
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## Overriding Nim packages {#nim-overrides}
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The `buildNimPackage` function generates flags and additional build dependencies from the `lockFile` parameter passed to `buildNimPackage`. Using [`overrideAttrs`](#sec-pkg-overrideAttrs) on the final package will apply after this has already been generated, so this can't be used to override the `lockFile` in a package built with `buildNimPackage`. To be able to override parameters before flags and build dependencies are generated from the `lockFile`, use `overrideNimAttrs` instead with the same syntax as `overrideAttrs`:
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```nix
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pkgs.nitter.overrideNimAttrs {
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# using a different source which has different dependencies from the standard package
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src = pkgs.fetchFromGithub { /* … */ };
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# new lock file generated from the source
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lockFile = ./custom-lock.json;
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}
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```
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## Lockfile dependency overrides {#nim-lock-overrides}
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The `buildNimPackage` function matches the libraries specified by `lockFile` to attrset of override functions that are then applied to the package derivation.
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The default overrides are maintained as the top-level `nimOverrides` attrset at `pkgs/top-level/nim-overrides.nix`.
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For example, to propagate a dependency on SDL2 for lockfiles that select the Nim `sdl2` library, an overlay is added to the set in the `nim-overrides.nix` file:
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```nix
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{ lib
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/* … */
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, SDL2
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/* … */
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}:
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{
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/* … */
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sdl2 =
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lockAttrs:
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{ buildInputs ? [ ], ... }:
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{
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buildInputs = buildInputs ++ [ SDL2 ];
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};
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/* … */
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}
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```
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The annotations in the `nim-overrides.nix` set are functions that take two arguments and return a new attrset to be overlaid on the package being built.
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- lockAttrs: the attrset for this library from within a lockfile. This can be used to implement library version constraints, such as marking libraries as broken or insecure.
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- prevAttrs: the attrset produced by initial arguments to `buildNimPackage` and any preceding lockfile overlays.
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### Overriding an Nim library override {#nim-lock-overrides-overrides}
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The `nimOverrides` attrset makes it possible to modify overrides in a few different ways.
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Override a package internal to its definition:
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```nix
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{ lib, buildNimPackage, nimOverrides, libressl }:
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let
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buildNimPackage' = buildNimPackage.override {
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nimOverrides = nimOverrides.override { openssl = libressl; };
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};
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in buildNimPackage' (finalAttrs: {
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pname = "foo";
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# …
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})
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```
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Override a package externally:
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```nix
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{ pkgs }: {
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foo = pkgs.foo.override {
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buildNimPackage = pkgs.buildNimPackage.override {
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nimOverrides = pkgs.nimOverrides.override { openssl = libressl; };
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};
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};
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}
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```
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