Nim: Add documentation and GitHub metadata

.github/CODEOWNERS

@@ -225,3 +225,8 @@
 
 # Cinnamon
 /pkgs/desktops/cinnamon @mkg20001
+
+#nim
+/pkgs/development/compilers/nim  @ehmry
+/pkgs/development/nim-packages  @ehmry
+/pkgs/top-level/nim-packages.nix  @ehmry

.github/labeler.yml

@@ -72,6 +72,12 @@
   - nixos/**/*
   - pkgs/os-specific/linux/nixos-rebuild/**/*
 
+"6.topic: nim":
+  - doc/languages-frameworks/nim.section.md
+  - pkgs/development/compilers/nim/*
+  - pkgs/development/nim-packages/**/*
+  - pkgs/top-level/nim-packages.nix
+
 "6.topic: ocaml":
   - doc/languages-frameworks/ocaml.section.md
   - pkgs/development/compilers/ocaml/**/*

doc/languages-frameworks/index.xml

@@ -23,6 +23,7 @@
  <xi:include href="javascript.section.xml" />
  <xi:include href="lua.section.xml" />
  <xi:include href="maven.section.xml" />
+ <xi:include href="nim.section.xml" />
  <xi:include href="ocaml.section.xml" />
  <xi:include href="perl.section.xml" />
  <xi:include href="php.section.xml" />

doc/languages-frameworks/nim.section.md

@@ -0,0 +1,91 @@
+# Nim {#nim}
+
+## Overview {#nim-overview}
+
+The Nim compiler, a builder function, and some packaged libraries are available
+in Nixpkgs. Until now each compiler release has been effectively backwards
+compatible so only the latest version is available.
+
+## Nim program packages in Nixpkgs {#nim-program-packages-in-nixpkgs}
+
+Nim programs can be built using `nimPackages.buildNimPackage`. In the
+case of packages not containing exported library code the attribute
+`nimBinOnly` should be set to `true`.
+
+The following example shows a Nim program that depends only on Nim libraries:
+
+```nix
+{ lib, nimPackages, fetchurl }:
+
+nimPackages.buildNimPackage rec {
+  pname = "hottext";
+  version = "1.4";
+
+  nimBinOnly = true;
+
+  src = fetchurl {
+    url = "https://git.sr.ht/~ehmry/hottext/archive/v${version}.tar.gz";
+    sha256 = "sha256-hIUofi81zowSMbt1lUsxCnVzfJGN3FEiTtN8CEFpwzY=";
+  };
+
+  buildInputs = with nimPackages; [
+    bumpy
+    chroma
+    flatty
+    nimsimd
+    pixie
+    sdl2
+    typography
+    vmath
+    zippy
+  ];
+}
+
+```
+
+## Nim library packages in Nixpkgs {#nim-library-packages-in-nixpkgs}
+
+
+Nim libraries can also be built using `nimPackages.buildNimPackage`, but
+often the product of a fetcher is sufficient to satisfy a dependency.
+The `fetchgit`, `fetchFromGitHub`, and `fetchNimble` functions yield an
+output that can be discovered during the `configurePhase` of `buildNimPackage`.
+
+Nim library packages are listed in
+[pkgs/top-level/nim-packages.nix](https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/nim-packages.nix) and implemented at
+[pkgs/development/nim-packages](https://github.com/NixOS/nixpkgs/tree/master/pkgs/development/nim-packages).
+
+The following example shows a Nim library that propagates a dependency on a
+non-Nim package:
+```nix
+{ lib, buildNimPackage, fetchNimble, SDL2 }:
+
+buildNimPackage rec {
+  pname = "sdl2";
+  version = "2.0.4";
+  src = fetchNimble {
+    inherit pname version;
+    hash = "sha256-Vtcj8goI4zZPQs2TbFoBFlcR5UqDtOldaXSH/+/xULk=";
+  };
+  propagatedBuildInputs = [ SDL2 ];
+}
+```
+
+## `buildNimPackage` parameters {#buildnimpackage-parameters}
+
+All parameters from `stdenv.mkDerivation` function are still supported. The
+following are specific to `buildNimPackage`:
+
+* `nimBinOnly ? false`: If `true` then build only the programs listed in
+  the Nimble file in the packages sources.
+* `nimbleFile`: Specify the Nimble file location of the package being built
+  rather than discover the file at build-time.
+* `nimRelease ? true`: Build the package in *release* mode.
+* `nimDefines ? []`: A list of Nim defines. Key-value tuples are not supported.
+* `nimFlags ? []`: A list of command line arguments to pass to the Nim compiler.
+  Use this to specify defines with arguments in the form of `-d:${name}=${value}`.
+* `nimDoc` ? false`: Build and install HTML documentation.
+
+* `buildInputs` ? []: The packages listed here will be searched for `*.nimble`
+  files which are used to populate the Nim library path. Otherwise the standard
+  behavior is in effect.